Technical Articles

How much ink can we deposit on a T-Shirt - Joe Clarke

Wed, 25 Apr 2012 21:18:59 +0530

How much Ink?
The mathematics required to compute how much ink we deposit on a T-shirt are elementary, in contrast the methods to ensure the accuracy of that number are a bit more complex. The four methods listed highest to lowest by accuracy are; 1) real-time 2) cut & weight 3) digital characterization and 4) computation. The cost in time is directly proportional to the precision of each method but before we discuss the details let's first define the ground rules.

The first 3-rules of screen-printing The first rule of screen-printing is “we can't print on air” and yet most T-shirts are 15% to 25% fabric mass which means MOST of the garment is air space! The second rule is “the substrate must be flat” they look flat and they feel flat but they're not flat! Jersey knit is a series of complex knots [which would challenge the skills of most naval men in order to entrap air and to absorb perspiration for wearer-comfort—it's like a “sponge” and as such it is so very difficult to consistently squeeze to the precise middle of a sponge. The third rule is “the ink transfer process should be tailored to the substrate” yet every day with reckless abandon we print on our co-substrate; the rough, absorbent, compressible garment, AND concurrently on the smoother, repellant, rigid flash-cured under-base…we print two extremely different substrates at the same time!.

The violation of these three principles is why it is so demanding to predict a consistent, quality print on a T-Shirt; for the very same reasons it makes ink estimation quite tedious.

Estimating; Tolerances
The reason no one can [accurately] tell you how much ink you'll need for a given press-run is because the applications vary so radically. Before we discuss how to estimate the volume given the conditions in our shop let's take a look at the table above to compare the extreme print parameters which will consume either less or more ink.

Each of the core variables comes to into play; the color contrast between the ink and the garment, the construction of the garment, the mesh geometry and tension, the stencil [if the image is high-resolution], the nature and settings of both the fill blade and the transfer blade plus their respective speeds [always strive for maximum stroke speeds on both] and finally whether the ink is printed directly on the garment or if it lands on a flash-cured under-base. Each of these has a significant influence on ink consumption.

1. Computation [fastest but most approximate]
With an excel spreadsheet, a calculator or pencil and paper it is a matter of simple math to estimate the per color cost of ink on a T-Shirt. The hypothetical specifications for the table below is 35cm wide x 40cm tall = 1400cm2 or 0.14m2 of image area. Our image is single color; high to medium key [spatial frequency] and estimated to be 35% coverage. It will print through a 43/80 screen mesh, requires ~4500pL delivery for a wet film thickness of 90 micron and it will thereby print 346 shirts per kilo. The calculation is shown below.

The price to the end user for imported plastisol ranges between Rs. 400/kg and Rs. 800/kg so the cost per 1400 cm2 image printed through a 43/80 mesh would range between Rs. 1.2/print and Rs. 2.3/print. If our estimates on percentage coverage and ink deposit are accurate so will be the calculation.

2. Digital Characterization
This method is used to fine-tune the percentage coverage in step one above. We will first need access to Adobe Photoshop and a digital version of the artwork to be printed. Step by step instructions follow:
a. Open the image in Photoshop
b. Remove any background by “masking” or “selection”
c. JPEG files need to have background removed
d. PNG files have no background
e. Then trim close to the image as possible (circumscribe in square or rectangle )
f. SELECT [CNTRL click on layer]
g. WINDOW>HISTOGRAM see under pixels size of area
h. Note the number of pixels [Ex: 500,000 pixels]
i. CNTRL D to unselect, GO TO HISTOGRAM
j. Click on box with arrow, change selection to “Entire Image”
k. Note the number of pixels [Ex: 175,000 pixels]
l. ON a calculator divide pixels in #6 by pixels in #9 = [Ex: 35% coverage]

If the ink deposit is estimated accurately [via either wet or dry gauges or other methods] this method will be very precise when used to estimate quantity [prints per kilogram] as well as cost per print. Note: there are simple methods to compute process color [CMYK, index and simulated] images as well but they must include primary, secondary, tertiary and quaternary color along with additivity and are thereby outside the scope of this article.

3. Cut & Weigh
The third method is to die-cut a piece of the garment and use the same die to cut a full coverage printed swatch. We will use a gram scale but first we'll weigh the prints to compare, we MUST ensure both pieces have acclimated to the temperature and relative humidity. Say we have a cotton shirt, the moisture regain of cotton is about 35%, if we weigh one which was just taken off of the shelf and weigh another which just exited from the dryer we will get a false-positive. The difference in the two swatches is the grams per print of the ink at that area. We can run the same test with two [printed & unprinted] garments with somewhat less accuracy. Allow the shirts several hours to acclimate and consider weighing multiple prints to improve the precision of the test.

4. Real time [episode specific but precise]
This method will not help if you need a cost estimate before the run, however it is very accurate. Weigh each kg used for the order BEFORE the press run, then count the shirts printed and weigh the left over ink. Now we have a precise number for the specific image, garment, pre-press and press conditions.

5. Rs./kg ~ Rs./print ~ Rs./real cost?
Before we invest too much time in computing the ink cost per shirt, let's consider the zero-sum cost of conversion. Doing so will help us look not only at the cost of a kilo of ink or the cost per print but the real cost of the ink. It is very easy to make a cheap ink, it is a bit more difficult to make a high quality ink but it is rare if ever the lowest price is given to the ink with the best performance. We want our criteria for “ink quality” to be the cost of the ink on the print PLUS the cost of putting it on the shirt! And the inks called “cheaper” almost ALWAYS cost more than their meager savings in protracted downtime and incremental scrap rate.

A hypothetical contract printer spends Rs. 2,222,531 per month, operates 173 hours per month and has 1 automatic press only. [Note: contract printers do not buy, print and re-sell the garment]. This single press will be fiscally responsible for Rs 12,847 per hour. Our automatic shop cycles at 700 shirts per hour @60% runtime [~40% downtime] and for the year estimates they operate at 70% shop capacity. As a result the fiscal responsibility of the single automatic press is equal to Rs. 12,847 per hour if we divide by average production of 294/Hr, the fiscal cost each is Rs. 44/print.

What we have determined so far in our hypothetical shop is the cost of the cost of ink per shirt is between Rs. 1.20 & Rs. 2.30 and the fiscal responsibility of the single automatic is Rs. 44 per print. So the ink cost is between 2.7% and 5.2% of the fiscal cost. Armed with this information we can make an informed decision by comparing; how much time a “cheap” ink can cost to how many rupees an “expensive” ink will save. Let's say the cheap ink at Rs. 400 will net 294 prints per hour as identified above, the expensive ink cost Rs. 800; TWICE AS MUCH as the cheap ink! Here is the reality of the cost of the ink; in order for us to afford the “expensive ink” we MUST print eight [8] shirts per hour more than we can produce with the cheap ink! The evidence is given immediately below.

*Printing more than 8-extra shirts/hr with quality ink is incrementally profitable!
Note: the 8-shirt minimum increase to pay for the “expensive” ink does not include or account for the increase in press capacity, incremental predictability or consistency, the improvement in quality or the opportunity to increase one's margins.

But before you take a leap of faith and decide to go for the best ink, let's consider the fiscal areas of our operation. There are five areas of zerosum production cost; 1) Setup 2) Time-to-color 3) Cyclerate 4) Stoppage and 5) Scrap-rate. If the ink is tacky and sticky it will require more pressure, cause a shift in the SHAPE of the image and can't be fitted to other colors. If the ink is too thin and traps poorly it is likely to extend “fiddling” time to achieve accurate color. If the ink is tacky it will be difficult to print at maximum speed. If the ink blurs, builds-up, chokes or dries in it will devastate our bottom line output. Finally if the ink requires more pressure it will pop the screen and if it changes viscosity in production it is very likely to ruin some garments. Remember our hypothetical shop spends about 19 times more on time [zero-sum] than on ink…and that's the “expensive” ink! Wishing you all the best; an increase in your ink costs.

(All five sample shirts are photographs of black T-Shirts masterfully printed by and reprinted with the courtesy of Anderson Studio of Nashville, Tennessee USA.)

Root cause and print analysis in 4 color process - Mike Ruff

Wed, 25 Apr 2012 21:18:43 +0530

Introduction:
In print production of 4-colour process screen printing the most critical time associated with producing a profitable job is in the time it takes to achieve the desired color result. Taking too long to analyze print colour problems are mostly caused by a lack of knowledge and poor methodology for quickly determining the cause of colour matching issues. You must have the correct data and the knowledge of how to use it to quickly make the right move the first time. Not understanding this quickly adds up to hundreds of hours of lost press time every year. It causes the daily schedule to always be lagging behind. It causes overtime that is never added to the customer's bill. Profits (and our family times) are challenged when it causes us to work weekends for free.

In this short article I will explain 4-colour process root cause and print analysis. This is a method I developed over time that will save you critical press time, increase your accuracy and improve your productivity. I will explain 3 things.

1. Tools Needed
2. Critical Print Properties of Process Colour
3. How to do print analysis and quickly determine colour moves.

Tools Needed: In 4-colour process screen print analysis there are many tools and software that will eliminate subjective opinion and guessing about colour moves. Your eyes are not the best choice when it comes to analyzing a print. Just because a print is too red or too blue doesn't mean the solid density is wrong. The instruments I will use in this teaching will be a good colourbar, a densitometer, a hand-held spectrophotometer and some data capture software (DCS3) that speeds up the analysis. However, all the values I show can be measured without software by just a standard densitometer or a hand-held spectrophotometer.

Screen PrintColour Bar: (Figure 1)

This powerful screen print colour bar shown in Figure 1is the IDEAlliance12647-5 Screen Print Colour Bar. This simple control strip contains everything you need to do very sophisticated print analysis but it is simple enough not to be confusing. It contains, pure tonal values of the 5%, 10%, 25%, 50%, 75%, 90% and all the 100% CMYK solids. It reports grey balance of the 10%, 25%, 50%, 75%, 90% as well as the 100x3. (The 100x3 is the solid C,M,Y overprint ink set grey balance.) It has a white patch for the substrate and the Red, Green and Blue overprints.

This is all you need for print analysis. This simple but powerful colour bar can also be used in digital print evaluation. Your analysis doesn't have to be from this colour bar but if you want to use it you can download it for free from our website www.nazdarconsulting.com not to be functions you can also calculate grey balance and solid ink balance.

Densitometer (Figure 2) The Xrite 508:

This is the most basic instrument required to do print analysis. The two primary functions I will use in my analysis are density and dot area. But with these two functions you can also calculate grey balance and solid ink balance.

Density: The most basis data a densitometer captures is density. You can subtract the paper value automatically by using the minus paper feature but I recommend using the densitometer in the “absolute mode” and evaluating density with paper included because the final result you see in an image has paper included.

Dot Area / Dot Gain / TVI: All of these terms represent the value of the area that is covered by a dot compared to the nominal value of patch on the file.Paper is subtracted by simply reading the paper and the densitometer automatically knows this is the “zero” point. Therefore to read dot area, dot gain or TVI, you must establish you substrate as “zero” and your solid C,M,Y,K colours as 100%. The densitometer then just reports the value of your colour bar patch compared to the substrate and solid. A colour bar is the only way that you can be sure you are measuring the tonal value you want to control. Dot area, dot gain or TVI are the numbers representing the tonal value of the printed patch.The difference in dot area from dot gain or TVI is that in dot area the densitometer does not subtract the value of the colour patch. An 18% gain reading on a 50% colour patch in dot area will simply be 68% dot area, but in dot gain or TVI it would be 18% gain or 18% Tonal value increase.

Grey Balance: (Figure 3, Grey Balance):

You also can read a process colour gray patch and determine grey balance using absolute density. You can also check it in L*a*b* but absolute density is easier for a pressman to use because they are normally using a densitometer on press, not a spectrophotometer.If the densities of the solids are right and the TVI is correct, the 3-color grey reading will quickly indicate the colour that is high or low. Figure 3 shows the density values of a C,M&Y grey patch almost perfectly balanced. This is the fastest way to analyze a print on press. The tonal value of the file in the midtone grey patch should be C=49.1%, M=40%, Y=40%. But after overprinting the C,M,Y it should produce a balanced absolute density at about C=.58, M=.58, Y=.58 with a .04 maximum spread tolerance. If the substrate is adding a cast, this simply means you should adjust the curve of the offending color to bring it into a neutral compliance.

100x3 Ink Balance: (Figure 4, Solid Ink Balance). The densitometer will also report your balance of your ink set in absolute density. This is critical to good grey balance because if your C,M,Y overprint is not neutral, you are throwing a colour cast into the print throughout the entire image.

Critical Print Properties of Process Colour:
Critical Print Properties for On-Press Analysis are only 3 things that represent a comparison between the
colour target and the print. They are:

1. Absolute Density.
2. Grey Balance Density values.
3. L*a*b* values compared to my target data set.

Print analysis and determining color moves.
On the analysis below I am just using a low costXrite i1. This instrument is handy because the software converts the spectral data that I scan to what ever I need. (Density, TVI or L*a*b*) The software I'm using is called DCS3. We created this for analyzing screen print and digital print results. You can read more about it at www.nazdarconsulting.com. The software is simple, fast and easy to see what is happening on a print.

Order of Analysis:
Your focus on trouble shooting while on press must be speed. We must get the press running as quickly as possible producing an acceptable product. Therefore we need to have an order of evaluation with the most valuable information for trouble shooting first. If I solve the problem with the first thing I look at, I am not going to continue with analysis exercises that do not matter on the specific print I am analyzing. When the job is completed, I will then use the other data for tracking potential curve, density or ink adjustments I may need to do for future jobs. But my goal while on press is to solve the colour issue and then continue printing with the right solutions as quickly as possible. This is the order I suggest looking at a scan of a colour bar.

1. Grey Balance Assessment:

Just one quick measurement of the grey balance results of the IDEAlliance12647-5 Screen Print colour bar and compare it to the desired grey balance in absolute density.
The numbers on the left are the “Target”. The numbers on the right are the print I am comparing to the ideal values on the left.

Notice that the HR (Midtone grey balance) shows a cyan of .73 absolute density. With magenta at .61 and yellow at .59 this is a blue cast. I have to adjust the density of the cyan down or reduce the dot gain. But which one is the correct move? The grey balance is only is an indication of the colour cast and strong and weak colours. But to correct the colour I need to investigate the solid density before I can make that determination. If the solid density is correct, then the dot gain is too high in the cyan. If the solid density is not too high, then it is a dot gain issue. It could be both. If I am looking at just the grey balance I might assume that the density is too high in the cyan but it might the dot gain or the solid density of the cyan could even be too low.

1. Absolute Solid Density Assessment:

Inspection of the solid densities compared to the colour target is very interesting. Notice that the cyan on the job is only .98 and the target is 1.45. But the grey balance shows that the print is way too blue. This proves that printers that see blue and automatically run to the ink room for the base to lower the density on the cyan are making a mistake. The density is already too low. It is the dot gain of the cyan that is the problem. The print is over all weak in density with the cyan being the worst. The grey balance issue is gain, not density.

1. Grey Ramp Tonal values:

The CMY&K Grey Ramp tonal values map a standard line that tonal values should follow to achieve a neutral grey print. A neutral grey print will allow all the colours within the process image to be represented accurately because the press is not adding a colour cast to the image. You can see by the tone value grey ramp here that, just as the grey bar indicated, the cyan is too high in from the SC (3/4 quartertone,75% area and down.) But notice the solid of the cyan. It's somewhere South of New Zealand. Someone has lowered the solid density to try to fix the excessive cyan dot gain. It didn't work. The problem is the dot gain from the .-tone down. The density is actually too low in the cyan. The “K” in the grey tone ramp is not really the pure black tonal percentage in this graph. It is the result of the C,M and Y blending to make a black. So the high cyan is pushing the line up. The pure black is monitored in the pure colour bars. All the colours are a little weak in the solids. But the magenta and yellow are close to correct from the SC (3/4 tone down.) Looking at the tonal values in a gray ramp rather than the pure colours is much more accurate because the inks here are blending together to create the image.

1. Ink Set Balance: (100x3)

At the bottom of the grey balance analysis there is a line that shows the 100x3. The numbers on the right are the print. The numbers on the left are the balanced ideal target for the ink balance. The balance of the C,M,Y is what is important here. The 100x3 reading is the absolute value of the density reading of the 100% CMY overprint. Notice that the cyan is low on the solid. This means the low cyan density is adding a “red” cast to the upper tonal area. A high cyan dot gain and a touch of “red” from the ink cast causes blue cast but above the . tone there is actually a red cast. This may be why the dot gain of the cyan is up because a pressman was attempting to correct the red cast from the ink and the cyan solid density was the real problem. This is a case of someone correcting the wrong thing and causing an unexpected adverse result in another part of a balanced process colour image. This ink set should be balanced and then the tonal values should be adjusted to produce neutral grey.

5. L*a*b* Comparisons(See the L*a*b* Illustration)

The first thing to look at on press after you have at least 15 to 20 cycles of the squeegee and are printing clean dot and the print is in register is “grey balance”. If the print is in grey balance and the print looks good, print it. But if you are struggling to match colour and it is a chronic problem, then take a look at the L*a*b* comparisons of the print properties of your target compared to your print. I will go through them here to show you that they also indicate the same problems we noted with the densitometer but add some insight on the correct corrective action.

Cyan Solid L*a*b* Analysis:
The cyan has already been identified as too low in density and too high in gain. The solid cyan here shows a 13.16 delta E from my target value. The L* on the cyan indicates that most of the problem is being too light. The L* is 9 points higher. A higher value is lighter on the L* axis. We already know it's lighter from the density reading. The low density is also affecting the b*. The –b* should be -50 toward the blue.
It is only -40.62. This is also a density problem. The cyan is weak. The densitometer told us that as well but it didn't tell us how much it was weak.

The Substrate L*a*b* Analysis:
The substrate is a little warm. I don't have to see the substrate to tell you that it will appear as very yellow. It should be -2b* but it is only .75b*. This also is enhancing my weak cyan problem.

Solid Magenta L*a*b* Analysis:
Magenta is a little weak and green cast.

Solid Yellow L*a*b* Analysis:
Yellow is not weak but has a very green cast with and a* at -9.43.

Red, Green and Blue Overprint L*a*b* Analysis:
All these deviations of the solid colours are negatively affecting the red, green and blue. The green is normally the worst overprint if the solids are not correct or if the print sequence has not been calibrated with the 100x3.

