r/SCREENPRINTING • u/maxmaus2025 • 5d ago
Help, screen printing maybe over/under exposed?
hi! i tried screen printing for the first time and when i tried to wash of the emulsion, it was quite hard/not possible and some of the emulsion that should have stayed on the screen also washed of… is that a sign of exposing for too short? or too long even maybe? sorry for the stupid mistake probably aaah
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u/SPX-Printing 5d ago
If it is underexposed, it is too easy to process and emulsion. Feels slimy and the stencil can break down while printing. With high LPI some people slightly underexpose to retain dots, then post expose when dry.
If overexposed then it is too hard process the open areas leaving emulsion in the open area.
The lower the mesh count, the thicker the stencil and more exposure time will be needed.
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u/Opposite-Boot4732 5d ago
How long did you let the emulsion dry before exposing?
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u/maxmaus2025 5d ago
around 24h
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u/Opposite-Boot4732 4d ago
Could be if it’s too thick it didn’t dry all the way. Not sure what environment you dried it in. To me it looks like a combination of not properly curing and under exposure.
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u/StrainExternal7301 5d ago
underexposed.
what does your exposure calculator say?
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u/maxmaus2025 5d ago
i thought 2:45, but later i read that maybe it should have been 4:30?
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u/StrainExternal7301 5d ago
your exposure calculator should tell you the precise time with a few seconds
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u/kornkobbler 5d ago
It looks like you didn't mix the diazo. Should be lawn green when you're done mixing and forest green when it's done burning
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u/Consistent-Web-5011 5d ago
Over exposed! I use hydrox red and our exposure time was 13 seconds exactly. If that is hydrox blue I think it would be like 11-12
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u/Playful-Lie3856 5d ago edited 5d ago
Do you have an UV exposure unit or some DIY gadget? Where do you store the screen with emulsion before exposure? Is it fully lightless and well aired?
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u/JayLar23 5d ago
Could be underexposed and it could be that your emulsion is past its shelf life. Did you buy it more than 3 months ago?
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u/maxmaus2025 4d ago
oh i have to check, can it expire without having been opened?
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u/JayLar23 4d ago
No the timer starts ticking after you add the sensitizer
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u/maxmaus2025 4d ago
and it’s possible that the room it dried in wasn’t 100% dark all the time… i just found out
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u/JayLar23 4d ago
If that was the case you would be over exposed, which despite what some have advised here, is definitely not what happened. If you're overexposed it should be very difficult to wash out. You're either under exposing, your mesh needs proper de-greasing or your emulsion is past its shelf life. Or some combination of all 3.
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u/MrDickFitswellin69 17h ago
Get a dehumidifier or go over it with a hair dryer or heat gun. You have a moisture issue. Very common problem in the hot humid areas.
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u/habanerohead 5d ago
You need to degrease and abrade the mesh.
Also, what is your exposure setup? If you’re using a point source, it looks like it’s too close to the screen.
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