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Screens.

Postby CPM » Sat Dec 07, 2013 7:29 pm

I have been doing a little screen printing for the last several years. I use direct emulsion sheets and, for reasons too many to go into here, I have recently changed the supplier of my emulsion. I am using 50 micron emulsion applied to 110 mesh screens, and I am having trouble keeping the emulsion on the screen during washout after exposing the image.
Previously, I was using Ulano 38 micron roll material instead of the cut sheets. My exposure light box has only regular florescent tubes and not the 'black' ultraviolet lights. With the regular florescent lights, my exposure time for the Ulano emulsion was 12 minutes. I have tried exposing at various times between 12 and 20 minutes with the new emulsion sheets, but when I try to wash out the exposed image, the rest of the emulsion is blowing off the screen before the image is completely washed out.
My process for applying the emulsion is as recommended by the manufacturer, and is, incidentally, the same process as I have been using with the old emulsion. Lots of people are obviously using these pre-cut sheets successfully, so I can't blame the material. As much as I hate to think it, it is something that I am, or am not doing.
I can only think that it has something to do with exposure times, but I don't know if I am exposing my screens too little, or too much.
As a matter of interest, the recommended exposure times with the new emulsion using 'black' light, is 3 minutes.
If any one can help me with this very annoying problem, I would be very grateful.
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Re: Screens.

Postby d fleming » Mon Dec 09, 2013 2:08 pm

Switch to unfiltered uv tubes and do a step wedge test.3-5 minutes should get you a pinpoint shot. A search here will get you to how to do one. Mesh that isn't properly cleaned and prepped could be the culprit as well.
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