Midtone Grey Balance (HR) L*a*b* Analysis:
Now notice the grey balance of the HR (midtone grey). This is the first thing we measured with the densitometer while on press. It is 12.51 delta E out with an -8 delta E on both the a*and b*. The L* indicates it is too dark. With the solids all being weak it tells me the gain is too much too high. The a* is -8.60 too green and the b* is -8.38 too blue. (Mostly caused by the cyan.)

Conclusion of the Root Cause and Print Analysis:
You may have noticed here that in this article I did not show you the print or the colour target. My objective was to demonstrate that you don't really need to see the print to analyze what it looks like in comparison to an accurate, grey balanced colour target or an accurate computer monitor. Without seeing the print you should be able to confidently know that the print has a strong blue cast in photographs and the solid colors like reds, greens and blues are weak. The tones below the 10% area will have a cast toward the yellow substrate. I also can confidently state that the correction here is the following adjustments:

1. Raise the density of the cyan to normal.
2. Raise the density of the magenta and yellow to normal.
3. Balance the 100x3 inks at full the new full density.
4. Lower the dot gain of the cyan.
5. Adjust the tonal curves until the greys are balanced in the 25%, 50% and 75% tonal areas.

If these corrections are made, our print will look very much like an accurate colour target or a properly calibrated computer monitor.

I hope this article helped you with understanding of how to quickly and accurately do print analysis without looking at the print. Of coarse, I am not advocating not looking at the print, but looking at the print is the worst way to evaluate colour moves or press adjustments. I suggest that you first capture the data and evaluate the numbers before you make a knee jerk colour correction move. When the greys are balanced and the tonality is on the line, you will look at the print and see that it looks like your accurate grey balanced colour target.

If you would like to evaluate and test the DCS3 software that I used in this print analysis you may request a free 30 day trial at www.nazdarconsulting.com. Be sure and mention this article when you request the free trial. You will need a PC and an i1 or Xrite 528 in order to use the software.

Future of Textile Printing In Europe & Asia - Michel Caza

Tue, 24 Apr 2012 21:30:42 +0530

THE FUTURE OF TEXTILE PRINTING (IN EUROPE AND ASIA)
Summary of presentation made by Michel Caza in PRAGUE on 21 March 2012

Place and importance in screen & digital printing technology

- I have been fully involved, since a few years, in a lot of audits in textile manufacturing and printing companies in Tunisia, Morocco, India, Thailand, China, France and Turkey… 50 companies audited from the quality, technical, environmental and social angles.

- Both integrated department in factories and independent screen-printers.

- I was as well in “relatively” small companies as in HUGE companies of which the size seems purely unbelievable in Europe and even in USA !

- The biggest, Shenzhou in Ningbo – China – 28,000 employees, 200,000 m2, a staff of 1,600 peoples on 20,000m2 for the screen printing department only !!. 26 automatic carrousels, 4 kilometres of “long tables” ! They print 350,000 pieces per day ! Can you believe it!

- Mills in Tirupur – India – from organic cotton fibre to finished garment….

- Some of them start from fibres, others from spinning, others from weaving, others from weaved textile and cut, screen print, put transfers and embroidery, sew and mount… Some simply print but no one – except in sublimation transfer – use digital printing !!

Both family work and huge industrial application

- YES, both. We will see that under another angle when I shall conclude !

- Of course, I visited those giant companies, but also a lot of smaller companies having between 25 and 100 employees, either independent and/or small department in huge plants.

- One thing is clear : garment printing is almost totally screen printed – once again, screen printing is not an industry, but a technology used by many industries and this is valuable for digital printing – textile printing is 30% to 35% of the applications of screen printing. This is more than the 20-25% - the graphic and sign part of applications,- but less than the 40 or 45% of industrial applications (electronic, glass and ceramic, packaging, automotive, toys, etc.).

- Digital seems to take over screen ? That is why most Fairs – this include FESPA’s fairs, but we try to change it – does not reflect what is the real place of the screen printing technology. As too much based on “Visual Communication”, due to the place digital printing took in these “imaging technologies”, the visitors (and the magazines) receives the (false because partial) feeling that digital printing took definitely over screen… But what about all the other applications ?

The actual technology

- The actual technology remains for me a “paradox” : a mix of primitive and hi-tech tools and habits !

- You have companies with a lot of sophisticated carrousels, even with CTS, image setter, etc. and on the other hand manual printing with un-sharp squeegees and un-tensioned screens…

- From the giant plant to the garage (you know the one the Americans were so keen of : “make one million dollars in your garage “!)

- A mix also of big investments and simple manual long tables, of both some very cleaver and skilful peoples and others who learned “from the old timers” a lot of bad and even strange habits.

- But, everywhere, I met a desperate need of schools, of training, a huge difficulty to find skilled peoples…. Such a school as DMI in India is the “exceptional exception”, both for graphic, textile and industrial applications of screen printing.

And, at my surprise, I found that the technical mistakes and failures were the same in all the countries !

Quality and Equipment

- I put those two elements together… deliberately !

- You have often the equipment without the skill… Sometimes the skill without the equipments : here, you have the key. No one ALONE is sufficient to reach the quality required and expected by the final customer and end-user.

- I found millions of Euros in investments and… the absolute minimum, the cheapest manual tools, the “ultra-clean”… and the “ultra-dirty”.

- The customer want perfect – and green – products… Produced in a green manner, I will say that again !

- I saw the best equipments and products used in a bad manner… I saw poor equipments combined with good products and also … both bad !

- There are two causes of the too often insufficient quality of the printed products:

- Causes related to screen printing

- Causes related to other factors anterior to direct screen printing or transfers

Screen printing problems

- Lack of sharpness, of definition, of constancy and repetition, lack of adhesion and elasticity or resistance to washing… both for direct screen printing and indirect one – I mean transfers.

- The causes are multiple, from prepress, (even sometimes from the customer’s studio artwork), from the colour of the fabric on the screen, its stretching often totally too low and irregular, lack of good contact when stencilling, damaged lamp, the squeegee blade un-sharp and damaged, the printing strokes repeated several time and sometime in both directions, badly prepared or mixed inks, wrong pigments, strange drying practices, the policy of “immediate profit” ignoring the medium or long term, etc.

- Sometimes one or a few of those mistakes, sometimes the all of them… cumulated !

Other Problems (softness, washing resistance, extension, problems due to the dyes and additives, hard water)

- I could also realize – and correct – many other problems that could be sometimes attributed WRONGLY to the screen printers such as the ones mentioned above : lack of adhesion or/and suppleness, migration in a clear screen printed colour (white for example), lack of softness of the fabric, etc.

- I found several problems related to the use of “cheap” pigments in the dyes – especially colours containing magenta and yellow pigment. It is clear that those pigments, to be resistant to the solar light and other chemical and mechanical constraints, then to migration before or after washing, must be of high quality (7/8 to the solar light), then more expensive.

- Other danger : softeners in organic cotton (which is naturally a little “rough to the touch”), and any additive – often added when dyeing – such as the ones against static electricity, anti-microbial: if they contain the smallest trace of silicones, then you will have problems of adhesion after washing and of breaking of the screen inks ! Then, tests – simple or more complicated - and accurate analysis in labs must be done before printing, if you have the smallest doubt about the dyed textile and even the white fabric.

- Hard water can also be a problem ! In dyeing, in washing after dyeing, when developing and reclaiming the screens, when preparing the water based inks ! The (even micrometric) calcareous stones can prevent a good adhesion and a good cohesion of inks or transfers, then bring a lack of resistance and elasticity of the print.

What to improve? A lot of things !

I wrote a small very precise manual about what its printers, direct or indirect must do & not do!

Fifteen main points:
1. Have good films, sharp and with good edge definition
1. No wooden or iron frames : aluminum or self-stretching frames

3. Choose yellow fabric instead of white for any fine and accurate printed logo or image
1. Use the high or very high tensions – above 25 N/cm anyway

5. Have a light integrator on your exposing unit (metal halide lamp lateral or from the top, but NOT under – no UV tubes). Clean the lamp each two weeks.
6. Sharpen the squeegee blades
7. Have a better control of colours and densities
The respect of the seven above points is the minimum for quality
8. Don’t put the water based inks and the plastisols in the same storage room
9. Don’t use a spray for adhesive : use brush or even screen print it
10. Kiss printing and one stroke only (I saw up to 5 ! Ridiculous) – choose better the fabric, ink and shore hardness!. If two strokes are necessary, flash in between each.
11. Use rather automatic carrousel than the “long table” and manual printing.
12. Flash or/and cure correctly the inks
13. For high densities and some special effect, don’t use multi direct coating, use thick capillary films
14. After printing, keep only a minimum of screens for reprint : reclaim and reuse !
15. Treat the spoiled rejected water

The Future The pressure increases from the buyers and end users.

Environmental & health constraints

- The direct customers and the end-users put a higher and higher pressure : they want more and more green products produced in a green manner.

- The big producers of sport-wears and other garment -here I can name Adidas, Nike, Decathlon, Puma, Quick-Silver - it's of “public and recognized notoriety" refuse absolutely the use of plastisols with phthalates, the use of formaldehyde, (replaced by thiourea dioxide - which I am not sure it is so “clean” !). Some refuse the use of PVC. They refuse the work of children, even in India or Bangladesh, they want that the local social rules be respected, they want that the rejected spoiled water will be retreated, cleaned and reused as much as possible – this position is more and more followed now by most of Cities, States, Countries in the whole world.

- Those companies want also that their “Directive for the Use of Chemicals” be strictly respected and controls are regularly made.

- The use of the products dangerous for the health of the employees, here I mean the use of spray for adhesive the pallets or tables, the use of flock, is strictly controlled.

Improvements in printing quality
- That’s a tendency – now a “must” - which I can better understand than anyone : there are more than 50 years I plead for the quality of screen printed images and marks. I saw so many bad prints and also so many rejects because the customers require quality and sometimes “high quality” !

- The future for quality printing will be in a strict respect of the seven first points of the 15 I mentioned just before.

- For the customers, they must send open files in PDF and not forget to attach the fonts used for the artwork and they must control on the proofs sent that the prints are exactly similar and correspond to what was expected.

Sophistication of images
- As you know, the manufacturers of sport-wears want now to decorate their garments with more than a simple logo or text, but add some « graphic images » to make them more “attractive”. Many of them want to use their stores to sell their own “pure fashion” lines and not only “sportswear's”.

- In the actual period of economical difficulties, this is not so evident ! Fashion lines of major companies saw during 2009 - their sales reduce of 25% when their sales of sport-wears and equipment was increasing of 7% !

- My conclusion, as a joke, "unemployed peoples have more time to do sport !”

Process colours or indexed colours?

- In this growth of sophisticated images, the « photographic images » are actually « in ».

- The problem I saw during my audits is that only a few printers are able to print correct and fine 4 or 6 colours process images, on one hand because of the “general” problems seen above, on the other hand because they don’t know much about the colour profiles, dot gains or loss, densities corrections and compensation, dots size or shape, etc.

- And they often, as they are obliged to use water based colour by their customers, have problems of drying of the small dots in the screen fabric.

- Some of them, as they have sophisticated multi-heads carrousels, think that printing “indexed colours” is a better solution – true or not :

- Easier to print ? Yes: square dots juxtaposed as bitmap objects. Colour separation ? Often extremely difficult if you don’t have a highly skilled prepress operator knowing very well both colours and Photoshop!

- I remember a discussion I had with one of the best textile printers in the world and he said : “We discovered, two years ago that we became “slaves” of those indexed colours ! The “facility” to have 14, 18 colour press was making easy to use 10 or much more colours if not sufficient !... The speed of the press did not change of course but more films, more files work in CTS, more screens, more and longer setting are needed…!. We came back to 4 colours process images for photos reproduction… And we save a lot of money with an increased productivity”.

- This is my feeling too of course ! Process printing is a big future in screen and digital textile printing.

Do not leave money behind on the table - Mike Young

Mon, 23 Apr 2012 21:53:41 +0530

Thinking outside the box!

During the first part of this article series (Jan-Mar 2012 edition of Grafica News), we talked about thinking outside the box at the lucrative new profitable business niche of printing value-added special effects, as an excellent opportunity to shore up one's printing operation because the rules of the game have changed somewhat as the traditional slice of the proverbial pie seemingly shrinks in size. For growth, business clearly favors forward- thinking printers who can deliver mind boggling spectacular results, which can in turn help their customers' businesses to flourish.

As such, we shall continue our discussion by first stating with full conviction why you should not leave any money behind on the customer's table if your company is seeking growth in it's printing operation. For those wanting to improve upon their business status quo performance, by venturing into the wonderful world of breathtaking special effects, we shall outline some of the vibrant and dynamic surface characteristics that can be created.

Leave no money behind on the table!
Many entrepreneurial-driven printing businesses that specialize in industrial applications are beginning to recognize this new but extremely lucrative profitable market niche, which can rapidly fill the voids by literally increasing the size of the pie, through printing 'value-added' special effects that virtually guarantees a windfall in additional business. The type of special effects printing referred to are those created mostly by a single pass of specially formulated UV curable clear ink coating that aesthetically provides an abundance of different effects according to desired needs. Value-added finishing enhancements for commercial printing have gained a huge following in the past two to three years, which has radically reshaped companies' bottom-lines that participates in the specialty. Many entrepreneurs have ingeniously gone further by starting up new enterprises just to handle special effects.

Both commercial and industrial product designers are becoming more demanding; wanting more, better, quicker and for less! Nonetheless, they are also clamoring to provide excitement by buttressing their own products in order to attract more customers-somewhat totally different and imposing—something very special, sensuous and stunning. Regardless of what is screen printed, most print buyers would be more than willing to spend extra for something that visually sets their print or application apart, especially if it boasts stimulating effects which can impressively bring to the table and then some.

Printing companies doubting the lucrative nature of providing value-add features that print buyers are openly clamoring for, to expand their printing business portfolio and bottom line foundation, will find themselves swimming against the alligators. Simply put, by not stepping into this rewarding market means they will be leaving money behind on their customers' table!

This is a dreadful mistake in any business venture because competitors will step right up to the plate and take away with little effort what's left behind on the table! Just if that was not enough, customers tend to gravitate towards suppliers that provide superior effective eye-catching print solutions for their needs, and then usually stay with them as a strong partner as part of their business plans.

Just as if the commercial and graphic art market was not enough for outstanding special effects, at the Printed Electronic Membrane Switch Symposium, held in San Jose, California last summer, an exceptionally high level of interest were enthusiastically shown where such features could substantially enhance and excite many industrial applications too. An array of products creatively printed would standout with greater prominence simply by adding visually pleasing treatments to enhance the often stale-looking mechanical appearance of many printed applications.

Even more impressive from the industrial standpoint of plain-looking prints/graphics are the dazzling results obtained with combination layers, thereby visually creating an inexpensive assortment of exclusive-looking finishes, such as foil stamping, holographic patterns, embossing, 3D doming and even Braille—in which the same processing technique can be used further for decorative purposes. This alone should be of great interest to the Indian printing community due to the vast amount of international industrial/electronic printing now taking place domestically and rapidly growing. The resulting features and characteristics of these ink coatings can potentially replace foil-stamping, doming, silvering and micro-embossing that in many instances are extremely slow in-house processes and routinely very costly to execute. Furthermore, a wide range of illusionary attention-grabbing 3D labels are taking special effect features to another dimensional plateau, while hypnotic 4D dome labels aesthetically reflect stunning imagination of space, haptic-friendly motion and depth under any printed domed logos/labels.

Getting down to business
Let no one make a mistake about it, India is a huge and fast growing marketplace for all things screen printed, be it posters, displays, calendars, greeting cards, advertisements, games, toys, garment tags, consumers packaging (clothing, saris, cosmetics, jewelry, confectionary, gifts, etc), catalogues, folders, leaflets, clothing labels, stationary, gift wraps, bags, wedding cards, cosmetics, etc. The list continuous with countless facets within the industrial & electronic printing sector too; such as membranes/graphic overlays, touch-screens, product ID labels, doming, EL (electroluminescent), nameplates, panels, instrumentation, dials/gauges, IMD, PV/solar wafers, nano-particles, flat glass, circuitry, etc.

Why is UV special effects different and strikingly standouts more than other coatings?
There are many types of ink coatings available to provide certain properties or functionality to a given print or printed product. With special effect UV inks, however, the underlying difference is that they are applied strictly as a finishing enhancement over existing printed matter; to provide surface treatment likeness by simulating certain characteristics or features to parts of the print to improve its overall aesthetics appeal. For instance, take a finished print of an impressive brick/concrete building, if to be accentuated, can be treated with a special effect textured finish just to those parts of the printed surface, which will then make the building look and feel like the real thing to the touch. Similar treatments can be given also to wooded furniture being advertised, to draw attention to the rich wood grain by simulating a real-looking three-dimensional sense to it. In short, special effects provide an enriched depth of legitimacy to realism, a unique visionary real-life view and feel of an otherwise flat plain-looking two-dimensional print left untreated.

Setting the ingenuity plateau to an all-time high, however, these coatings belong to an innovated family product range of clear UV inks, which are formulated specifically for special effects and available in eighteen distinct finishes¯and counting. Manufactured unlike regular UV inks, each coating is developed to yield the exact same exquisite finishing characteristics regardless of printing equipment or curing equipment used.

They are also equally designed to perform explicitly to generate the desired finish right out of the can without measuring or special mixing except for customization with additives. Each gives an extraordinary pleasurable sense of feel, touch, three-dimensional appearance and opulence in richness, selective transformation from deep high gloss to deep matte, distinctive highlights, selective foil, micro embossing and countless other finishing characteristics. Virtually any type of special effects could be created to provide distinctive and stunning additions to actively bring any plain-looking flat print alive.

