Exposure Systems Your exposure system determines your success screen printing.
I once owned the finest automatic presses available, had a state of the art computer graphic system, and a sales force that filled my shop with orders, but never understood why I had so many problems on press. I went through many different emulsions, attended seminars, I knew how it should work but it didn’t in practice. Screens broke down quickly, especially on water base and discharge prints, and the pinholes were everywhere. I made the screens like I always did; same exposure times as always on an old carbon arc unit, but a thousand pieces into a ten thousand piece job the screens died on press, details fell off the mesh, or worse the whole stencil peeled away on a discharge job due that afternoon. I rushed to the screen maker, “I need another set of screens for the discharge job on press three,” and quickly walked away. The screen maker pulled some screens out that he just coated, patted the surface to make sure they were dry and burned a new set, developed them, applied hardener, and force dried them in front of a fan. As soon as they felt dry he blocked them out, post exposed and rushed them to press.
The press operator quickly set up the freshly made screens and began printing. Three hundred prints later the screens are breaking down again and I am boiling mad as I rush back to request another set of screens while I look up the telephone number to give Doctor Bob an assessment of his Aquasol TS emulsion. Doctor Bob and Walt successfully fixed my misunderstandings about emulsion exposure and more importantly the quality of light used to make the screens.
Well most of you are much calmer and nicer, but I wasn’t when I called Murakami. I had a Disney job due, a huge Disney job, the first we had ever done; an eight color discharge of the Beast with three foil colors of the rose in the domed glass cover, the shirts were to be given to all Disney attendees of the Academy Awards and then the rest put into Disney stores for sale the next day and I was shooting sets of screens non-stop, every 500 prints and I could barely shoot screens fast enough to keep up with the breakdowns on press. So I called and gave them an earful, amazingly I now work for them, why? Their products and knowledge solved my problems, and here’s how Doctor Bob and Walt enlightened me, pun intended. Your exposure unit controls your screen print destiny remember? The light an exposure unit emits can vary a great deal, from fluorescent tubes to an 8k Metal Halide. Just because the salesman said it would expose a screen, and it did sort of, gave you no clue to the quality of light it emitted. Sure it produced a screen, but how well did it expose the emulsion? Like car lots, you can buy a little four banger Focus or the fire breathing Shelby Mustang with 540 horses. Guess which one wins in a race?, no need to guess you know. So exposure units are the same, they either have the horsepower or they don’t. Long exposure time does not fix weak light or a light with limited spectral output. It all comes down to how the emulsion cross links and how complete and organized the cross linking is among the components in the emulsion. So to get perfect screens you need both: a very good exposure system, and a very good emulsion like Murakami, simply the best there is, I’ve used them all, this stuff really works and I say that as a production manager who printed for Disney, Nike, Walmart, Target, Quiksilver and Mossimo. Lets put it this way, I could fall asleep at night knowing the same set of screens printing a ten color discharge job on the graveyard shift would be printing fine in the morning and still print well on swing shift that afternoon and continue to print for several more days. Click here to continue reading the article: Exposure Lamp Comparison