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Here's the deal. My exposure unit is home made. It consist of 12 40 watts, 4ft. long, fluorescent unfiltered black light bulbs. On top of it there a 40in x 54in 1/4 thick completely clear glass (no treatments of any kind on the glass). The wood I used for the walls are 12 inch tall so I estimate that the bulbs are 7 to 8 inches far form the glass.

I use the Saatichem Textile PV photopolymer emulsion and I coat my 110 mesh screens one time on each side. Properly coated with a coater and properly dried in an horizontal rack.
I print my transparencies on an Epson Stylus 1400. I use standard inkjet transparencies but I print two copies of the design (in the best quality possible) and place them together to make a dense positive.

So... the dilemma is that I've done every step wedge imaginable to man. And it seem that my screens over expose if I give them more than 40 seconds of light. I then used 35 seconds and 30 seconds. When I try to wash out the design it doesnt matter if I use a pressure washer or a standard hose the design proves so hard to wash out it will sooner or later blow out of the screen. I did a step wedge and 5 seconds, 10 seconds and 15, wash out, 20 and 25 are under exposed, 30, 35, and 40 seem right and the rest over exposes. The thing is that it is a really small design about 3 inches wide 2 inches tall but when I expose a very big design 40 seconds prove just right. Is it possible that the emulsion will shoot a lot faster than 30 seconds even though the step wedge washes out? I'm kind of new to screen printing and coming from dual cure which exposed for me in 5 to 7 minutes seems kind of impossible that the emulsion will shoot at 15,20 or 25 seconds. Any thoughts or recommendations on this? Keep in mind that the positive is making the right contact with the emulsion. I'm applying over 40 to 50 pounds of pressure on top of the design.

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Hi Nachthymn

I admire your thoroughness and attention to your variable controls.

Emulsion speed is important, but faster formulas aren't always the best for all exposure systems.
If you find that your combination of stencil and lamps have you at a +/- 8 second window for under/over-exposure,
a slower speed emulsion will give you more elbow room for image quality adjustment.
InkedApparel hints at this recommending that you make your exposure system less intense.

Note that the double layer of film will scatter light around the defining edges of your image
and make it more difficult to relate fine resolution to proper exposure times.
See if you can retest with a single layer film with sufficient density.

Happy trails!

P.S.- Have you shot a graduated half-tone bar test yet?
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