I'm new to this forum and to the whole screen printing process. Just looking over some of the older posts I'm in awe at how much I don't know about screen printing. Let me first tell you that I'm using Diazo photo emulsion, I've been hearing good things about Ulano so once I run out of this stuff I'll move to that. I'm also using some 10XX screen fabric and a picture frame for the frame itself.
My first issue I ran into was when drying the emulsion, a few small drips showed up. I've heard that I might have used too much emulsion and that using a fan decreases the likelyhood that this would happen. Any comments?
Right now I don't have a light source so I used the sun today. I'm also using a transparency stencil. I had it out there in the morning around 9 am for about 25 minutes. That seems to be too long. When I went to wash out the screen, my graphic was green colored, while the exposed emulsion was blue.
The emulsion that wasn't exposed was not washing out. After much time, I could start to feel a few places were the emulsion was off. The screen is still unusable because 95% of the unexposed emulsion would not come off.
So ultimately my question is, did I over expose the emulsion, causing even the emulsion behind my graphic to get exposed as well?
How bad would it be to only coat the front of the frame with emulsion?
One more note, I'm tiny scale, just a few t-shirts here and there, nothing over 20 shirts probably.
the suns rays have very powerful uv light, I would try exposing for about 5 minutes next time, and make sure your transparency is opaque enough that no light can get through, double stack if you need to. with the sun as a light source it will be trial and error at first.
also, when you dry your screen after coating with emulsion, dont stand it up to dry, lay it flat, shirt side down, riased off the ground or table by putting peices of wood or whatever under each side of the frame, this should eliminate runs in the emulsion.
its hard to say, sounds like your using a home made screen, and i dont know how your coating your screen so I dont know how thick you applications are. you'd have to try and see if it works.
with a normal screen using a scoop coater I coat both sides.
I'm using a 10 X 14 picture frame as the screen. I'm using a 9" red baron squeegee to put the emulsion on. I was able to poor the emulsion on the squeegee, place the squeegee on the frame, and move the squeegee up in a constant motion. I think it was thin enough, next time I'll move a little faster. Thanks for your help though. I know it's a lot of practice so I'll keep at it.
how long has it been since you mixed the diazo? they have a much smaller shelf life (2-3 months) where as pre-sensitized have (8mon- 1 yr).
Also, are you coating in a dark room? If you're coating in the light, you're already starting to expose.
Lastly, how long do you let the emulsion dry? I let my screens coated dry overnight to make sure they are dried all the way to the mesh, not just touch safe.
Just a few hints and questions for you to check out.
p.s. I love ulano emulsions, so that's a personal good choice!
I mixed the diazo actually only 5 minutes before I put the emulsion on. I coated it late in the evening, so I don't think it was exposed that much. I let the diazo dry over night as well. Thanks for the help though. Also, where do you get your Ulano, online somewhere?
Emulsion Not Washing Out 