What special effects are possible?
This superb technique of delivering endless spectacular special effects, simply through creative printmanship, either by single or in multiple layers, has never been easier to fashion something remarkably astonishing out of the ordinary. In addition to those illustrated in Part 1 of this article, below are but a few of the author's favorites even though there are many other striking ones not mentioned herein:
- provides a wet high glossy/superb spot lamination-look selectively to an existing solid matte surface to highlight subject matter

- reversal of the above; selectively print a solid deep matte to an existing glossy surface to accentuate parts of the print to provide a sense of in-depth richness

- provides a dazzling light glistening transparency finish for a variety of different startling effects such as sensational water droplets or sparkling awareness with glitter flakes¯a great transition by adding a touch of reality to precious jewelry
creations

- highly visible laminating effect radiates when printed over silver, gold or virtually any colour, used to create tactile characteristics, Braille printing, dooming and much more

- distinctively create unlimited super 3D holographic or dazzling micro-embossing effects for any occasion, thereby making foil-like surfaces child's play together with over 1,500 vector patterns or custom images to chose from

- spectacular textured simulations can be perfected unlike any other; simply applied to develop breathtaking realistic soft-like surface consistencies such as leather-feel finishing—extremely effective for advertising leather goods and other up-market luxury advertising aids

- eye-catching softening effects are possible that de-emphasizes backgrounds with suede-like characteristic fee and looks

- creating superb relief effects has never been easier¯a great way to add three dimensional effects as well as thick film deposits to small round objects such as berries, pebbles, etc

- another coating provides deep bubble effects to accentuate pimple-/dimple-like surfaces such as the centre stigma of flowers that helps to bring out its sheer natural beauty to the eye

- various degrees of abrasive surface roughness provides great looking realistic characteristics to visually gain that rough feel-like surface look that are not meant to be smooth to the touch, such as to emphasize a crab shell, or simulating brick, sand, concrete, anti-slip appearances, road surface

- silver or golden abrasive offering a beautiful touch of elegance to an autumn leaf, appliances surfaces or high-end furniture applications

- sparkling sheens with deep lustre can be produced to accentuate the body of an automobile for example, appliance, machinery or any decorated panel surface to confer an elegantly appointed ultra-sleek finishing touch not possible by other means

The fact of the matter is the whole screen printing industry is still very much at the tip of the iceberg as it relates to its maturity with special effects finishing. As one continuously marvels at what can be achieved with just a little imagination—the reality is printing operations are creating some of the most innovative and novel finishes conceivably imagined. In time no doubt, special effects will enjoy its own separate category in various printing exhibition/expos printing Awards, such as Screen Print India, America's SGIA, China's CSGIA, Europe's FESPA, etc.

Can these special effects be screen printed by anyone?
Any printing operation having UV screen printing capabilities can start to reap the lucrative rewards of creating special effects for their own customers as well as acting as trade suppliers (contractors) to other printing companies with no in-house capabilities. As a big plus factor for non-screen printing companies, one does not even have to make screens in-house but outsource them instead. However, consider that this type of work is largely regarded as 'finishing' prior to guillotining (since the print is finished but without the special effects treatment), there is an unwritten expectation that turnaround has to be realistically quick particularly with trade printers due to additional shipping times, which are seldom allowed for. During the past two years alone in India, a large number of digital printers have also invested for the first time in screen printing (talk about a reversal knocking the trend!), effectively joining the exclusive club? in order to just provide their own customers with these exciting finishing effects that no other process can successfully give.

Whilst digital printers embrace screenable special effects they are somewhat in a different position in.house capability-wise, as opposed to their offset cousins, insomuch that they principally specialize in providing one-offs to short runs/on.the-fly type of printing, not readily lending itself to handle in-house the capability of added-value special features. Interestingly enough, despite the market growth for special effects it is still very much in its infancy, the DMI printing institute of Mumbai—one of the world's leading training establishments, enrolls up to 60 printers of all stripes at any onetime so participants can learn the art of printing these incredible-looking effects.

Coming up in Part 3
We now have some ideas of the strength and alluring pull-power of this new lucrative market niche of giving value-added treatments to a finish print. We further know what the possibilities are for special effects and how they can radiate any plain-looking print simply by transforming them into an array of eye-catching dazzling finishes. Finally but not least in the article series, we shall explore the types of printing equipment and automation levels to make the venture a truly successful one that will ensure you get the biggest bang for the buck!

How to use process color bar in screen printing - Mike Ruff

Mon, 9 Jan 2012 22:06:12 +0530

One of the most important principles in becoming a high quality and profitable 4-colour process screen printers is learning understand and use a standard 4-colour process colour bar that is sometimes referred to as a “control wedge”. (Figure 1, IDEAlliance 12647-5 Screen Print Control Wedge).

It is vitally important to understand the patch set of the colour bar because attempting to print a process colour image with no colour bar is like a pilot flying in the clouds with no instruments to guide the plane. You have no consistent point of measurement that ensures the print will accurately simulate the file or an accurate proof.

There are 6 critical elements required on a good quality screen print colour bar.
A. A 100x3 patch.
B. Solid Colours of the cyan, magenta, yellow and black.
C. Tonal values at strategic intervals throughout the tonal range of each color.
D. Grey Balance patches for highlight, quarter-tones, midtones, threequarter-tones and shadows.
E. A substrate patch.
F. RGB patches.

In this article, I will explain the patch sets and the purpose of the patch sets of a standard screen print 4-colour process colour bar and how to use it in calibration and in press control.

A. 100x3 Patch

This patch is Cyan, Magenta and Yellow overprinting at 100% of each colour. The result will be a 3-colour black. A balanced ink set measured with a densitometer will be very close the same density on all three colours. (Figure 2, Balanced Process Colour Inks)

For example when you read the 100x3 patch you will see Cyan, Magenta and Yellow reading between 1.35 and 1.45 absolute density. Try to get the numbers within 2 or 3 points of each other. Balanced values are most important. If you are using a spectrophotometer get your a* and b* values close to zero. The L* will be about L*25. This means that as the colours overprint throughout the tonal ranges, they will not be throwing a cast into your image. The sequence you print in needs to be tested before you begin calibration to determine the correct sequence. Then adjust the densities to achieve neutral. Once this is done. Record the sequence and record the densities. After this is completed you are ready to adjust your tonal percentages. NOTE: Normally we find that screen print inks require magenta to be printed first, then cyan, then yellow. Test your inks to see what produces a balanced C,M,Y, 100x3 before you begin other calibration or you will need to go back and do this. If you go back and adjust your ink, then you have to re-calibrate tonal values, solids and gray balance. So start with balanced inks printed in the correct sequence.

B. Solid Colour Patches:
Solid Colour Patches are the most command point of measurement in process colour production. Any printer with a densitometer uses these to measure and control the density of the ink. But a common mistake is using density to control colour. Solid density should be used to control “repeatability”. Once density values are determined through calibration of the 100x3. Density should be constant and something that does not move. The reason this principle is not normally followed in screen printing is because the calibration of the solid densities were ever done correctly to start with.

Also, the solid patches provide a point of measurement you can use to get your densities close to ISO Standards before you make final adjustments in the 100x3 procedure. A spectrophotometer like an i1 rather than a densitometer is used to read the patches and make the initial adjustments. Density is a tool that should be understood as a “repeatability” control. L*a*b* will compare your actual ink colour to the target and allow you to calibrate so you will not need to change densities in most cases once 100x3 and solids are set.

C. Tonal Range Patches
This is the most important point of calibration for 4-Colour Process printing. Not that the solid colours are unimportant but solids can be spot on and the print will be a poor reproduction if you don’t get these values correct. The correct values are the standard tonal percentages of the target you are attempting to match. (Figure 3 Typical Standard TVI or Dot Gain)

In figure three you see some nominal values on the red line that will produce a nice looking print. This is a starting point and it is where a lot of printers stop. Printers will then begin to adjust densities for hours and finally accept a low quality compromise to what they really want. So, get these tonal values correct, but you are not finished at this point. You still need to gray balance throughout the tonal range.

D. Grey Balance Patches
One the screen print colour bar your will see patches marked H, HC, HR, SC, S. These are named differently from the common 10%, 25%, 50%, 75%, and 90% to eliminate the potential of a printer thinking that this is the values they are supposed to be on the film. They are not. They just represent the nominal gray values for each primary tonal area. In each patch, the colors are mixed based on ISO nominal values very similar to what you see in PhotoShop or other graphic art creation software. (Figure 4 ISO Nominal Grey Balance CMY Mixes).

This is just a starting point of gray balance assuming you are printing on standard white substrate, with standard TVI and with standard ink colors, and with standard transparency. (In screen printing we rarely print on white substrate.) But don’t worry about this. This is just a suggested starting point of reference.

The way these patches are used is once the solids are set and balanced, we print the colour bar and measure the grey patches. The percentage of the colors are then adjusted up or down in the tonal values to neutralize the substrate and create an image that has no color cast from the inks or the substrate. This is the most accurate output you can produce and your image will look very similar to a gray balanced colour target or an image on a correctly calibrated monitor. You can learn this methodology through being trained as a G7 Professional or following purchasing and following the ISO TS/10128 Graphic technology — Methods of adjustment of the colour reproduction of a printing system to match a set of characterization data. I highly recommend hiring a G7 consultant to train you in the process. It will be a very good investment and will ensure you are doing the calibration correctly.

E. Substrate patch
The reason you should use a blank substrate patch on a professional 4-colour process colour bar is that if you use a handheld scanner to scan the colour bar like I do, then the software automatically identifies what colour the substrate is without the potential of making a mistake. The software also will calculate how much colour the substrate has in it and suggest a tonal range correction to neutralize the colour cast. (Figure 5, Colour Cast of the Substrate) If you do not adjust the tonal values based on the colour of your substrate you will rarely produce a similar appearance to what you see on an accurate monitor.

F. RGB patches
The Red, Green and Blue patches represent the two-colour overprint results. Cyan over magenta is blue, yellow over magenta is red and yellow over cyan is green. The colours we are theoretically supposed to achieve based on all graphics creation software will not be achieved using curves only. Normally the result is acceptable but really not accurate because the process colour simulation of RGB in PhotoShop and other graphic design software by default is simulating offset inks that are not as pure and transparent as our inks in screen printing. In most cases it is not critical to get the solid two-colour spot colours spot on because most of the time in process colour images you are not going to be printing a lot of solid 2-colour areas. If you are, then colour management on top of the grey balanced curves will bring the RGB in nicely. (But that’s a different article.)

Conclusion:
Be aware that the most important thing in using a professional international standard colour bar in process image printing is to first balance your inks then set your sequence and densities based on grey balance. After that, correct your tonal values to neutral and then diligently scan and record the results. By understanding the standard screen print colour bar and measuring your print and your target you then will be able to make small tonal corrections until you have your process accurate and repeatable.

Achieve 511 Solid Colors in just 9 impressions - Michel Caza

Mon, 9 Jan 2012 21:22:37 +0530

This is an innovation I created during 1963, almost 50 years ago, when it was still difficult for many screen printers to print correctly four colors process halftones…

Here under, a small part of the book (then CD) I wrote at that moment!

“PRINCIPLES AND MATHEMATICAL POSSIBILITIES OF THE SUPERPOSITIONS OF TRANSPARENT COLORS”, By Michel Caza”

Based on the principle of the geometrical progression, the number of possible tints to obtain becomes very quickly huge.

The principle is that each time a color is added to another one, the number of tints that are obtained is doubled and a new one is added, the additional color itself.

For example:

The variety of tints becomes rapidly fantastic; I have pushed, for certain applications in the «optic» art during the seventies, these possibilities up to 15 overprinted colors and I was able to obtain that way... 32,766 tints !

Of course, some of them are, at least to the naked eye, extremely similar from one to the other because of the slight opacifing brought by the pigments, even the most transparent ones; only the spectro-densitometer can read the very little difference, because its possibilities of colorimetric measuring are superior to the possibilities offered by the human eye.

And I need to add that the colors are printed in only one order, by varying this order, precisely because of this very relative opacity of the pigments, it would have been possible to obtain other shades with the same basic colors!

In practice, a color chart with 6 basic colors (63 possible shades) is sufficient to help in resolving many «advertising» problems and a 9 basic colors (511 tints) offers many possibilities in fine art edition.

The above jointed chart and image was printed during … 1964 !!

If I chose the primary colors - CMY - this is for the very simple physical reason that they are the complementary colors of the ones – RGB – of the white light.
With this choice, you can be sure that you always be in harmony in any disposition or juxtaposition of those colors.

Of course you can choose other « basic colors » - transparent of course – as I did for some artists willing to have their « own chart » with colors they where familiar with. But these colors are often more delicate to combine.

The advice of the guru ? : all this is simple in principle, but for sure, it is better to learn the manner to build a chart with the technical help from DMI and Bhargav, despite all this exists in my CD, “The Techniques of Screen Printing” since many years.

Michel Caza

21st Century Color Matcher-Bruce Ridge-Nazdar Consulting

Wed, 28 Sep 2011 20:41:35 +0530

If you’re in the business of selling color images, you want to take advantage of everything you can to make those images the best they can be with the tools you have available. This is why today’s graphic imaging company needs a digital color manager.

A subtle shift in our industry has occurred without most of us realizing it. The shift is the change in how a printing company manages color in their facility. This job was traditionally centered in the ink room, then slowly moved into the prepress department, and now it is making its way to the IT department — and is creating a new industry position I like to refer to as the “21st century color matcher.”

This change is very evident at most graphic screen printing and all inkjet printing facilities. It all started when the trend in graphic images moved toward more process color printing. There is a diminishing need out there for black and white or simple two-color graphic images.

This is a trend that has prevailed in all the commercial printing processes. This trend alone has moved the art and technology of color control into the prepress department, where software allows prepress experts to manipulate and control the color images we print electronically. In this printing scenario, we want the ink on press to be a constant. The goal for the ideal press is a press that is loaded with an ink that prints the same way every time. It is not desirable for someone to be tinkering with the ink once it goes to press to manipulate the color of the image. Most screen printers now see the value of this method, whereas all inkjet printers think this way since changing the ink in the machine is a time-consuming process.

This is where the progress is ending and there is no evidence that printers are prepared to move to what I believe will be the next level of color control. That is the level where color is controlled by the IT department, or more ideally, to persons with prepress, color theory and IT skills. It is the new and changing software products that are the driving force behind color control in the printing processes.

Questions for your company to consider:

- Are you ready to adapt to this next step?
- Do you have the talent on staff to do this work?
- Are you really willing to dedicate the time to get your people trained?
- Do you know where to go to find someone to fill these positions in your company?

The Color Matchers

For many generations, the color in a printing facility was controlled by the color matcher. This person was the heart beat of a printing company. They were craftsmen and their craft was usually learned by osmosis. There was no formal education program for this position; it was a “learn by doing” program that usually took up to 10 years to get really good at doing. These color matchers usually served as the color judge and jury. They could stop the press and production to adjust or change the color of the inks. Theywere the one-man QC Department, an ink and chemical expert — and in many cases — the ink estimator and purchasing agent for a company.

What these traditional color matchers would rely on was their ability to match any color by eye. They would sometimes use a scale to document a formula or to measure out additives to a special ink mix. Ink inventory was managed by memory or written on three-inch by five-inch index cards and stored in a card file replicating a wacky Pantone version of the Dewey Decimal System.

Some of these color matchers moved into the world of instrumentation and a higher-level color control using formulation software. These few innovative color matchers learned to incorporate spectrophotometers to measure colors and feed that data into software that would generate color formulas. These formulation software programs were expensive and took time to learn; however, once set up they would generate accurate ink formulas and determine exact quantities of ink to mix for a specific job. Even more impressive is that they could help the color matcher work off inventories of previously matched inks that were left on the shelf from prior jobs. Many of these color formulation systems, along with training, were provided to printers by their ink suppliers.

During this same time, digital image creation became the primary method of generating art work for printing. This facilitates the growth of full-color printing, which eventually leads to the reduction of spot color printing and color matching. This change affected all of the printing processes and the prepress functions, so the different printing processes start to look very similar. Color is now being controlled in the art and prepress department.

Process color becomes the dominant color reproduction method for graphic screen printing and is the dominate-method of color reproduction for wide-format inkjet printing.

There also are trends in the commercial printing world that are driving change in all of the print processes. These trends have been documented by SGIA and PIA/GATF for more than 10 years and are part of the reason that digital printing is the only growing printing process because they all favor some of the inherent characteristics of digital printing. These printing trends include:

- An increased use of process color
- Requirement for faster turnaround
- An increased requirement for fulfillment services
- Multiplatform printing companies
- Digital printing intrusion in most markets

These same forecasts list “digitalography” as the up and coming printing process. This is a broad term that encompasses many different digital printing processes. They also predict that inkjet will eventually become the dominant digital printing processes. This is good news for wide format inkjet printers as well as suppliers to this segment of digitalography.

Digital color is color that is created, manipulated, and sent through a digital workflow of software and then finally printed by any of the commercial printing lithography or inkjet. This is specific color that has been translated into numbers (L*a*b*) manipulated with software, then translated back to color. This ‘new’ type of color matching requires a completely different understanding of color — its color by the numbers. Understanding the math is as important as being able to see subtle differences in two red patches.

Today’s color matcher needs to understand how these numbers are captured with an instrument, how software compares these numbers, and how the software manipulates the numbers in order to translate those numbers back into a color. This is the work of the 21st century color matcher.

The 21st century color matcher (CCM) does not mix ink, are not a chemical expert and most importantly, they do all they can to keep the press running. Instead of stopping the press to correct today’s color, the 21st CCM would collect data from today’s press run to make improvements for tomorrow’s press runs. Their responsibilities are greater because the overall influence on the company is greater. In order to meet today’s shorter deadlines on more complex color jobs, the stakes are much higher to deliver the right color in as few prints as possible.

The 21st CCM could also be called the digital color manager. This is a full-time job for larger companies, although few companies realize it. The prepress manager on a part-time basis currently attempts the work; and therefore, the work either never gets done or is done only half way. The most common scenario is for a company to own profiling software and hardware while running their day-to-day printing using one profile or configuration. This happens because no one is given the time to create individual media configurations.

If you’re in the business of selling color images, you want to take advantage of everything you can to make those images the best they can be with the tools you have available. This is why today’s graphic imaging company needs a digital color manager (DCM). If you are a smaller company and cannot afford a full-time DCM, then you need to rent one. Just in the same way you would rent payroll services, tax and accounting services, and IT services.

Why is digital color management such a critical position? Color can be controlled and predicted better than ever before; however, controlling it has become more complicated than we are willing to acknowledge. Software is updated every year, computers become more powerful, and new products enter the market every month that can improve workflow and efficiency. Who in your company is taking the time and has the expertise to evaluate which of these products are best for your company? If your resident color expert is constantly focused on production, they are not managing your color — they are trying to get work out the door.

