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Shedding Light on the Coating Process

(February 2008) posted on Mon Feb 04, 2008

Discover where mistakes are most likely to happen in the screen-coating process and what your screenroom staff needs to do to avoid them.

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By Gordon Roberts

Create a checklist that covers all the variables that can spell disaster on the press, and check every screen against the list before you release it to be coated. Here are a few of the essential points to cover. (I’m sure you will come up with many more.)

Does it have the correct mesh count for the job? Has it been properly degreased? Is it newly stretched, and if so, has the mesh been work-hardened? Is the tension correct across the entire screen?

If any of the basic criteria listed above are not correct, then the screen will not perform properly and your printers will struggle to produce a decent print. Most problems occur when the screen maker decides to cut corners and send out a screen that is just not quite perfect. Give your screen preparers the professional respect they deserve, and give them the right to refuse to expose a coated screen until everything on their checklist is complete. Initially, it may slow things down, but believe me, you will gain it all back on the press.


Second basic truth: Don’t try to rush the coating process

If you use emulsion that needs to be mixed, follow the manufacturer’s instructions to the letter. If the instructions tell you to let it sit overnight to allow bubbles to work their way out, make sure that you allow time for this. We all know that you can get something to work in an emergency, and the tendency is to start bypassing all of these little rules until you find yourself yelling at the manufacturer’s rep because his emulsion no longer works. If you scoop coat, make sure that the leading edge of your scoop coater is not damaged. If it does get damaged, make sure you replace it immediately. They are expensive, but you should always have a replacement on hand. Never use a coater that doesn’t give you a clean, perfectly flat layer of emulsion.

I am often shocked to find people using equipment that they should have discarded long ago—and living with the resulting problems. Also, I am shocked that employees use equipment in a manner that allows the tools to get so easily damaged. Treat all of your equipment with the respect it deserves.


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