screen printing > Screen Making

do screens have a shelf life?

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Evo:
Review every step.

Degreasing
Drying
Coating
Drying
Exposure
Post exposure
Press use
Reclaim process

I've seen stupid simple things such as a swift change in humidity throw a screen room into a tailspin.

Evo:

--- Quote from: balloonguy on June 25, 2024, 05:31:09 PM ---I went from a thermal film from oyo to epson inkjet.

--- End quote ---

Did you carefully re-calibrate your exposure times? Some films can have an big effect on exposure. The clarity and transmissivity of films can vary wildly and there is ink receptive coatings on inkjet film. It's possible you need a much longer exposure to have the proper amount of UV energy to punch through the new film. The detail you want might still be there and the screens are holding up ok on press, (for now) but inadequate exposure might be locking the emulsion up.

I would do a thorough step-wedge test once the new lamp is installed.

scott316:
What exposure unit do you have ? Has your times changed ? If emulsion is not exposed correctly and chemicals hit the emulsion it can lock it in.

balloonguy:
Sorry to take so long getting back to this…
I checked a lot factors. After getting a new bulb I tried to do a step wedge test ranging from 5% of expected time to 400% of expected time. I never got a good exposure and still had issues with the emulsion locking. I emailed the manufacturer and the reply was pretty worthless. About a week after emailing they replied with my batch number was the last of 2023 and that they had no other complaints or issues. I tried a few other brands and all the results were pretty good. I ended up with ulano orange. The step wedge came in just slightly over what I calculated from the spec sheet. I am fairly certain that the issue was a bad batch of emulsion. I damaged a lot of screens including 4 more while testing with the new bulb. Sometimes the obvious answer is the correct answer.
As always I appreciate the response and help I get from you guys.
THANK YOU ALL!

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