This position of the DCM is critical to your company and there are several sets of skills this person should have. First are personal characteristics. The ideal candidate would possess many of the following qualities:

- Ability to communicate effectively
- Ability to provide training to all levels of knowledge
- Ability to focus on specific problems
- Ability to network to find solutions
- Ability to recognize new ideas
- Ability to multitask and complete tasks in an organized and systematic fashion
- Ability to know how to document procedures

The technical requirements for the digital color manger are:

- Understands the principles of additive RGB and subtractive color CMYK
- Knows L*a*b* color space, spectrophotometry and densitometery
- Knows how to use rendering intent, color targets and ISO specifications
- Is trained in G7® color control methodology
- Can work with the limitations of the inks and substrates they have
- Has a fundamental understanding of all of the print processes

The IT requirements of the digital color manger are:

- Has a broad knowledge of prepress, business and workflow software programs
- Is a master of the media configuration process and editing
- Knows the curve process for nondigital printing
- Can establish workflow procedures.

In general, many of these skills are not learned through the osmoses process.

These skills are learned through structured training and educational programs. Structured training has not been the primary method of learning for the experts in the screen printing and wide-format inkjet industry. Our industry has relied on getting skilled employees by either hiring someone from another company or by providing on-the-job training so they can learn during production. This may have worked with the traditional color matching person over a five-year period, but it is not effective when trying to develop a DCM with up-to-date expertise.

This position now requires our industry to do something they have not done in the past — hire people who have attended colleges and technical schools with graphic arts programs. Very few of these programs will teach students the specifics they need to know about wide-format and screen prepress and color control. They will deliver a person that has a foundation in prepress art, design, and workflow software as well as knowledge of color theory. This will usually be focused around offset lithography printing; however, the prepress aspects apply to our processes. From that point, you would be responsible for providing information about wide-format imaging and and ensuring they stay upto-date on the process through Webcasts, seminars, trade shows and networking opportunities. This is an investment and it would be smart to protect your investment with a contract.

Benefits from Developing or Hiring a Digital Color Manager

There are many benefits a company can gain from developing or renting a DCM, including:
- A person assigned and given necessary time to improve color, will improve color.
- There are proven products available on the market that save ink, time and to reduce waste if managed by someone.
- New products and processes will keep a company competitive.
- Providing new solutions and processes attracts new customers.
- Smart innovative people like to work with smart innovative people.

In summary, there has been a major change in the way color is controlled in a printing facility. This change has been driven by the printing trends that are a result of what is now possible because of developments in digital printing and in digital prepress color control. This has moved color control out of the printing shop and into the prepress and IT areas, and all of this requires a new type of person to fill the position of the digital color manager. This also requires a new mentality on the part of production-focused management in order to stay competitive in the delivery of cost-effective color images and digital color management. This will be critical to the success of a printing business that is focused on delivering full-color images to their clients.

Spot Color Tolerancing by Mike Ruff - Nazdar Consulting

Wed, 28 Sep 2011 20:14:33 +0530

One of the more productive skills a screen printer can learn is spot color tolerancing using an instrument. What I see most of the time is “visual” tolerancing. Many printers actually believe they can do better visually than they can with a color spectrophotometer. They are wrong.

Two years ago, we did a study of spot color tolerancing at a print company that required very tight color control because they manufactured and printed vinyl fabrics used for upholstery. The company employed a production artist that had extremely good color vision. But the management of the company called us in to evaluate the approval and rejection procedures. This procedure is called color “tolerancing”. You first establish predetermined degrees of deviation and variation from an intended color target. Deviation is “difference from the reference color target”. Variation is “color differences during the print run”. The company needed to make a decision on their color tolerancing guidelines. The challenge for the management of the company was that they had a reject rate of over 65%. They were not making any money. Therefore the critical success factor for the consulting project was to determine if the visual rejections were correct and test color tolerancing by instrumentation to assess if color instrumentation was more accurate and consistent on the same samples. We were then asked to report our findings to management. The experiment we developed featured 5 different color patterns. Two were saturated darker colors, one was a midtone and two were highlight or lighter colors. We had the production artist approve the acceptable samples we used for a reference color. We measured and established our target values. We printed the same patterns every day for 4 days. We then measured the new patterns each day and the production art manager visually accepted or rejected the print results. Our testing revealed that the production artist was very inconsistent. He would reject samples in the morning and then approve the same samples in the afternoon. His rejection rate was very close to the 65% number reported by the management. The color measurement instrument was consistent. We established a dE of 2 for lighter colors and 3 for the midtone and darker colors and we could measure the same targets morning or afternoon and the results were the same. We also measured the same targets one day and then measured them the next day and the results were the same. The reject rate we estimated based on the established allowable deviation and variation was only around 20%. This proved that the production art manager was rejecting acceptable prints and costing the company thousands of dollars each week. Now all tolerancing is done by instruments.

The reason color tolerancing with instruments is so important to screen printers that print spot colors is it changes subjective opinion into objective facts. Human vision can change morning to night, in different lighting conditions and even with caffeine or with no caffeine. An instrument is very consistent. A human’s visual perception is also affected by surrounding colors.

(Figure 1: Chromatic Infusion) The two images shown in this example appear to have two very different orange stripes. They are actually exactly the same color. An instrument would report that the color is the same. A human would reject one of both of them just because of colors that surround the orange. This can cost you time and money as you reprint jobs that are perfectly acceptable.
When a printer learns to communicate color in numeric terms, an art and craft business becomes a manufacturing process. This is where hyper productivity and profitability begins. As our industry struggles to survive, we must move away from an art form and become graphic manufacturers. What I hope to communicate in this article is the basis of color tolerancing by instrumentation, how color decisions can be made through the use of instruments, how to get comfortable with the numbers and how to effectively apply numeric color tolerancing in your screen printing department.

Tolerancing Terminology
There are multiple names for almost all color management elements. This can become confusing. ISO committees are actually addressing this issue now to eliminate some of this confusion. In order to understand tolerancing there are four terms you need to be sure you understand.

- Delta E: (Normally stated as dE) An easy way to remember this is think of the “d” as deviation, most color manuals call this distance from an intended color but I think deviation is easier to understand. The E is the amount of deviation from your intended target.

- Reference: This is your target numbers. The target numbers can be entered into a spectrophotometer by measuring the reference target or manually entered into a spectrophotometer.

- L*a*b*: The third term that is important to understand is L*a*b*. This is the numeric coordinates CIELAB color space. CIELAB color space is device independent. It is the same in North America, Europe, Asia, South America, Africa and every other place in the world. If a color is specified in L*a*b* any person in the world that matches the values and measures them with a high quality calibrated instrument will be visually acceptable to a reference they have never seen. The only color difference could be the limitations of the measuring device.

- Tolerance: This is the “acceptable” difference stated numerically from the reference color to the color you are measuring. What is acceptable to one customer may not be acceptable to another. This is a number that needs to be negotiated based on the reality of actual production limitations.

- Chroma or Saturation: This is a little different than just darkness and lightness. A color can maintain the same L* value (darkness and lightness) yet be different in Chroma or Saturation. Chroma or Saturation is how deep or saturated the color is. For example: Deep red compared to a medium red. It’s the same color… just more saturated.

- Hue: The hue of a color is the family of color it belongs to. For example: Red is a hue, Green is a hue. Yellow is a Hue and Blue is a hue. All the colors in between can shift toward a different hue. A color that moves in hue is actually changing to a different hue.

Understanding tolerancing formulas
The most common and simplest color tolerancing formula is a formula developed when the L*a*b* colorspace was created in 1976. This made it possible to create delta-E 1976 (dE76). dE76 is a spherical distance in all directions that a color might locate in an attempt to match a reference color the distance calculation put the color in our mind as a number. The higher the number, the less accurate the color match. Some people refer to dE76 as plain delta-E. It is also known as DEa*b*, CIE L*a*b* tolerancing, dE-Lab and dEab in ISO Standards. You also see the Greek Letter for delta used rather than “d”. ΔE76 or ΔE76. The formula is pretty simple. (See Figure 2, ΔE76 formula)

For comparing one value to another, it still may be the best formula to use just because of its simplicity. So for an ink manufacturer or a substrate manufacturer it works well. But there is one major problem with dE76. Human vision is not linear. In other words we accept a deviation or variation in chroma or saturation of a color to a greater degree than we accept Hue shift. Human vision is very good at seeing hue shift. For example if a green shifts toward yellow, we see it very quickly. We might not even notice a Chroma shift of the same amount. (Figure 3: dE and visual agreement)

Tolerancing Formulas that address Human vision.
All though ΔE76 provided a huge benefit to the industry, we still have problems with setting tolerance numbers because of the human visual acceptance factor of chroma verses hue shift differences. We can have a ΔE of 3 and like one result and not like another. In other words, we don’t agree with ΔE76 about 25% of the time. That’s one in every four measurements.

CMC Tolerancing
In 1984 the Colour Measurement Committee of the Society of Dyes and Colourists of Great Britain developed CMC for the textiles industry. This was a huge success because the tolerancing shape of an ellipse simulated human vision much closer. (See Figure 4: Elliptical Tolerancing)

This helped tremendously because now a tolerance of ΔE*3 would pass if the deviation was in Chroma but fail if the color is shifting hue. This is simulating how a human would visually reject or accept a color.

Even better formulas.
Even though CMC was very good and is still the preferred tolerancing formula for many graphic producers today. Improvements have been made to this formula. A technical committee of CIE published an equation in 1995 called CIE94. The equation is an elliptical tolerancing formula like CMC but CIE94 was developed for the paint and coatings industry. CIE94 is a common formula included as an optional selection on color instruments like the Xrite 500 series of hand held spectrophotometers. (Figure 6: CIE94 Formula)

The DE94 created ellipse tolerances similar to CMC and the Ellipses are wider in colors that are hard to see hue shifts in. For example Greens. (Figure 5: Farnsworth Munsell 100 Hue Color test) Figure 5 is a Farnsworth Munsell 100 Hue test Color test that I completed. You can see that I have very good color vision no matter what my wife says. (She says I can match my socks. I really can… I just don’t care.) Notice I have trouble with greens. This is not uncommon. The newer formula addressed this.

dE2000
The most accurate to human agreement formula today is dE2000. dE2000 is the first major revision of the dE94 equation. Unlike dE94, which assumes that L* correctly reflects the perceived differences in lightness, dE2000 varies the weighting of L* depending on where in the lightness range the color falls. dE2000 is still under consideration and does not seem to be widely supported in graphics arts applications. This will soon change because ISO will soon be replacing dE1976 with dE2000 for all new graphic arts print color standards and all revised graphic arts color standards in the next few years. This is a very complicated formula that addresses some of the other differences that DE1976, CMC and CIE94 did not. It has been verified to agree and line up with our vision in correct lighting much better. There are five corrections in dE2000 from dE94.

- A hue rotation Term (RT), to deal with the problematic blue region. (hue angles in the neighborhood of 275 degrees)

- Compensation for neutral colors. (the primed values in the L*C*h* regions.

- Compensation for lightness. (SL)

- Compensation for chroma. (SC)

- Compensation for hue. (Sh)

(See Figure 8: dE2000)

Three Important Ingredients of an Affective Instrument Based Color Tolerancing Program
- Knowing what your equipment can maintain in dE.

- Understanding that a dE number is not the same in lighter and darker colors.

- Understanding what a dE numeric difference actually looks like.

Knowing what your equipment can maintain in dE
I got a call from a panicked client early this year. She said their largest account was going to require them to screen print a spot color on an eight foot long sheet of PVC material and maintain a dE of 2. They needed help on how to do it. My first response was it probably can be done but not maintained in production. Therefore the first thing we need to do is determine what the equipment can consistently hold day to day as well as sheet to sheet during a production run. You cannot agree to produce for a client a dE lower than your press can hold. If you do, you will force your printers into two really bad choices, to fail or lie. Both choices are bad for your company. Therefore, before you agree to hold a tolerance number someone has asked you to hold, test the press with the color they requested. Many clients push us into proofing tolerances and not production tolerances. There is a huge difference. Check out ISO 12647-2 the Standards for Offset Litho. You will see that proof tolerances are much lower than print tolerances. Clients hear a number and they think we can just “dial it in”. In the movie Dirty Harry, Client Eastwood told the guy, “A man has to know his limitations.” (Then he shot the guy.) Oh well, it was quick.

Understanding that a dE number is not the same in lighter and darker colors
Human vision will accept a greater color difference in a darker color. Grays, pastels and basically all lighter colors are much easier to see a color shift. The mistake I see many people make is they have a spot color matching tolerance of “one number”. For example it might be a dE of 5. The problem with this is that a dE of 5 will only be a slight color difference in a saturated color but it will be a major visual problem in a light gray or pastel. dE2000 automatically tightens the tolerance in lighter colors but a visual sample should be produced to make a decision on what your tolerance should be.

Understanding what a dE numeric difference actually looks like
Figure 9 is a visual sample created with Nazdar’s CATZper software. (See Figure 9: The Tolerancing Snowflake)

This tolerancing tool, called a snowflake, had an exact match in the center of the snowflake. Then each of the adjacent colors move gradually away in color accuracy 1 or 2 dE on each square. The a* axis is green on the left and red on the right. The b* axis is yellow on the top and blue on the bottom. The darker and lighter colors are not changing hue. The a*and b* are exactly the same on all the colors of the L*. The color is just getting darker and lighter by the addition of black. The a* axis only changes on the a* numbers. The b* is the same on all the colors. The b* axis does the same. While it may look simple, CATZper is a very sophisticated color tolerancing tool. If a screen printer produces one of these snowflakes for an intended reference target he will then have a good visual reference that will lead to understanding what the number should be based on the saturation of a color. The screen printer can also produce these snowflakes and educate a customer that is asking for unrealistic tolerancing. For example a customer may be asking for a dE of 1 in a saturated color when there isn’t a visible difference at 3. Chasing a 1 is just a waste of time if you can not see the difference. You solve this by determining what is visible at the beginning.

Conclusion:
I hope this article has given you some critical knowledge and has inspired you to do some testing with your equipment and color measurement instruments using dE76, CMC, dE94 or dE2000. You will find that when you really understand what a number means, you will be able to make good decisions regarding color tolerancing. Good decisions will produce accurate color quicker and with higher profitability.

Mike Ruff, Chief Technology Officer, Nazdar Consulting Services
Send comments or questions to: mruff@nazdar.com

Importance of quality in stencil making - Dirk Oelschlager

Wed, 28 Sep 2011 19:18:02 +0530

Why quality in stencil making is so important?, Some thoughts by Dirk Oelschläger

There are plenty of important criteria’s to consider in order to do a successful screen print, but the most important point is the fact, that a print can never be better than the original artwork. This explains easily why one should pay much attention on stencil making to keep potential for mistakes as low as possible. Even the smallest mistake in this first link of the process chain will lead to a loss in quality, resolution or edge definition which the customer of the final print would most likely not accept.

And beside the quality aspect, a perfect made stencil last much longer and saves money. Imagine if the stencil would break down before the job has been completed. To make a new stencil is time consuming and the press would have to stop in the meantime. To avoid such a worst-case-scenario, I would like to share some of my suggestions how to create a long lasting stencil in perfect quality.

The first step is always the correct mesh selection. As finer the mesh threads, as higher the maximum resolution which can be achieved. Screen printers often talk about the mesh count for a specific print job but forget the differences of the thread thickness. E.g. a 120-34 mesh could be not suitable for finest halftones as the thread might block the open areas while a 120-31 fabric would solve the problem.

A good stencil maker should also be aware, that yellow mesh provides significant better edge definition vs. white mesh. The reason for this phenomenon is the fact, that white mesh reflex light during the exposure process and leads to undercutting of those areas which shouldn’t be exposed. Yellow mesh prevents from reflection and promotes sharper lines without a “saw-tooth” effect.

Before the emulsion can be coated on a screen, the mesh should be always degreased to avoid coating defects. Multipurpose fabric treatments like Ulano Magic Mesh Prep combining the properties of screen degreaser, wetting agent and antistatic treatment and improving the adhesion of emulsion or capillary films. As a result, the screen will last significant longer.

If the screen is ready to be coated, one should consider all factors which influences the coating thickness (EOM = emulsion over mesh). Keep in mind, the thickness of the stencil is responsible for the ink deposit and therefore very important to be controlled. What would happen if the four stencils which are required for a CMYK print job would variety in thickness? The colour of the print would not match with the original artwork. Manual emulsion coating can be very tricky as there are various coating parameters as speed, pressure, angle, shape of the coating trough etc. which must be controlled. By using an automatic coating machine, all parameters are fixed but the operator often forget to look after a constant filling level of emulsion in the coating trough which have the greatest influence at all to the EOM. A nice and elegant way to make our life easier is certainly the use of capillary films where the coating thickness is controlled by the manufacturer of the film.

If the stencil has been properly dried, it’s ready to be exposed. In my career as a technician who travels worldwide I have often observed that screen makers tend to underexpose stencils. The answer is simple, because it makes their life easier as developing goes faster and resolution of the finest details is always good, but they shift the problems of underexposed stencils to the printers. Why it’s important to pay so much attention on the exposure process? An underexposed stencil will not have sufficient mechanical and chemical (solvents) resistance and might break down during the print run. A step wedge exposure calculator is a very simple but helpful tool to check the optimum exposure time. Ask your Ulano representative to provide you with such a basic utensil. And coming back to yellow mesh, it also provides wider exposure latitude vs. white mesh and minimizes the risk of underexposure.

Stencil making looks very easy and simple but if one goes closer to each processing step it turns out to be more complex. In my point of few, stencil making is the heart of screen printing and plays a very important roll to achieve a good print quality. So next time if you make some screens, pay even more attention to deliver perfect stencil quality to satisfy your customer – the printer.

Why manual screen printing is tougher - Mike Young Part 2

Wed, 28 Sep 2011 18:46:51 +0530

Why Manual Screen Printing Is Tougher Than You Think! Part II
By Mike Young, Imagetek Consulting International, North Haven, Conn., USA

Notes for the editor: Please use suitable photos from your library in addition to the three illustrations supplied (on another file).

In the second and final part of his article series, Mike Young reviews the significant influence and sheer beauty of the floodcoater (also called floodbar and scrapper blade) when comparing semi/fully-automatic printing machines to manual printing for taking full control of print quality and overall production performance.

In Part 1 of this article (Grafica News - April 2011), Mike examined the quantifying needs to make screen printing a mechanical repeatable process, in order to replicate each print commercially acceptable or a fabricated part if industrial, electronic or medical application meets or exceeds specifications. Missing entirely from the manual printing-equation is the all-important floodcoating function under strict and proper uniform control―the underpinning reason why repeatable print results are all but impossible to achieve when manually printed.

