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Emulsion Issues

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Emulsion Issues

Postby SteveTad » Sun Mar 28, 2010 5:29 pm

I thought I would save my question for this particular thread. Anyways, I am using ProChem DXP Pink Dualcurediazo Emulsion. The problem I am having is this: I would coat my emulsion once on each side of the screen, wait for it to dry and then burn the image onto the screen using my PVC Exposure unit. The company I bought my equipment from said I should take off the UV Glass Filter, which I did, and burn the image onto the screen for about 12min, which I also did. Took the screen to washout and not only did the stencil washout, but the access emulsion around it started to blowout which would cause me problems when I would go out to print. Is there anything I could be doing wrong in this process? Over exposing? Under exposing? I have no idea. Any suggestions on anything I could be doing wrong and how to correct it would be greatly appreciated. Thanks.
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Re: Emulsion Issues

Postby d fleming » Mon Mar 29, 2010 11:32 am

Taking for granted that there is not a problem with the emulsion itself it sounds under exposed or a not so clean screen. Have you done a step wedge test to determine the proper exposure time with your setup?
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Re: Emulsion Issues

Postby SteveTad » Mon Mar 29, 2010 3:03 pm

I know you have probably gone through this before, cause I have read some of the past threads on this board, but what is a step wedge test?
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Re: Emulsion Issues

Postby d fleming » Mon Mar 29, 2010 4:32 pm

Here you go, I used the search feature at top of page to find one of my old posts.

A step wedge test is simply exposing the screen at different time intervals. Cover 75% (approx) of screen with cardboard to block light, expose. After a few minutes, move the cardboard to expose more screen, continue in this fashion until whole screen has been exposed. This should give you some indication at washout as to which direction your time needs to go, more or less. There shpould be a product sheet with every purchase of emulsion or online to tell you about a step wedge, light distance, etc., for your product. For instance...

http://www.ulano.com/TechData/RLX.tds.pdf

Here is the tech sheet for the rlx I use for t-s and coro as well as psa vinyl.
Don't know about the emulsion you are using but I have been using rlx for many years with constant results.
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Re: Emulsion Issues

Postby SteveTad » Mon Mar 29, 2010 10:32 pm

that actually sounds familuar, kinda like what you would do in film photography when you want to expose B&W Pictures to see what F-Stop works better and for how long. Ive actually done that, but not in screen printing, but I will try that. Just one question though, would you reccomend doing that with a test image?
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Re: Emulsion Issues

Postby d fleming » Mon Apr 12, 2010 11:05 am

Test image would be fine.
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