I'm having some problems exposing my screens. When I've finished exposing them I can see the image burnt to the emulsion the way it should. When it comes time to wash away the emulsion after exposure it'll go alright for a while, the parts that need washing away will start to go, a little reluctantly perhaps; but they'll disappear while the rest of the emulsion looks pretty solid on the screen; but then the rest of the screen will start washing away too. The emulsion on the screen starts getting very slimy and soapy when water touches it.
I'm using a 500W lamp that I bought from Walmart for $12. There used to be a thick glass cover in front of it, which was blocking some of the UV light, so I've removed that. I've got the lamp 15" away from the screen, with a sheet of glass holding the transparencies against the screen. I'm using 2 inkjet transparencies stacked on top of each other. I've been exposing it anywhere from between 12 minutes to 1 hour and I've had no luck.
I believe the emulsion I'm using is Diazo. It came with the screen printing set that I bought.
I've got no idea what's going wrong; if it's the lamp or the emulsion. I heard soapy, slimy emulsion could be caused by under-exposure. I'm guessing they included some poor quality emulsion in the kit and that I'm going to have to throw it away and buy some more, but I thought I'd ask for help first.
Can't speak to the quality of the emulsion but that sounds like you're not getting enough light onto the screen during exposure. Do a few searches for under exposure and I'm sure you'll find something worthwhile, this has been discussed plenty of times in the past. Once I got sick of playing around with that stuff I threw out the speedball emulsion and got a exposure calculator. Saved me tons of frustration.
if you are burning for 1 hr and not getting a decent stencil, I would start with some good emulsion. it only lasts for a few months, how old was the kit?
there's 20 other things it may be (search the threads, this exact question has been dealt with over and over) but it starts with good fresh emulsion, a decent light source, and an even thin coating with a scoop coater. If you don't have those things happening, good luck
The emulsion sat around in a cold dark place for about six months after I bought it, but I hadn't added the sensitizer to it. I was told it would last for quite some time before it's mixed. I did take it on a plane with me so I wonder if maybe the x-rays, or the cold air in the cargo hold screwed it up or something.
I guess I'll have to just pay for some new emulsion and see how that works out. I was hoping to put it off until I could find out exactly what the problem is, just in case I end up with two big tubs of emulsion I can't use.