Part 1 also mentioned the dangerous vulnerability of the squeegee since it can have some 50 distinct very influential prominent variables―mostly a tool that operators have very little control over. However, if the squeegee was left just do its basic job, that is transferring the ink through the screen, one can then rely on the floodcoater to meter, or gauge, how much ink the squeegee eventually transfers―thereby improving final print quality and repeatable results because the floodcoater’s variables can be controlled in a much better manner than the squeegee’s.

The beauty of the floodcoater.
The floodcoater has one extraordinary advantage over its squeegee cousin. Any adjustments made to it to improve print finish will never affect registration because flooding takes place only between print strokes. Regardless of whether print image or registration is an issue, it is interesting to note that a floodcoater’s length ought to be that of the squeegee to produce a ‘pair’. Together with a smooth unblemished edge, it has at least 19 additional varying components during the flooding cycle―equipment type permitting. In no particular order of importance they are:

Quality grade/hardness: as squeegee material or plastic-like edge strips covering metal floodbars are used alternatively to metal floodcoaters with some equipment and setups while stainless steel holds up better than aluminum.

2 x edge profiles: rounded or sharp, fully in contact with the mesh (Fig. 1)

Face profile shape: various shapes to increase ‘ink roll’ although rarely used

Straightness: linearly straight along its entire length without deviations in height

Camber: creating a slight convex curve to some degree along the entire edge (not to be confused with the above)

2 x angles of attack: 0º and 15-45º from the vertical (Fig. 1)

Mechanically on-press set angle: conflicts with those above

2 x lengths: as a pair with the squeegee or longer (the latter results in a different deposit layer amongst other issues)

2 x pressures: overall floodcoater bridge assembly itself and individual cylinder pressure variation (not to be confused with the following)

Balanced: floodcoater mechanically levelled to screen surface once it is down in the flood position, regardless of pressure force

3 x speeds (depending on setup and equipment type): accelerating / starting, maintained speed and decelerating / stopping within the range of the image area

2 x skewed angles: floodcoater skewed (known as ‘snowplough’) a few degrees in the direction of flooding in either axis

Print / flood or flood / print mode as well as variable dwell time elapsed between each print stroke is not included here since they have been credited to the squeegee stroke.

If adjusting these physical and working components instead of adjusting the squeegee’s to modify the end print result, then the operator is in a greater position to control print appearance much better than at any time previously. Even if these adjustments are deployed as an addition to the squeegee, controlling deposit thickness, uniformity and image definition becomes much easier to consistently achieve and manage.

The role of the floodcoater.
Contrary to belief, the floodcoater’s job is not to push ink back to the beginning to commence the next print stroke! There are some industrial screenprinting machines, especially those for high-tech applications such as small format printed circuits and photovoltaics (for solar panels), that print without the function of flooding.

Its principal purpose for high-level printing performance is to prime the screen with ink. In this instance, the squeegee becomes subservient to the floodcoater. When the squeegee has finished its print stroke the screen is ‘dry’, that is to say no ink is left laying on top although a certain amount will still be inside the screen itself (fabric openings), but not enough to print the next piece properly. Once flooded, the whole screen is primed or recharged with an even layer of ink and how much is left behind depends on other factors as stated below.

The ensuing squeegee will always try to push through what remains on top of the screen, seemingly without any form of control. The squeegee is, after all, a piece of rubber-based blade with some 50 distinct variables all-interacting between themselves. Consequently, the squeegee simply tries its best to transfer whatever is left on top of the screen. So, if for instance there are some small nicks in the floodcoater’s edge, it will correspondingly leave behind streaks of thin lines on the screen which is not difficult to see with overhead reflecting light. When the squeegee prints, these lines will correspondingly transferred to the substrate, thereby possibly resulting in a reject. Some operators even complain that their squeegee sharpener is no good because it still leaves streaks behind in the print, nonetheless, it is quite common to remove the floodcoater only to find nicks along its edge lines up perfectly to those in the finished print.

The flood stroke.
It is important to realize that the flood stroke actually takes place while the screen is suspended in mid-air as opposed to when it is up against the hard print table during the print stroke. The flooding sequence therefore takes place in a less than advantageous setting and one that is very difficult to manage without some creative forethought. If characteristics of finished print can be customized and tweaked without adjustments made to the squeegee―then it is more beneficial to do so. If by adjusting one or two floodcoater’s variables or changing edge profile, to control the precise amount of ink layer left on the screen all the way down to leaving none, must be a good thing to go that route.

This means it is possible to generate a heavier deposit for weak colors or thicker coatings (Fig. 1a), normal deposit for standard jobs, colors and images (Fig. 1b) and perhaps thin to none for fine lines, detail and monotones/4 color process (Fig. 1c). This gives press operators a powerful tool without ensuing registration concerns or other drawbacks, which playing around with the squeegee could otherwise yield. It could be said that the squeegee ought to be used only for printing the ‘image’ (transferring the ink) whilst the floodcoater determines ‘functionality’ (precisely how much will be transferred). This distinction ought to be appreciated particularly when elevating the process to a higher level in print performance.

When using this form of control during the flood cycle, it becomes possible to lay down a heavier deposit, or the reverse, when the mechanics of the screen fabric, image or ink are not favorable for the job. However, if the fabric is too coarse for the job, printing a finer layer of color (shown in Fig. 1c) is easier to achieve, particularly when seeking fine image detail. Only ink deposit thickness is affected and not registration as the case might be if the squeegee were adjusted instead.

Custom use of the floodcoater will also improve image definition and uniformity throughout the print area, without affecting registration or transferability of the squeegee once set. Therefore, the floodcoater could be viewed as being a more powerful tool than the squeegee blade itself to provide quality coating deposit consistently and greater image performance with less hassle.

Manual printing vs. semi-automatics.
When jobs are manually printed on a hand printing table, most which are clamshell in design (that is the screen hinged at the rear) while a few models adopts the parallel lift principle with or without a one-arm squeegee attachment. After the print stroke, the screen is raised a little from the substrate and the operator manipulates the squeegee over the pile of ink and then drags it back to the other side of the print area in some haphazard fashion. As the floodcoater’s principal role should be to prime the screen uniformly over the whole screen the squeegee would simply transfer the same uneven haphazardly deposit layer of ink for sure. Likewise, a mechanical floodcoater would ensure the flooded layer would be smooth and consistently uniform throughout.

As stated, the flooding action determines how much ink the squeegee can potentially print, therefore, unsystematically dragging the ink back with a squeegee in an uncontrollable and irregular manner, all while the screen is airborne, cannot be good for uniform ink deposition despite any form of control with squeegee pressure.

Dynamics involved with uniformity.
In today’s marketplace, to obtain a uniform deposit evenly over the whole area with a blemish-free ink deposit is a huge undertaking―somewhat more difficult than most people realize. When printing onto clear substrates for example, their surfaces are typically so unattractive for the ink it does not want to freely release itself from the screen, so many printing faults have nowhere to hide from the viewer. In order to achieve some kind of ink coating uniformity and consistency, consider the dynamics of deposition.
Despite the squeegee being too long for the job as shown in Figure 2a, the greatest pressure points against the fabric are at the ends of the squeegee blade. This implies that the weakest part must be in the middle where there is no real integrity. To make matters worse, fabric can actually ‘sag’ a little according to screen tension, although the effect is exaggerated in the illustration.

Whilst this phenomenon is not easily seen with an eye, the consequence is enough to demonstrate that there is a lack of pressure in the middle. However, this may not be of any concern because during the print stroke, the screen is linearly in contact equally throughout the squeegee’s length when down in the print position (Fig. 2b). If follows that when using the proper length squeegee blade, printers have better control in obtaining a more uniform deposit layer, as shown in Fig. 2c, because the sagging effect no longer exists (except with extremely weak tensioned screens). Conversely when using a floodcoater that is also too long for the job (Fig. 2d), the sagging effect is very real this time and extremely detrimental to print quality because ink is pushed back only after the screen has separated from the substrate while in midair.

Due to this, a greater amount of ink is left behind in the centre of the screen than at the outer edges, while the correct length squeegee can only duplicate the exact same outcome―by consequently transferring more in the middle (Fig. 2e). This is not an ideal way to achieve uniformity, particularly with any ultra-thin / low solid inks.

Many printers are quite familiar with heavier deposits in the centre (or less at the outer edges) because as it is easily seen with overhead lights reflecting on a flooded screen. However, regardless of how careful an operator manually prints with the squeegee, the end print results will always be irregular with more ink coating transferred in the middle if the floodcoater is too long. With the proper length floodcoater, the sagging effect can be eliminated or significantly reduced (screen tension permitting) to provide a more acceptable print result.

In principle, it is realistic to assume with manual printing that every time the print size is increased, the dynamics of printing, or the degree of difficulty, more than doubles just to maintain the existing level of print integrity―never mind other enhancements sought. While this is also true with semi-automatic printing equipment, many of the technical hitches and complications would have already been absorbed, especially with a mechanically-controlled floodcoater, as well as consistencies related to repeatable quality and performance.

Bottom-line; it is impossible to eliminate the ‘sagging-effect’ in the middle of the screen by manually flooding with a soft squeegee while the screen is suspended. At least with a mechanical metal floodcoater, one has a much better chance of achieving the objective of getting a nice smooth uniform print throughout the image area.

One last word regarding deposit uniformity, the floodcoater’s edge must be perfectly machined flat along its entire length (Fig. 3) otherwise tightly controlled deposition, when needed, will be all but impossible to achieve.

Conclusion
In a practical sense with equipment automation, a little tweaking with the floodcoater is often all that is required rather than continuously adjusting the squeegee and potentially risking having other problems. Depending on how it is used, the floodcoater can be just as important as the squeegee. Controlling how much ink remains flooded on the screen, prior to every print stroke, has a tremendous advantage in favor of the operator. Print personnel should never be afraid to learn its influence, develop its attributes as a powerful tool and use it to its full potential.

Unfortunately, there are so many uncontrollable irregularities and idiosyncrasies involved with manual printing, as oppose to printing with ease with a semi-automatic―largely due to a fully controllable flood action. Regardless of how much one tries to mechanize manual printing, it is still very much an artistic discipline despite the fact that consistency is necessary for profitable jobs regardless of print specialization or marketplace.

Power to the floodcoater!

Possible call-outs to consider:
“Contrary to belief, the floodcoater’s job is not to push ink back to the beginning to commence the next print stroke!”
“.....It could be said that the squeegee ought to be used only for printing the ‘image’ (transferring the ink) whilst the floodcoater determines ‘functionality’ (precisely how much will be transferred).”

“.... the floodcoater could be viewed as being a more powerful tool than the squeegee blade itself to provide quality coating deposit consistently and greater image performance with less hassle.”

“.... the flooding action determines how much ink the squeegee can potentially print....”

“.... it is realistic to assume with manual printing that every time the print size is increased, the dynamics of printing, or the degree of difficulty, more than doubles just to maintain the existing level of print integrity―never mind other enhancements sought.”

Respectfully submitted by Mike young
Imagetek Consulting International, August 13, 2011

Color Management - A Practical Approach - Hemanshu Desai

Wed, 28 Sep 2011 15:37:18 +0530

Color Management means REPRODUCTION of ACCURATE colors, PREDICTABLY & CONSISTENTLY

In earlier days we had separate departments / companies who were master in their work. The designers, the processors and the printers were so closely co-ordinating with each other that there was hardly any chance of mistake. In the current era of digital processing, the skill of the each department is now in hands of individual and the vastness of the technology has actually loosened the grip on processing there by increasing the chance of accuracy. Accurate proofing thus becomes very important.

In earlier days, for proofing, we were relying on Progressive Proofs or Machine Proofs. The process was very accurate as it was kind of actual printing by using the same plate processing and maintaining same solid density on the same paper. However, the cost of proofing and the time that it used to take was high.

With the introduction of inkjet technology, a new era of proofing evolved and as of date it is matured. It is economical and faster compared to the earlier method of Progressive Proof. And as far as colors are concerned, it is highly accurate as well.

Before I discuss technology, let me touch upon some ideas that people have in mind about digital proofing.

- Cost of the proofing is higher on inkjet machines.

If we are comparing the cost with Progressive Proof it is not.

If we are comparing it with “color” outputs from Toner based devices, probably it is but what about accuracy? Is it real proof? Can a Toner based device produce 3 pl dot that an inkjet can? Can the heating element (fuser) heat the paper same on all the prints? (Heat is an analogue not digital technology).

If this was the case why should the international standards such as FOGRA have different specifications and tolerances for inkjet and toner based proofs.

- Can the system generate DOT like the offset printing?

Answer is no. It is impossible to produce on inkjet THE SAME dot as the offset. The RIPs are different, the resolutions are different and the size of the dots is different. There are systems which either generate dots or used generated dots for proofing BUT these are look alike and manipulated to the proofing resolution dots to give the impression like offset press. They are not THE SAME dots.

My question is; are we interested in looking and measuring dots for guarantee of the proofs OR we want to see THE SAME color?

The inkjet can not use the same media that I will print on.

Yes, the inkjet can not. It needs inkjet coated media. Practically, if you look at the varieties of the media used on offset and if it was possible to use the same media on inkjet, how many proofing sets do we need to make? Many intelligent RIP software generate paper simulation and print on the inkjet media to produce accurate proofs. And these are scientifically measurable and definable by ΔE.

Will you be happy if a proofing system gives ΔE less than one?

Let’s look at the process of setting up of the proofing system.

ORIS Color Tuner is the RIP software is certified by all most all the standards such as Fogra, Gracol, Pantone etc. We will look at ORIS for our understanding. The concept of ORIS is Hybrid proofing (Fig.1). It produces accurate proofs, generates soft proofs and also helps in the certification of proof. (Fig. 2).

Most of the software for this application depends on ICC profile. You have target profile (the offset) and printer profile (the inkjet). The software uses these to create the look-up table to match the colors. The drawback in this method is the software needs to take the CMYK Values and convert to Lab values and back to CMYK values. This double conversion at times looses the color accuracy.

While ORIS Color Tuner can work in the same fashion, it also give you the better technology of Automatic Color Matching. Let’s see how it works.

The setup of the printer and the calibration is simple and guided by the setup wizard (Fig. 3). The wizard helps you select the printer, do the linearization and finally the calibration. For those who want DOT, you can select here.

The first step is to linearization of the printing device. (Fig. 4). This step sets the tonal value from 0 to 100% in linear steps. Please note that on devices like Epson, once this is set usually you do not need to redo this for long for the same ink and paper until there is hardware change. For Toner devices this needs to be done 2 or 3 times a day.

After the linearization is done the Color Tuner software starts Automatic Color Matching. It gives you the option of specifying Total Ink Limit (Fig. 5).

Color Tuner takes the target profile (the offset profile). It prints the color charts and measures the Lab value of each color, compares with reference (target) adjusts the values, The printing and measuring process (iterations) is done over 3 to 5 cycles till the minimum ΔE is achieved. It also allows you to set the paper white, by measurement or by manual entry (Fig. 6,7,8).

The final result is highly accurate proof. But that’s not all. In case you have some colors which are very important to you and are not close enough, you can use the “selective color correction” method to fine tune individual colors. The ΔE can be further reduced here (Fig. 9).

The other feature of the ORIS is to handle the Pantone shades. With the built-in library you can use all the standard Spot colors. It also gives you the facility of adding your on spot colors. (Fig. 10). If you have multiple spot colors to be calibrated, you can select them and follow the same method of iterations and achieve highly accurate results.

 

Certification of Proof.
When some one gives us the hard copy proof how do we know it is accurate? But if the proof comes with Certification stating that is matched with a standard such as Fogra and the proof is with in the specified tolerance, will we accept it or not? Will our client have any issues? Unlikely.

The way Certified proof is to set up a target profile and the tolerances. While printing the proof, select a standard color bar that will be printed by the software (not the job) along with the job. Then use the simple device like X-rite Eye-one and scan the color bar. The Certified proof software will measure the same and compare it with standard values and certify it to be accepted or rejected proof (Fig. 11). The software can also print the label (Fig. 12) which can be stuck on the proof for sending it to the client. If you want you can also look at the detailed analysis to find out if there are any problems (Fig. 13).

So are we ready for simplified color management? Let talk in person.

Special Effects in Screen Printing by Michel Caza

Wed, 28 Sep 2011 12:41:13 +0530

SPECIAL EFFECTS IN SCREEN PRIINTING «A Golden Niche»
By Michel Caza, FESPA Board Member

As you know and in the frame of the huge FESPA campaign «IN SCREEN PRINTING, AS IN DIGITAL, BE IMAGINATIVE», we look for some «niche» of interesting and remunerating applications of our Screen Printing technology. We also know that, in screen printing, the purpose and the art is to transfer « something, almost anything » more or less liquid through our dear screen!!

One of the most interesting niche in the graphic and textile screen printing fields is the printing of «special effects»: our customers want something « different » from their competitors and are prepared to pay a fair price for that… Those effects are also, in textile printing, a precious tool for the textile screen printer. The same customer that discuss each cent of a price for a simple high gloss spot varnish will accept a much higher price if we bring him a very special enhancement of his image.

I saw screen printing companies around the world that make their happiness and sometimes fortune in this specialty : in Poland, in Bulgaria, in France, in Japan, in China and here in India…. That is why FESPA in a huge effort for improving an idea born a few years ago in the German Association had been creating one of the « Sensations » of the FESPA 2007 in Berlin, four years ago already, through its beautiful and useful portfolio named … « SENSATIONS »!

WHAT IS THE PURPOSE! AND THE TARGET ?
It is to catch suddenly and strongly the attention of the final user. It is to bring him news « sensations » from an AD product which can be of course printed or produced initially with different technologies, offset, digital and screen printing.

This is obtained by the addition of some surface effects that will catch one or several senses of the user : first « the view » of course, then, « the touch » by the feel of it « the smell » and why not, sometimes, « the ! taste »; for « the hearing », it is quite rare, but some researches may bring this possibility And of course, sometimes, several of those effects can be used on the same item, display, print and so on. It can also replace, often at a lower cost, some other technologies (hot stamping, doming, silvering, micro-embossing for ex.)

WHAT «ACTIVATES» OR MAKES WORK THOSE DIFFERENT EXCITING PRODUCTS?
It is interesting to know that they can be classified in different categories that belong to the principles of physics, chemistry or both combined….

