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Discussion Starter #1
Ok, I did a test on a 156 and a 200 mesh screen from 5-12 minutes. I swear to god each minute came out the same- except 11 and 12 minutes on the 156 screen.

So which exposure "minute" do I choose? Something in the middle like 7 or 8? Thanks.


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If you are using a diazo sensitized emulsion, increased exposure will "bleach" the 'yellowish' diazo and return the emulsion to the color it was before you sensitized it. If it's an SBQ emulsion - there won't be any color change -because there is no diazo.

Nothing points to 7-8. You need to look for extremes - for changes. From your report, there is change between 10 and 11.

Did the 5 minute dissolve? If not, you MAY need to lower your aim so you can find a range where there is color change.

With your experimenting first find where the stencil starts to adhere to the mesh - for you that could be 5 minutes, so 2, or, 3 or 4 minutes will dissolve with water. If that's so- 10 minutes is overkill and wasted energy.

If you're printing water-base ink, you MUST completely cure the stencil so it will survive printing and should be using a dual-cure or diazo sensitized emulsion. If you're printing plastisol, it harmless and won't hurt anything, so it's not so important.

I know you're in your first days, and it's the weekend. When you can, quietly discuss with the person who sold you an exposure unit - Why they forgot to include a US$10 Stouffer T-2115 21 step gray scale that simulates 21 different exposures each time so you could measure exposure. This is a standard photographic darkroom test positive that's been used since the 1930's. They're supposed to know better - you aren't. Once you get one you'll know how many hours you could have saved.

Properly used it should last a lifetime, so I want you to put one on every screen you expose for the rest of your life. It's visual feedback you exposed the stencil properly.
 

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Discussion Starter #4
I don't really get what Richards saying. I made my exposure unit with (2) 1000 watt lights.

And Dave, at 11 and 12 minutes the emulsion didn't wash out so I'm guessing that was too over exposed. I settled on :

110- 10 mins
156- 9 mins
200- 8 mins
230- 7 mins

It's in the middle as far as I can see.


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