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NOTEBOOK Useful Tips & Information © ITW Trans Tech An Illinois Tool Works Company |
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 TECHNICAL DATA: 21-Step Grey Scale Kit • Uses industry standard 21-step grey scale film • Enables determination of optimum exposure time • Means to monitor & control etch depth • Helps to test strength of exposure light source • Useful in setting quality control standards Each kit contains: 21-step grey scale film; sample of properly exposed cliché material for reference; blank sample strips; detailed instruction sheet. Available for: • Polymer Cliché Calibration Kit (#1410491) • Hydro-Foil Cliché Calibration Kit (#1410492) • Express-3 Cliché Calibration Kit (#1410497) Other useful supplies for making short-run, temporary clichés: • Washout Liquid R241 20L (#310020) • Washout Tray, Small 12" x 17" inside (#1413001) Large 14" x 22" inside (#1413002) • Washout Pad Plush Brush (#1413005) • UV Blocking Light Shield (#1424004) • Anti-Static Film Cleaner (#1411134) • StaticMaster Dust Brush (#1410486) • MBM-2840 Exposure Unit (#11400017) • MBM-3850 Exposure Unit (#11400018) • MBM-3882 Exposure Unit (#11400004) • UV-Blocking Filter Shields for Fluorescent Tubes: enable light-safe use of normal fluorescent lighting in clichémaking areas (#1424001). |
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Is Your Process Science or Black Magic:
Why Should You Grey Scale Test?
FOR those of you who make your own polymer cliches and, at some time, have had trouble making good plates, the following scenario may sound familiar: you just processed a polymer and tried to print with it, but something is wrong– no image… bad image… uneven image? Must be bad plate material, right? Or maybe the problem is in your process. Are you using science or black magic? Let’s eliminate the variables one by one with this mini-workshop on using the Grey Scale Test. different from the last.
For ITW Trans Tech cliché expert Tom Guastaferri's advice on How Grey Scale Testing Can Save You Money, click here.
Shown above: (from left) the industry standard 21-step grey scale; a typical processed Polymer cliché showing the break (arrow) at fourteen-and-one-half; a typical processed Hydrofoil cliché showing the break (arrow) at eleven-and-one-half.
Let’s start with quality of material.
Is the new material bent or discolored in some way? If it is, then you have defective stock. This must have happened in shipment or after it was received. ITW Trans Tech checks the quality on all of our polymer plate materials prior to shipping. Shelf life, temperature, storage conditions, flatness as well as other factors are monitored closely. Of all the variables that could have gone wrong, material is the least likely. If you have made a cliché successfully before, it is unlikely that it is the material.
Now, let’s look at your process, step-by-step.
The best place to begin is following the instructions. There is an instruction card in every new package with exact procedures for making a good cliché. If those steps are properly followed, you will likely make a good plate. It might be worthwhile to read them again just to doublecheck your process, step-by-step.
Time To Test ?
If all those instructions are being done correctly without satisfactory results, then you need to make a grey scale test. This test is used to measure the amount of light needed to expose cliché material to produce the proper etch depth. The test uses an industrial standard scale, a strip of film with 21 shades of grey, graduating from clear to solid black. Each step equals an increment of light. This scale is used as a control, a non-variable, against which to monitor the consistency of all the other variables in the process.
That’s why grey scale calibration must be done with each customer’s unit, at their location, with their environmental conditions, their materials and so on. Now let’s eliminate variables one by one:
A complete system for do-it-yourself clichémaking includes MBM exposure unit, 21-step grey scales test kit, staticmaster film brush, washout brush, film cleaner and blank clichés.
Time (Length of Exposure)
The most common variable in the process is exposure time. It may be a constant number for a while or it may change over time. That’s when you may need to test again.
Exposure Unit Function
Is your exposure unit defective? If the time is excessively long, the timer may be malfunctioning or broken. Its vacuum must also be adequate and consistent. If properly working, no air should get between the three layers: artwork film, plate and plastic cover sheet. Also, check the cover sheet frame for any bending or uneven seating. Good contact between the film and cliché during exposure is essential.
UV Tube Service Life & Quality
UV tubes don’t live forever; older ones will require longer exposure time. Also, check the distance from tubes to artwork film and cover sheet. If that distance has changed or has become too far or too close, it will affect the exposure. This distance must remain constant.
Film Quality
Check the artwork film. Is it good or bad? Can you verify it? Measure the density of the black areas on the film with a densitometer. If you make thousands of clichés, it would be worth the investment to buy one. This is the only way to determine black density. On scale of 1.0 to 6.0 (clear to solid), an acceptable black must be over 4.0 in opacity. Film with lower density will not make a proper exposure and therefore produce bad clichés. Another film tip: make sure you lay your film on the plate material, right-reading, emulsion-to-emulsion. This keeps light from leaking between the .004” space that is the thickness of the film. This little detail makes a big difference, but is a common mistake.
Chemistry
Check the chemistry of your washout fluid. If you are using some source other than ITW Trans Tech for this washout fluid, our instruction formula will not give satisfactory results. Or if it has become contaminated or improperly diluted, it will muddle the process as well. When in doubt about the formula, follow the instruction card and use our fluid.
Screen Tint Film
For artwork that requires a screen added, is the screen film from ITW Trans Tech? If not, is that film precisely calibrated? Are the specifications the equivalent of ours or not? Close may not good enough. Does it have the right line screen and percentage of dots? These details are important because the screen type and exposure control the depth of etching. We can verify that our grey scale test works with our screens. We can’t vouch for screens from other sources.
Consumables Detective Work
Check the chain of consumables for any variable in the formula. Alternate materials will produce unknown results. Here are the ITW Trans Tech short-run cliché materials:
• Polymer– alcohol washout (red) durable, highest quality (variable etch plate, must
use screen).
• Hydro-Foil– water washout (variable etch plate, must use screen).
• Express-3: (solid etch plate, when screen tint film is not required) alcohol washout.
For more details on our full line of cliché plates, feel free to contact your ITW Trans Tech Consumables Customer Service Representative at: www.itwtranstech.com
ITW TRANS TECH An Illinois Tool Works Company
475 North Gary Avenue • Carol Stream, IL 60188-4900
Phone: 630.752.4000 • Fax: 630.752.4460
www.itwtranstech.com
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