The sun, some other sources of UV rays including « black UV », the temperature – warm or cold -, physical aggression such as scratching, dispersion, absorption and restitution of light, interference or incidence of light, reflection of some types of light, magnetism, the water to activate or to eliminate! The discovery of a different « process of activation » can bring you the idea of a special effect : that’s how I had the idea to create special effect based on the use of black UV lamp, tube or spot to create safety inks for banknotes or passports (engendered by a Wood’s lamp) and, incidentally, to use them as the starting point for these inks we studied and manufactured with Guy Massé at Dubuit Inks was based on some of those principles used for security, but here adapted to POP.

HERE ARE SOME OF THOSE SPECIAL EFFECT INKS AND VARNISHES:
PURELY VISUAL EFFECTS :

Gloss, Satin or Mat Varnish Fluorescent Ink

Glitter Ink and Varnish

Glitter Ink and Varnish Hammer Effect Varnish

Mirror Inks

Tilt Effect Inks

Tilt Effect Inks

Liquid Silver Inks

Liquid Silver Inks

Metallic Inks

Pearlescent Inks

Daylight Active (Photo chromic) Inks

Luminescent Inks (Reversible)

Security Inks (Reversible) and their POP Appl Heat Activated Inks (thermo Inks) - Reversible

Thermo Black Inks (Non Reversible Above 60°C)

Fading Inks (Non Reversible)

Just Add Water (Definitive Image Once «!Revealed!» = Non Reversible)

Water Removable Inks (Tattoo And Other Applications) – Non-Reversible

Water Removable Inks (Tattoo And Other Applications) – Non-Reversible

VISUAL & TACTILE: Structured Varnish (Visual and Tactile)

VISUAL & TACTILE: Structured Varnish (Visual and Tactile)

ABRASIVE INKS

ABRASIVE INKS

TACTILE EFFECTS : Tactile varnish (sticky & texture), Tactile varnish (egg scale texture),

EFFECT THROUGH SCRATCHING: (to remove or to smell), Rub Removable Inks (Scratch), Rub Removable Inks (Scratch and Sniff = Perfumed Inks)

PHYSICAL EFFECTS: Ferrous Inks (Ink for Magnets)

Blackboard Inks (Visual, Tactile, Physical)

And Guru’s ‘SPECIAL’ prescription : Of on the same image or item, several of those effects can be combined. But how to combine these effects with images printed with other technologies?

Think about that, of course, if you do everything by yourself including offset printing for example, or not, the whole of the operations must be integrated in a manner to be usable in the workflow of your production or in combination with the one of an external supplier. ! The main problem is of course the adjustments of registers, knowing, for example, than, in offset if each sheet printed simultaneously in four or six colors is perfectly registered, it can be some differences from one pallet to another.

Despite any type of screen printing press can be used (including manual and semi-automatic), the best presses for that kind of work remains for me the cylinder press with automatic feeding, for reason quite often combination with offset, of speed, productivity and quality of result.

And, for the same above reasons, the UV technology is also the best available one in the present and the future, both for technical and environmental reasons.

WHAT ABOUT PREPRESS?
If we speak about the image, it is clear that the file for the « special effect » films imaging or for the CTS technology must be planned together with the one of the original image. As it is quite often question of « spot effects », the register problem is crucial and requires a perfect control off the different elements of the image..
Don’t forget that some special effects will have to be entirely « designed » or separated from parts of the original image : this means that either a studio or an individual that created the image and/or yourself are able to prepare the needed proper part of the file! : this is of course very important.

AND THE SCREEN ?
If we speak about the screen, the choice of the fabric and of the stenciling technique are crucial.
It is of evidence that, if you need a very thick deposit of varnish or sometimes of ink, you will have to use a fabric that can be, in some occasions, from 10 to 20 or of 43, 68, 77 threads/cm… Or also in other cases, 120 to 150/cm…

Follow the instructions of the ink or varnish supplier. The stenciling - multi-coats with direct emulsion (difficult to control and to develop above a certain thickness) or capillary films system - is also very important : Braille, very thick varnishes, HD, big particles contents (pearl, sparks, metallic or abrasive effect inks) requires coarse fabrics and some times very thick stencils : and, in this case, the most simple is to use 250, 350 or even 500 μ capillary films screened (as sometimes in textile printing) either directly or through the help of « direct-indirect » technology with a direct emulsion coat in combination. Fortunately, many of the « special effects » can be used in UV with the very classical 140, 150, 165 fabrics, calendared or not and an as classical direct emulsion coating in thin coat.

Don’t forget that 50% of the ink coat is determinate by the fabric and 20% by the stenciling system.

PRINTING ? TAKE CARE OF COMPATIBILITY
As those effect will quite often have to be overprinted on inks and/or substrates printed with other
technologies (offset, digital printing, flexo, hot-stamping, transfers, etc.) a huge care must be token about this compatibility.

A simple example ? Even, for a simple high gloss spot varnish above a classical offset print, be sure that the offset inks are « over-printable » : this means that they must not contains any wax, or worth, silicones, or of course that the so classical « automatic powdering » has been eliminated by the offset printer through a careful automatic brushing.

I told you, the quantities involved are often very high. Cylinder press is certainly the best tool at a speed around 2,000/2,500 sheets per hour (in 50 x 70 and most often according to offset data, 70 x 100 cm. Here again, a part of the speed is related to the ink or varnish consistency, thyxotropy and rheology. And you need to know very well your technology and the way you use it.

The squeegee blade shore can vary between 55° and 85°, according to the substance transferred. The flood-bar can be thin or thick according the above seen necessities.
Curing, as we are more and more and will be more and more UV, depends upon the type of UV ink of varnish and of the thickness of the coat : is useful to know that in UV systems, a varnish how thick it can be (even several millimeters), will cure easily and instantly.

For metallic inks or some other printed chemicals, it have to be tested and set at very different speed and light intensity for example!:

Once again, you must know and master your technology.

SOME TECHNICAL PREPRESS DIFFICULTIES?

Here, I simply think about the manner to make the files for the use of RGB inks revealed through
the use of black UV light with Wood lamp. Just as an example of a new way of thinking required.

Let us take the « Girl face » for Dessanges. Starting from the RGB image, you must first turn Red, Green and Blue, the colors you will have to print with those special RGB inks that, in addition, give White (and not Black as the subtractive inks CMY will give).

That’s an example of the first trap : you must think differently, as matter of fact, exactly the contrary than when you think CMY printing!: «!subtractive!», not « additive » and, worst use a « negative » of subtractive. Only an apparent but quite logical paradox. But here 100%+100%+100% = …WHITE !

HOW TO SELL THIS TO YOUR CUSTOMER
Marketing remains a key issue : if no one knows what you are able to produce with the highest control and offer of those special effects, how will you make money with it? Crystal clear!

That’s the key of your success and that is also the point where FESPA can help you with this fantastic « SENSATIONS » book.

Just buy some of them for your company in a manner that you and each of your sales people can have one of them to show your actual or potential customers, and – eventually – have some to give to your best customers or their studios or creators to « give them some quite possible good ideas ».

We, at FESPA, consider this Big Book – the SENSATIONS portfolio as an « help » for our members to exploit this fantastic « Golden Niche » possibility : a nice tool helpful in any circumstances…

But only an help and a tool : the real work will be yours. On one hand to exploit the idea we or I give you - on the other hand, and mostly, to adapt those possibilities to the problems of your customers, but, and that’s the most important, to imagine, create, manufacture and print a lot of new ideas and effects that can be yours and yours only.

And here, we reach now the last and ultimate point :

SUGGESTIONS TO THE INKS MANUFACTURER

In general, you are not a specialist of Chemistry and Physics… If I am, that is simply related to my background and my years of experience and work with the manufacturers, but this is may be not true for many of us in our field.

So, when you have what you think as being an « excellent idea » about an original and new effect that can be achieved through screen printing, ask one of your manufacturers if he have an idea and a possibility to manufacture the product you need : I am sure that companies such as Dubuit, Marabu, Naz-Dar, Nor-Cote, Sericol, Sun Chemical, VFP, Wiederhold, or many other smaller companies will have the technical ability to manufacture those products : be simply clear and precise about what you exactly need to answer to or even improve the desire of your final customer and I am quite sure that some of them can have the technical ability to manufacture the exact product you need.. This means that you must be «!imaginative!» in front of your customer… And «!convincing!» in front of your supplier to obtain exactly the product, new or more classical, you need!!

AS A CONCLUSION, your destiny is in your hand ! In the right way of my belief, I think that if we – FESPA - and some of us can help you, the main decision remains yours – image makers or even better, « image improvers » - and yours only!!!

What is so special about screen printing?
“Sensations”, a campaign presented by FESPA is designed to promote the diverse possibilities offered by screen printing, thereby revealing just what screen printing is capable of. The campaign is directed at printers, printing customers and creative and marketing professionals, and aims to highlight the multiplicity of special effects achievable with screen printing. The most significant advertising material used in this campaign is the lavishly illustrated FESPA ‘Sensations’ book which has been produced by European screen printers.

The book shows 23 special effect inks which may be used for high quality designs in many different ways. This has produced a comprehensive printing work with exciting, inspiring and breathtaking screen printing effects. The inks used range from luminous to tactile, glittery to reflective as well as from heat sensitive to fragrant. The Sensations text is in English, French, German and Spanish and its ring binder format permits the addition of a fifth language.

Screen printing competes with many other media and technologies for its share of company marketing budgets. ‘Sensations’ reminds people of what is so special about screen printing – the possibility of bringing a print to life through the use of special effects that no other printing process is able to offer. Screen printing creates prints which can be seen, felt and smelt.

Image Optimization by Mike Ruff - Nazdar Cosulting

Wed, 28 Sep 2011 12:14:34 +0530

It is all about optimizing files to print more accurately in screen printing with a bonus of 20% to 30% ink consumption reduction.

Since the Spring of 2008, the print industry has been buzzing about the words “Image Optimization”. In this short article I hope to impart an important understanding of what the fuss is all about and how legitimate is the fuss. Those that have taken time to investigate image optimization are seeing an increase in productivity and much needed profit margins in all types of printing - screen print, offset, digital and flexo.

The product that has emerged in the last two years is “Image Optimization” Software. It is new. It’s not and an old technology just re-invented. However, just like a great song that comes along every decade, some old products with similar characteristics claim to “do the same thing”. They don’t. I hope to show an example of the new technology and encourage you to get moving on printing better, printing more accurately and saving a lot of ink at the same time. Image Optimization will do that for you if implemented properly and you do not get sidetracked by products that appear to be the same thing but are not.

A Brief Explanation of Image Optimization:
“Image Optimization” is not the same as “Ink Optimization” although they both save ink. The primary difference is image optimization improves print accuracy and ink savings is a side benefit. On the other hand ink optimization has been around for years in the form of GCR. For those that may not know the term GCR, it is an acronym for (Gray Component Replacement). In process color printing, when the three chromatic colors, CMY, overlap they produce black. (Really, it is dark gray.) This is called the “Gray Component”. Some people a lot smarter than me figured out that most of this “gray component” could be replaced using a black dot thus saving 3 colors of ink and increasing only one - black. This is saving ink.

The printing industry also soon found that by using heavy GCR, color was much easier to control on press. GCR immediately found a home on the Screen Printing Presses and Flexo. However, the euphoria quickly waned as less knowledgeable prepress people overused GCR and produced questionable results such as grayed out shadows, hard breaks in flesh tone shadows, black trees, black purples and auburn hair turning black. The problem with heavy GCR is, it is a non-colorimetric creation of a black channel causing unwanted color shifts in certain color combinations. The result in some images was good but in other images it could be a disaster.

Some prepress people went off the deep end the other way and stopped using GCR in any form. They said, “We only use UCR.” (Undercolor Removal). Of course this was an over reaction because UCR and Light GCR were almost identical and UCR is an even less sophisticated way to create a black channel than GCR. If you look at Figure 1, you can see UCR and Light GCR are comparable with a slight edge given to Light GCR because the black channel is smoother. (Figure 1, UCR Compared to Light GCR)

Figure 1

Since the beginning of using heavy GCR to control color shifts on press, really good prepress people in the flexography industry have learned to use GCR in Photoshop in very creative ways such as creating several layers in an image. They would mask out areas that excessive GCR would destroy and only use heavy GCR in the layers where heavy GCR would work well. They used light GCR in layers that are prone to color shift. Then they simply re-assembled multiple layers and flattened the image. It’s beautiful to see the skill of some of these craftsmen as they make life good for the pressman. Highly skilled prepress technicians still use selective GCR and have multiple levels of GCR in the same image. This manual method is used regularly in the flexography and the screen print industry. The problem with Manual Selective GCR is, it is slow and the manipulation of the color is still not colorimetric. There are about 20 manual steps required in each image. It looks good, it prints great and the ink savings is there but it takes a very expensive prepress person about a half an hour to prepare one image.

Adding Ink Saving GCR to a RIP
RIP manufacturers soon decided they could add “Ink Optimization” modules to their RIPs and save ink. The modules just linked the image to a higher amount of GCR. It worked for ink saving and it helped in press control; however the color shift problem still existed. This is the “old technology” that is now claiming to do the same thing as the NEW Image Optimization Software we are seeing today.

Industry Buzzing (For good reason!)
Image Optimization is not GCR. It optimizes the gray component and provides better more accurate color, better press control and ink savings. “Image Optimization” is not just linking to different start points of GCR. “Image Optimization” removes neutral color and will add chromatic color (CMY) where needed to correct the output to the original intent. Basically, gray component is removed but not at the expense of color accuracy. This is why some are saying, “it is just GCR”. It is not just GCR. It is image optimization. The results are amazing and printing is becoming almost idiot proof with image optimization done correctly.

In order for you to see a comparison I have compared Light GCR (that is the most common conversion from an RGB file) to Heavy GCR that would be used by a RIP that is attempting to save ink through just increasing the amount of GCR. (See Figure 2, Light GCR vs Heavy GCR) Figure 2 proves that in some images Heavy GCR will adversely affect the color. Notice the grayed out shadows. At a casual glance it looks O.K. Upon closer inspection, there are some major problems with heavy GCR on this image.

Figure 2

Remember, on some images heavy GCR is fine. Photoshop default is Medium GCR. It works most of the time but optimized images look much better. The casual Photoshop user that converts their image to CMYK from RGB is using Medium GCR and they don’t even know it. The reality is, UCR and Light GCR look about the same. Medium is good for most images and prints better than UCR and Light GCR. Heavy GCR is a risk if you don’t know what you are doing or not paying attention. Really good prepress people in the screen print and flexography industry can navigate these waters with Heavy GCR and even using selective GCR to produce some amazingly good results.

For those of us who are not as skilled, “Image Optimization” has automated this process for us and as a bonus “improved” the image quality and accuracy by doing the job colorimetrically. (See Figure 3, Image Optimization). If you look at the three images on Figure 3 you will see the heavy GCR image has some major problems in the neutral shadows. The rust colored sofa is grayed out in the shadow. The blue dress is shifting to purple. The emerald background shadows have no color left in them. This is an example of removing gray component by just linking to a higher GCR setting.

Figure 3

Now notice the optimized image on the right. The color has actually been improved and it used 21% less ink than the light GCR image.

In Figure 4 I turned off the black so you could see what the software is doing to the CMY colors while removing gray component. It is obvious why the color looks better in the optimized images. (See Figure 4, Color Managed Correctly) Notice the original Light GCR conversion and compare it to the optimized image. The color has actually improved. Optimization added color! It saved color where it could but added color to make it more accurate to the RGB file. If you look at the three colors down you see that there are major ink savings in heavy GCR and also the Optimized Image. On the heavy GCR there is ink savings but it has an unacceptable color shift. On the optimized image there is actually 21% ink savings with better color and idiot proof printing. It will print very accurately on a screen or flexographic press.

Figure 4

I hope this quick example will encourage you to put some time and effort in “Image Optimization”. Here’s (3) reasons to get moving on image optimization.

1. Prepress Dream: If you handle 10 files a day manually and spend a half hour manually manipulating files to help them print better and save ink, you are spending 5 hours of prepress time a day or 1,040 hours a year. (Not very productive.) Multiply this by your hourly rate of prepress labor and you will see a major profit drain. Color can be more accurate and predictable with this new optimization software.

2. Ink Savings: For every $100,000 your company is spending on process ink each year this example of 21% ink savings has the potential of saving up to $21,000 a year. This is pure profits because it’s just like finding money dripping off an over-saturated press sheet.

3. Improved Accuracy: Image Optimization will produce optimized press control while insuring color is correct. We have been seeing setup times on press runs drop as much as 25% due to Image Optimization. The financial return on reducing setup times by 25% is a lot more than $21,000 per year in most printing facilities.

In Conclusion
I have purposely not named image optimization systems. I do not want this article to be an advertisement for any particular software or system. I feel I have explained the difference. Matthew 7: 16 says, “Wherefore by their fruits ye shall know them.” If the software just links to a higher level of GCR to make prints run better and save ink, it is ink optimization. If the software colorimetrically converts files with color accuracy as the primary goal and neutral color is removed where possible, this is “Image Optimization” Software and you will be amazed with the results.

(**This article was first published in the Screen Print Magazine.)

Why manual screen printing is tougher - Mike Young Part 1

Tue, 27 Sep 2011 18:47:35 +0530

Why Manual Screen Printing Is Tougher Than You Think! - Part I

An in-depth two-part article about the powerful influence of mechanically flooding a screen―a smarter way for repeatable quality print results

By Mike Young, Imagetek Consulting International, North Haven, Conn., USA

Early History.
When researching the archives for worthy technical articles on floodcoating (scraping the ink back over the screen following the print stroke), I found there were very little of interest on the subject―then completely void of anything related to its significance of printing anything that is considered demanding in nature. The latter could typically include many high-end graphics, high-performance products, high line count 4-color process, numerous industrial / electronic applications as well as many products that are printed onto clear substrates. I am not surprised by this lack of information regarding the floodcoating function because why write about something that is largely seen as being nothing more than an inconsequential contraption when industry’s screen printing technical experts seemingly have much bigger fish to fry!

In a sense, flooding the screen is a necessary function with conventional screen printing, in order to bring the ink back to the start so the next print cycle can commence. While I do not differ from that view per se in many instances, generally speaking, it is an entirely different ball game when the dynamics of the process is stacked against achieving desired results profitably. Moreover, people typically working in today’s printing environment, particularly those that uses the process to fabricate a finish product, do not have the same scope of experience or processing skills as top professional commercial screen printers have. As such, to make their job just that little easier to accomplish, the advantages of flooding in a controllable and repeatable manner, to produce consistent finishing results, must be foremost when considering the essential need to upgrade from manual printing to automation of any kind.

In the first part of his article, Mike Young compares the pitfalls of manual printing over semi-automatics for controlling deposit uniformity, repeatable finish quality, greater productivity and overall performance. He explains in simple straightforward terms a critical function that is missing from the process with manual printing.

Welcome to the wonderful world of screen printing.

Without question, screen printing is truly an artistic process that has been around in its recognised form for over 1000 years; a craft that originated in China where silk was used for the screens, thereby the term known as silk screen printing. Silk has since been replaced in modern times with more economical and stable alternatives, such as polyester―the most widely used woven material selected today.

Now fast-forward to the modern commercial and industrial world of printing. The screening process has been used very successfully by numerous manufacturers to fabricate finished products, including many, electronics, toys/games, communication (cell phones for instance), hi-tech and medical applications.

Nonetheless, in a sense, its versatility can pose to be a problem where consistent quality is a prerequisite for customers’ confidence. Since screen printing is largely an artistic process, it essentially means each print is slightly different, however insignificant, because the process does not allow itself to be duplicated in an exact form print after print―in much the same way an artist can paint the same scene or flowers repeatedly―but each will be dissimilar to some degree.

A repeatable ‘mechanical’ process.

If we look at the world of limited edition screen printed serigraphs for example, many are manually printed, numbered and signed by the artist. While they may be worth thousands, none of the prints are exactly alike, as they will have some registration and color variation amongst other inconsistencies. However, uniqueness and non-conformity is entrenched in the art world―Andy Warhol made a small fortune from his now-famous serigraphs; with the depiction of Campbell’s Tomato Soup and the collage of Marilyn Monroe portraits that are now world-renowned. If you are fortunate enough to scrutinize these offerings, registration will be seen all over the place and color from sheet to sheet far from being consistent. Agree, these prints may fetch millions of dollars but the majority of us would be thrown out of a job if we produced the same errors!

That is what screen printing is fundamentally about; reproducing images that are close to a likeness but are not exact, having their own distinct individual characteristics about them. In essence, screen printing is nothing more than an artistic process, to create either a two-dimensional image (for instance, the letter ‘A’ having height and width) or three-dimensional coating deposit (a solid often without an image). In the modern commercial and manufacturing world, this artistic craft has to be reconfigured in order to rid most of the artistic principles and creativity, which are no longer required, to make printing more of a repeatable mechanical process that can be controlled to a large extent.

Common misconception of ‘flooding’.

The only purpose of a floodcoater (also known also as a floodbar, scraper or scraper-blade) is to scrape back the ink―thereby flooding the screen in readiness to commence the next print cycle, is a widely held misconception (Photo 1?). While this train of thought maybe adequate in non-demanding operations, it is only by understanding the hidden benefits of the mechanical floodcoating concept has to offer can one begin to appreciate its true significant influence in obtaining constant repeatable print results―which is not possible when manually printing.

In fact, your writer has always promoted in quality-printing operations, large or small, that if used creatively the floodcoater is as important as the squeegee―or more, albeit, if only philosophically speaking. It has a greater influence that governs the control of deposit thickness, color uniformity and tonal representation for 4-color process more than any other single function of the printing process besides pre-press. To determine how powerful the role of flooding the screen plays in obtaining a finished print one must first examine the complexities concerning squeegee, together with its on-press adjustments, to fully comprehend how detrimental the floodcoating function can be to the whole process.

When a semi or fully automatic flatbed press (the degree of sophistication is irrelevant) has been set up ready for printing, most of the original variables become fixed for production (frame size, fabric grade, tension, emulsion coating thickness, RZ value, image size, etc).

Providing off-contact distance and the amount of peel-off are set reasonably well for the job, the only variable left to an operator has always been on-press adjustments belonging to the squeegee and floodcoater.

While the squeegee represents the single most important tool to achieve the desired results at this stage of production, the longer it is in length the less integrity it has to transfer successfully ink through the mesh evenly.

Squeegees have a tendency to collapse in the centre, an occurrence we shall examine later in the second part of this series. The scenario is then progressively made worse as the squeegee ends becomes closer to the inside edge of the frame.

Squeegee versatility....or vulnerability(?)
Although we often dismiss the squeegee blade as having only a few components to be concerned with, there are surprisingly at least 50 distinct prominent and individual working influential variables during the print stroke—all interacting between themselves according to equipment and usage. Not that one needs to be overly concerned with them all but listed nonetheless below for anyone interested in knowing what they are and given in no particular order of importance:

3 x quality grades (at least): low, medium and high

5 x durometer hardness profiles: single, dual, triple, 5-ply and various top/bottom composites (rather than back-to-back composites in its thickness)

2 x durometer material hardness: original when brought and its continuous natural increase gained in hardness due from use, abuse, exposure to solvents, light, etc

thickness (thicker generally less pliable)

3 x elasticity/flexibility: pliable, semi-rigid and rigid

2 x depths of blade: whole and free depth outside the holder

6 x edge profile shapes: rectangular (900 corners), rounded (bullnose), single and double bevel (flat & chisel/’V’ shape), diamond (see Fig. 1?)

2 x sharpness: dull and sharp (smooth blemish-free regardless of profile shape)

2 x straightness: linearly straight along its entire length without waves (side-to-side) or deviations (up and down) while in the squeegee holder

5 x edge conditions: a) reused immediately after previous use (not cleaned/washed), b) washed with solvents after use and immediately reused without resting, c) washed and properly rested before reuse, d) sharpened and immediately reused and e) sharpened and then properly rested before reused

2 x lengths: correct and oversized

2 x pressures: overall squeegee bridge assembly and individually applied by each cylinder placed over a given area (not to be confused with the next)

2 x balances: blade physically out of balance in either direction (perhaps offset against two cylinders) and mechanically levelled to the print table once it is down in the print position regardless of pressure used to print

3 x angles: mechanically set, true print angle once flexed and increasingly but variable angle towards the squeegee ends (due to the fabric’s upward force)

3 x speeds depending on equipment type and setup: acceleration from starting position, maintained speed and deceleration to stop (operating whole or in part within the image area)

rotation: print side rotated 180º to the back side (memory loss as it conflicts with blade’s adopted memory)

2 x skewed angles: squeegee skewed (commonly known as ‘snowplough’) a few degrees in the direction of printing in either axis

2 x print modes: print / flood (loss of sharpness with increased deposition) and flood / print operation (reverse of the above)

Dwell: varying lapsed time between each print stroke

Camber: creating a slight convex curve along the entire edge (a consideration only for long squeegees)

As seen, there is an incredible amount of intermingled components that creates too much vulnerability in the workplace; changing any one will alter the outcome of others as well as print appearance to a degree―some considerably more than others. Moreover, since the effect of each physical trait tends to overlap by ostentatiously merging with others, assigning responsibility to which originated a positive or negative result in print appearance would be difficult to quantify individually. Despite this, the squeegee’s on-press variables are directly responsible for initially controlling the following:

Ink transfer by deposit weight
Edge definition
Image resolution
Overall clarity
Initial color likeness
Repeatable close tolerance registration
Dimensional size / shape (distortion-free)

Deposition or Definition.

The squeegee is therefore such a powerful tool it can become a hindrance to the printing process when excessively adjusted or haphazardly played around with. As a result, when making a single adjustment, the likelihood is that it will affect other interfacing variables to the print finish due to its influence overlapping in nature. For example, simply applying more pressure will also alter true (actual) print angle (unless otherwise compensated), which increases deposit but may also reduce edge definition. A shorter depth squeegee blade than one just previously used will reduce flex (give) and will consequently change actual print angle (deposit). When the blade’s edge hardens as it wears down, it will increase its effective hardness as well, thereby potentially reducing overall deposit thickness.

Even indirect press adjustments can change squeegee’s printing characteristics; lowering off-contact distance will render more squeegee pressure (and print angle) unless compensated for with many equipment designs. The innocent action of slowing down the squeegee tends to increase contact pressure, which affects true print angle and subsequently deposit thickness and image definition too. This is the reason why printers reduce squeegee speed when encountering print problems upon setup and conversely why they often find superior edge resolution with higher speeds!

Keep in mind that while this article concerns the function of mechanical floodcoating in a consistent manner for repeatable results, it is impossible to yield a smooth uniform ink deposit when manually printing with a squeegee regardless. Irrespective of how experienced print personnel may be, print results from manual printing can never be close to consistent due to the multitude of unpredictable squeegee variables interacting between themselves between each print stroke and printer throughout the day. The situation is not any easier when manual flooding is added to the necessities of the screening process.

These realities of these facts are mentioned so that personnel printing become aware that any sort of change can result in a different and possibly complex outcome, not all of which may be desirable for the job at hand. This is why one hears too often that a positive result from one adjustment made yesterday does not seem to work today. Chances are it is due to some other variable (component) that has also changed unknowingly to the printer.

The one thing we have learnt so far when looking for consistent repeatable print results that can be duplicated anytime―manually printing is not exactly the best way to go. For whatever reason, companies sometimes have little choice but to continue with manual printing, but now they have a much better understanding and appreciation of the challenges faced in keeping its present print quality at status quo.

Manual Printing.

A number of companies complain about their high reject rates together with deliveries continuously being pushed back. I share with them that much of the problem is not necessarily that they were doing anything wrong, or even their inability to screen print satisfactorily but, rather, experiencing nothing more than enjoying the inherent traits (read―shortcomings) of manual printing.

Manual printing is far from being an exact process and was never meant to be no matter how well one tries! Not that it helps any printer in dire straits to hear this, but inconsistent results is simply the outcome of an artistic craft carried out manually and, like any craft, each will be different. Perhaps they were be doing a magnificent job under the circumstances for all I know, however, there lies the crucial difference between ‘manual’ and ‘automatic’ printing―the so-called pitfall of not being able to mechanically control the process for demanding type jobs. For hassle-free production with excellent print results, printers should be in the driver’s seat as master of the printing process and not the other way round.

In the second part of his article, Mike Young looks at the significance and beauty of the floodcoater when comparing semi-automatics to manual printing for controlling overall performance.

Respectfully submitted by Mike young
Imagetek Consulting International, April 12, 2011

Press accuracy with no proof - Mike Ruff-Nazdar Consulting

Mon, 3 Jan 2011 14:42:41 +0530

A file may not be accurate to the photography and the customer may not even like it, but the printer has only one responsibility in reproducing a digital file if the client does not provide and accurate proof. “Print the file accurately on press”. But how do you do that?

Question:
If I were to give you a digital file and you printed the result of image 1a (See Figure 1a) and your competitor printed image 1b, (See Figure 1b) who has printed the image accurate to my digital file? Your answer is probably, “We have no way of knowing which one is accurate without an accurate proofing target.” But I submit to you that there is a way for you to know you are accurate to the file on press.

The Answer:
The way you would know your print is accurate is to pint the digital file without adding a color cast to the image. A color cast occurs when we add more red, green, yellow or blue through our printing process than what was intended in the original file. Therefore, a color cast is added when we do not print in balance. (See Figure 2, Color Cast Example)

In this short article I will address a simple way to ensure and prove that you are printing in balance and accurately.

Starting with a calibrated monitor
A calibrated, neutral gray, balanced monitor will display an image very accurately. If the monitor is neutral, it will not be adding a yellow, red, blue or green cast to the image. This is the primary goal of a calibrated monitor. Neutral gray calibration is what drives accuracy to the file. If we trust our monitor and we know it is not adding a color cast to the image on the screen, we will have confidence that what we see on the screen is very similar to what the client submitted. The reason for our confidence is we know we are viewing the file in a neutral condition and our monitor is displaying an accurate image. A good first monitor test is to just look at a good neutral gray image on the monitor. (See Figure 3)

RGB neutral is equal Red, Green and Blue. An example is midtone gray is 128 R, 128 G, 128 B. If I make myself a calibrated print of this midtone gray value and the absolute densities of the gray sample print are balanced, I can compare the neutral gray of my proof to see if I have a color cast on the monitor. If you see a color cast, recalibrate. Gray calibration will be the primary part of all calibration software. Once your monitor is neutral, what you see is very similar to what you should produce on press except for the deep saturated colors of RGB that are out of your color print gamut. Now that our monitor is neutral, if we print to neutral on press the image will have a similar appearance to the neutral monitor.

Moving Though the Workflow
As a digital file moves from the computer to the film or direct to screen, again the important objective is to maintain neutrality. We do not want to add a cast to the file by imaging screens with the tonal values out of balance. An example of what might go wrong in screen making is, if I were to use the wrong mesh on one screen or over or underexpose a screen, then I would not have a balanced print. No matter how good of a printer I might be, I could never overcome an out of balance set of screens. One color will dominate the others and I would get a color cast. The objective is to have screens that are in balance and a repeatable process so I can print in balance.

Printing in Balance
Printing in balance is a very easy thing to do if you have carefully managed the workflow. But a printer that does not understand printing to neutral can still mess it up. Printing to neutral is just printing C, M and Y tonal values that result in an equal response. (See Figure 4, Balanced 3-Color Gray Densities)

This can be measured using a simple densitometer set to absolute density. You DO want the value of the substrate in the density reading because we want to neutralize the substrate by managing the tonal values. Do not use the minus paper setting.

If I have an in-line press, it’s much easier because I can print the C,M and Y in a quick succession and I then just take a measurement of the gray value. The numbers should be equal. For example the midtone gray should be close to .59 Cyan, .59 Magenta and .59 Yellow. (Neutral) The gray would look natural and neutral. The process image I am printing will look very much like what I saw in the monitor. (See Figure 5, Balanced Midtone Densities)

If I use a one color press, I simply print the cyan first. If my final target is .59 density of cyan in the gray patch then I need to print it a little lower knowing I am going to pick up some cyan from the contamination of the other colors, magenta and Yellow. So I print the Cyan to about .50 density. (See Figure 6, Midtone Cyan Density) This is not “dot area”, “dot gain” or “TVI”. This is absolute density. This includes the color of the substrate.

Next I print the Magenta. When the magenta is printing on top of the cyan in the gray bar I want a balanced Cyan and Magenta value. For example my absolute density may now be Cyan .50 density and Magenta .48 when I read the two color gray. (See Figure 7, Cyan Magenta Balanced) When I add the yellow the goal is to have an exact balanced CMY response when I read the CMY tonal percentages. Normally, the three color gray won’t be exact but if I’m within a three (3) point spread between density values, it looks great and I will be producing an accurate image. (See Figure 5 Balanced Midtone Densities). If my goal is to print C=.59, M=.59 and Y=.59 but I get C=.57, M=.60 and Y=.58, it is going to look good. If I get C=.55, M=.57 and Y=.54 it will look good. But if the density spread gets more than 4 points off I begin to see a slight cast and I then know the image is not balanced. I can normally just adjust the press slightly to move the CMY values closer, If I keep the gray patches balanced and I print at solid densities close to standard, I know my result will be accurate to the file.

I hope this example of printing accurately is a help to you in understanding what printing accurately to the file means. Remember, this does not mean the client will like it. It just means you printed an accurate print of the digital file.

Happy Printing.

The power of neutral gray by Mike Ruff - Nazdar Consulting

Sat, 2 Oct 2010 15:13:28 +0530

Neutral gray is a term used frequently in the graphics-reproduction business but seldom put into practice correctly. The misuse of such a powerful tool is tragic, because neutral gray gives printers the ability to accurately show a client what their creation looks like and then enables the print provider to accurately reproduce what the client intended for their final product. The principles of neutral-gray printing apply to all sorts of processes, screen and digital printing among them.

Neutral gray is so potent that when it’s applied after the printer addresses solid ink color, times for press setups that require critical color output can drop by more than 50%. The process involves simply correcting the solid colors, then calibrating and printing to neutral. There is power in understanding neutral gray, and this article will explore how to harness it to benefit print production.

Color control:
Unfortunately, our industry has accepted a culture of visual color control. What a disaster! We forgot neutral gray and print accuracy. We even forgot to teach our prepress people and press operators about neutral gray and print accuracy. The introduction of the inline press had screen printers inviting clients to come and stand at the end of the press and sign-off on their creation. Neutral gray didn’t matter. Accuracy to a print target was replaced by subjective opinion and hours of wasted press time. I’ve even heard production managers explain to clients that screen printing is not capable of matching a proof. Now I see the same behavior among users of wide-format digital printers.

Hours of wasted press time wasn’t so bad when prices were high, competition was weak, and runs were long. That has drastically changed. Runs are not long. Profits are not large. We just cannot afford to use very expensive screen or digital equipment as proofing devices. The solution is fourfold:

1. Make sure the clients see an accurate visual representation of what they have created.

2. Make sure we create an accurate visual representation on the color target proof.

3. Print an accurate visual representation of the file.

4. Approve color based on an accurate visual representation of the file.

Proofing and printing to neutral gray is the means of attaining all four of these solutions. Anyone can get the solid densities and ink hues correct through proper fingerprinting, working with the ink sup-plier, and good color-management tools. But having solids dead on the color target only guarantees that the solid colors are correct. Even having dot gain equal and correct does not fix errors in substrates and ink hues.

Most four-color process images are not solid. In fact, very little of the image has solids in it—unless you‘re printing cartoon art. So in addition to controlling the solids, if we nail the neutral gray, everyone wins. From the client to the owner of the print shop, everyone moves forward at hyper-speed. This is why Don Hutcheson and IDEAlliance developed G7, the most successful color productivity/color-calibration specification in North America. This is the power of neutral gray. This simple solution is taking the sheet-fed offset industry by storm. Gray balance is back because printers have decided that it is a lot more fun to make money printing rather than allow press operators to become artists.

Neutral gray defines accuracy:
We normally can’t control how or where the images we use for print production were created or how the creator viewed or assessed files we receive. Our objective is to just produce the file we receive accurately. The challenge is defining accurately. One definition you can always substantiate and back up with fact is as follows: Accuracy in the print industry means producing a client’s file with no color cast. This means we do not add a red cast, a blue cast, a green cast, or a yellow cast. We print to neutral. We can measure neutral gray and easily explain it because gray balance is not subjective (Figure 1).

The power of a neutral monitor:
The creator of a file and the person who inspects and prepares the file for output must pay attention to the monitor. You can judge the accuracy of a monitor by determining how well it maintains the neutral gray. I know the brightness and other gamma corrections are important; however, color inaccuracies show up in the grays. If the grays are neutral on the monitor, then what we see has no color cast. The image on screen is a very accurate representation of the file. You can test this very easily with an RGB file. Post-Script Level Two divides color into 256 gray levels, including white and black. One half of 256 grays is gray level 128. This is your midtone gray. So you can easily build gray level 128 midtone gray in Photoshop. Set the RGB color to 128 red, 128 green, and 128 blue. The color you see should be neutral. In other words, you should not see a red, green, blue, or yellow cast.

Having a neutral gray also gives you a chance to perform a simple gray-balance test in the Adobe Photoshop’s Variations mode (Image>Adjustments> Variations). The Variation mode gives you color choices on images you view. You can see the neutral gray shift if red, green, or blue shifts in the variation’s pallet. This demonstrates how gray balance is powerful in shifting the color. You also can be assured any color correction you make to the file will show up on a balanced gray color bar viewed on a monitor.

Neutral gray in proofing:
I’ve rarely found a proof that is neutral in my travels to numerous print shops around the country. And seldom have I found a digital printing device that is calibrated to neutral. Our industry should be disturbed because the printer is actually showing the client a color cast he has added to the file. This leads a lot of finger pointing between the client and the printer when the client produces a proof and the printer produces a proof and the two do not look the same. Who’s right?

There is a way to confirm who’s right. Figure 2 is a proof a client submit-ted and a proof the printer has proofed and confirmed that his press will match. Which one is right? Neutral gray’s power eliminates subjective opinion a-bout whose proof is accurate. In Figure 2, there is no way to tell whether the client’s proof or the printer’s proof is correct. But what if they both had a neutral gray bar on them? Look at Figure 3. We could easily determine whether the original file had a cast or if it was just the proof that was wrong. In this case, you can see that the file does have a green cast. The client’s proof looks good, but it is not accurate to the file.

The worst thing a printer can do is unknowingly take a client’s proof to press without verifying that it is correct. You can take a measurement in L*a*b* or even with a densitometer in the All Densities mode. It is critical that you begin the print process with a color target that’s verified and accurate to the file.

Neutral viewing of the proof and the print:
You may still see a color cast when you view graphics that you proof and print to neutral under lighting conditions that are not neutral. Standard viewing conditions for the graphic-arts industry specify 5000ºK lighting. Other important specifications, such as neutral-gray surroundings, light angle, etc., go along with the call for 5000ºK lighting. All these specifications are detailed in the most recent version of ANSI PH2.30 and ISO 3664 Color Evaluation for the Graphic Arts Industry.

Neutral viewing is important because we do not want an unbalanced lighting condition to add a color cast that is not in our proof or print. Some printers say that a client’s retail store is not neutral, so why does it matter whether they view the prints under 5000ºK light? The answer to this is simple: You probably cannot control this situation unless you only print for only one or two clients and you are their only printer. In real-world printing, the objective is for the printers to have their processes under control. That means producing neutral results. So, an important part of that control is proper viewing conditions (Figure 4). The power of neutrally lighted viewing conditions is the assurance that you’ll not see a color cast added by the lighting. This can save hours of press time, prevent a rejected job, and help retain a client.

Neutral on press:
Once you produce a neutral color target and you are confident the color target is accurate, the next challenge is to produce the file with no color cast: neutral. ISO 12647-5 is the specification for screen printing. ISO 12647-5 says midtone neutral gray is C=50, M=40, and Y=40. This refers to the tonal values of the file. If you output linear film from the file, the film would read C=50, M=40, and Y=40. There is no doubt that if you were to print film using these tonal values correctly on the right kind of paper with the right ink hues and densities, it would produce neutral gray. In the real world, we do not print on neutral paper. We some-times do not print with the ISO 2846- 4 ink sets, we do not produce the TVI (dot gain) specified by ISO 12647-5. So how can we achieve and maintain neutral gray printing?

The answer actually started with GRACoL in 1996. GRACoL defined gray in L*a*b*, not by TVI values. This was huge, but there were still some problems that had to be solved. G7 (not to be con-fused with GRACoL 7), developed by Don Hutcheson and IDEAlliance, solved the problem by specifying neutral gray and creating a Neutral Print Density Curve Specification. I personally have witnessed print facilities going from an average setup time of three hours to 45 minutes by just calibrating and training press operators to print to G7 neutral gray. Isn’t it amazing that such a simple process—one the we’ve had under our noses since color separation began—could move our industry so far so fast? That’s the power of neutral gray on press.

How to print neutral:
The first step in printing to neutral is learning to measure and know when you have arrived at a targeted neutral gray (Figure 5). GRACoL defined neutral on grade 1 and 2 paper. This pa- per is very white and normally doesn’t have very much of a color cast. Technically, midtone neutral in L*a*b* is L*50, a*0, b*0. However, visually we do not accept this. In my opinion, we have come to think that neutral gray must be slightly cool because it is the ugly step-sister of blue. I’m fine with that as long as it is documented as a specification I can point to and know when I have attained it.

True visual midtone neutral gray is documented by GRACoL 7 and specified by G7 as L*59, a*0, b*-1. G7 specifies neutral gray tones at the 25% area known as the Highlight Contrast (HC), the Highlight Ranges (HR) and the Shadow Contrast (SC) (Figure 6). What is amazing is when I attain this and then measure the color in All Densities mode on a calibrated densitometer, the C, M, and Y are almost identical. These results confirm that what I have is neutral and is not adding a color cast to the image. No C, M, or Y value overpowers the other col-ors. The standard viewer would have a difficult time seeing any specific color cast in the gray if they were evaluating it in standard viewing conditions.

So with the neutral gray defined and my proof color target neutral, all I have to do is adjust my C, M, and Y press curves to attain neutral values. Adjustments will necessarily change based on the substrates and solid ink colors in use. But because I am now measuring and targeting neutral gray, I can set up a press with a clearly defined objective and know that the pre-press work is clearly targeting neutral.

Setting the curves from a gray bar:
If we define the L*a*b* gray value of each tonal area in a tonal ramp and ignore the highlight in honor of the different substrates on which we may print, we’ll see an amazing result. Images appear very similar, even when we print on different substrates and our solid colors have slightly different hues. The reason for this phenomenon is that the gray-bar curve requires us to adjust C, M, and Y separately to attain neutral gray. This adjusts for substrate and solid-ink-hue error. Dot-gain adjustment does not address this. Even absolute density adjustments taken from pure color bars do not report the effect of color-on-color overprint. Taking the curve-value-adjustment numbers from a C, M, Y gray bar does. The G7 Color Calibration Specification uses a gray bar embedded in the P2P25X neutral-gray print target (Figure 7). Each tonal value is a gray built to neutral specification of L*a*b*. When converted to all densities, a neutral curve can easily be created that corrects for substrate and ink-hue differences.

Benefits to the client and the printer:
The client who understands neutral gray wants to work with a printer who also understands neutral gray. The benefit here for both parties is that neutral gray eliminates subjective opinion about the visual appearance of the file. Neutral is neutral, and you cannot argue with the purity of a neutral specification. The press operator who understands this can quickly determine whether the print is out of balance and which color is out with a modern densitometer that has an All Density function. As neutral gray becomes the controlling factor in a production facility, clients and printers find that communication reverts back to the professional language of the scanner operator who spoke of accurate gray balance with assurance in his voice.

The simplicity of neutral-gray color control is an example of Ockham’s Razor, a principle attributed to a 14th century logician named William of Ockham. It is often expressed as the law of parsimony, law of succinctness, or entia non sunt multiplicanda praeter necessitatem, roughly translated as: entities must not be multiplied beyond necessity. In today’s language it would be: all other things being equal, the simplest solution is the best. I believe that neutral-gray balance is the Ockham’s Razor for the printing industry. It works for print-ing and proofing in screen, digital, flexo, and offset, and it’s one of the most powerful tools we have to ensure accuracy and quality.

Roll of advance screen printing in Packaging

Wed, 8 Sep 2010 13:55:16 +0530

Recently I was invited by “Modern Packaging & Design Magazine” which is published by Infomedia 18 Limited to write an article on the role of advance screen printing in packaging as a guest columnist.

Many of you might have read my article if you are receiving their magazine, but if you have not read till now then here’s it…

———————————————————————————————

TECHNICAL ARTICLE, By Bhargav Mistry, MD, Grafica Flextronica & DMI
Published in Magazine “Modern Packaging & Design” Vol. 6, No. 1 | Jul-Aug 2010
(Copyrights remains with the publisher)

Screen printing process evolved over the years. Today, it offers ample innovation & creativity, thus playing a major role in packaging because of the availability of advanced screen printing machines, UV technology coupled with availability of innovative special effects inks.

Screen printing is a simple yet attractive process. The main reason is that in screen printing, the purpose and the art is to transfer something, almost anything more or less liquid through a screen!

It harnesses the natural phenomena of mechanical movement, flow and the interaction of liquids and solids. In screen printing, it is possible to attain controlled film thickness up to 300 micron. Besides, the printing medium – ink – can be almost any material that can be suspended in a fluid and which has a particle size that is ideally one third of a mesh opening.

Also, the visual impact that screen printing process can create is simply marvelous. The durability of the inks, the vibrancy of the colors, especially considering the harsh outdoor weather conditions for outdoor applications (sunlight, rain, snow, wind, etc) and its vast flexibility, all contribute to its unique capability. Screen printing is possible with any ‘semi-liquid’ product (various inks and dyes) on a number of rigid, semi rigid or soft substrates. Thus, these characteristics make it the most versatile printing process available.

Advantages of screen printing process

* High rub and scratch resistance, which is mainly required in industrial printing

* Vibrant color

* Due to availability of high quality screen printing inks with better light fast pigments, 3-5 years of outdoor life for any kind of applications can be achieved

* Wide range of substrates of various thickness, size and shapes can be printed easily

* Good ink film and mechanical stability allows to screen print on complicated and rigid substrates.

* Knowledge and process calibration provides high dimensional stability

* Screen printing enables to achieve a degree of flexibility that is unavailable in other printing process

* Flexibility of short runs to large industrial volumes

* Inks are available as per application

* Possible to print on fragile matters

Advanced printing technology

Quality in screen printing seems to have come a long way. Today, with automatic precision machines, it is possible to get a result that years ago would have been a dream. In the last decade, from a predominantly manual printing process there has been a big shift from manual operations to semi-automatic and NOW fully automatic printing machines. There are more numbers of screen printing machines sold today than it was five to ten years ago because it not only involves low investment which is a big advantage for those wanting to join the screen printing business, there is also scope for creativity. The screen printing technology today is faster, better and cleaner.

Despite any type of screen printing press can be used (including manual and semi-automatic), the best press for that kind of work remains for me the cylinder press with automatic feeding, for reason quite often combination with offset, of speed, productivity and quality of result. And, for the same above reasons, the UV technology is also the best available one in the present and the future, both for technical and environmental reasons.

UV Curing depends upon the type of UV ink of varnish and of the thickness of the deposit: it is useful to know that in UV systems, a varnish even thick of several mm, will cure easily and instantly. For example, for metallic inks or some other printed chemicals, it have to be tested and set at very different speed and UV light intensity.

Complementary role

Screen-printing is a fantastic technology that is used by many industries with so many old, new and not yet discovered applications – both flat (plastics, cloth, metal, thin to thick papers, sun-pack/sun-board, rubber, leather, wood, glass, ceramics, etc) and non-flat substrates, by using appropriate machinery and inks. Further, this process is also widely used for printing packaging boxes, duplex and sapphire mono cartons, labels and cards, UV effect on packaging materials for cosmetics, toothpaste, jewelry … the list is endless.

Special effects!

In this world of shopping and mall culture, buyers are attracted by the packaging they can see and/or touch. Before that tryst with packaging, they also carry the memories of advertising (both print and electronic), outdoor posters, etc. As they walk into the shop, first they are also confronted with eye catching POPs and POS posters, placards and other marketing gimmicks. Ultimately, the packaging in a shelf carries its look, its power of attraction for the consumers, and eventually the feeling of touch, or we can rightly say, today packaging is all about sensation – look, touch, feel, smell.

So, special effect screen printing is a great way to excite consumers. The range and variety of effect is extensive and it provides the marketer, print buyer and designer with a number of exciting possibilities they may never have thought were viable. This is because of the latest developments – machines and inks.

The most promising is the use of a wide range of ‘special effects’ thanks to the think tanks in the screen printing industry driven by FESPA, an international association of various national printing associations including India. FESPA spent a lot of resources to make a special book named “SENSATIONS” that shows many of those screen printed special effects.

The packaging can be printed through many techniques: offset, flexography, screen and digital printing or other. However, only screen printing allows to add those “special effects” enhancing the final product due to its versatility. These possibilities, combined with off set, digital, flexo or classical screen graphic, open a huge niche to many screen printers who will be able to offer customers truly enhanced and unique products and images to increase sales.

This is obtained by the addition of some surface effects that will catch one or several senses of consumers: The view or look of packaging which makes a initial difference – it is like first impression is the last impression … but now consumers want to touch by the feel of it and sometimes, why not rub and smell it. Amazing though, several of these effects can be used on the same item (multiple special effects, like we try at DMI institute). It can also replace, often at a lower cost, some other technologies such as hot stamping, doming, silvering under vacuum.

Specialty Inks & Varnish

The print buyers these days want something different from their competitors and are prepared to pay a fair price for that. They will accept a much higher price if the printers bring a very special enhancement of their product packaging image. So, one of the most interesting niches in the graphic screen printing fields is the printing of special effects, using UV special effect inks.

The inks available in the market range from luminescent to tactile, from glitter to mirror. The impact they can add to designs is breathtaking. Screen printing effect can enhance any marketing campaign and may give it that extra competitive advantage. One may also enhance the effect with ink or an overprinted varnish. Varnishes have become a popular finish on wise labels especially because it gives the graphics a much greater richness of color.

A gloss varnish over a matte surface is a more subtle approach that inspires curiosity. One sees a shape under the light or notices a smoother feel against a more resistant matte solid area. Similarly, coarse, high luster effects are created with thick coatings of varnishes that have large particle sizes. It is a striking way of printing reversed out images of icons or logos, an ice effect or extremely fine line patterns. A wrinkle effect can be created when a UV varnish is cured under UV-A light.

There are thermo-chromic inks. These are sensitive to temperature change and can be used for time temperature indicator labels. Irreversible ink types, which do not change back to the original color, indicate if perishable goods have been stored for too long or at to warm a temperature.

Packaging for the blind

For blind people, the “Braille” texts on labels or packaging are printed. Here, a thick varnish screen printed is widely cheaper than micro-embossing through die-cutting or embossing technologies. Embossing is a slow and expensive technique (for the tool itself). It can be easily replaced by screen printing of thick UV varnishes.

Security

The security feature of screen printing is immense. This feature can be used to protect the brand against counterfeiting or tampering. RFID labels are used to provide security and efficient tracking and tracing of products, cases through the supply chain.

I have a customer of mine in Mumbai who is into packaging (with offset and screen printing unit) whose clients are happy that he offers something different every time because of UV special effects which they feel a luxury value addition especially in case of cosmetic, and such luxury product packaging. He strongly feels that UV special effects are not only luxury value addition for customers but a ‘safety net’ as well. Because of the very nature of special effects, it will help the companies in protecting their brands from duplication.

RFIDs

One fantastic application of screen printing is the printing of both antennas and transmitter/receiver in RFIDS : Radio Frequency Identification. This is beginning to replace at short and medium term the classical barcodes that need to be caught at very short distance. The printing of those items, both on or inside of the packaging itself or on a special label to stick on or in, is ideally suited for screen printing in that sense that it is the best technology to print the conductive silver, carbon or nano-particle inks for the antennas or receptors.

‘Substitute substrates’

Continuous advancements and developments in polymer technology, expertise and cost-effective manufacturing, plastics is replacing traditional materials in many fields (environmental conditions apply!). These include : PVC, Polypropylene, HIPS, Lenticular Films, Polycarbonate etc. Polypropylene Sheets are extensively used for blister packaging, cardboard boxes etc. Polypropylene finds application in Disposable Containers, Embossing, Gift Box Making out of clear sheets, Freight Packaging, etc. The trend these days is to use a substrate with a low density which also makes it affordable. PVC Sheets and Polypropylene Sheets are the best suited for screen printing. Polypropylene as a material is very eco-friendly and can be easily recycled. It is accepted and widely used all over the world for different applications. It is preferred by screen printers because of its low density and very economical cost. Similarly, PVC for screen printing purpose is a very good option. A good quality PVC sheet makes a good surface for a screen print because it has a pre-coating on it; even if the material gets old the coating is never hampered.

Perfect expertise needed

The main problem is of course the adjustments of registers, knowing, for example, in offset if each sheet printed simultaneously in four or six colors is perfectly registered, it can be some differences from one pallet to another. In case of UV spot effects, the register problem is crucial and requires a perfect control of the different elements of the image.

Some special effects will have to be entirely designed or separated from parts of the original image: this means that either a studio or an individual that created the image and/or yourself are able to prepare the needed proper part of the file: this is of course very important. In PDF, the problem of layers and transparencies can be difficult to solve: it also depends upon the quality of the files received from the customer or its studio.

As those effect will quite often have to be overprinted on inks and/or substrates printed with other technologies (offset, digital printing, flexo, hot-stamping, foils, etc.) a huge care must be taken. For example, even, for a simple high gloss spot varnish above a classical offset print on paper or board, be sure that the offset inks are over-printable: this means that they must not contains any wax, or worth, silicones, or of course that the so classical automatic powdering has been eliminated by the offset printer through a careful automatic brushing.

Patience please

Screen printing is now quicker, cheaper, produces better quality images and offers a number of special applications. But advanced screen printing with high level of automation is not everybody’s cup of tea. Having advanced machines in place is not sufficient to run a profitable screen printing business. There is no profit “from the press of a button” like in digital printing arena. There is no short cut. Because not only does the set-up process take considerably longer than other techniques, but being able to truly master printing high quality images using the screen printing process also takes much longer, because there are a number of variables involved.

Today, there exist different systems designed to help the screen printers to achieve better result. But it revolves around the simple concept or standardization of the entire screen printing process.

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I hope you must have enjoyed reading…