Okay, so back in high school I did screenprinting all the time, and never had any problems with it.
Last summer I tried to make a screen to use for a music festival we were having, and every time I exposed it, all the emulsion washed out, leaving me with a blank screen again. I tried every day for a week, changing exposure times, and eventually ran out of time, decided I was cursed, and gave up.
So this year we're having another music festival, and I'm again attempting to make another screen. The first one I tried, the light source actually fell onto the screen, melting through the transparancy, and burning a hole in the screen. So I sighed, took the screen off, and started over from step one. I re-stretched the screen, applied the emulsion, and burned the image. As I washed it off, I was excited for a minute, because an image was actually appearing! However, a minute later, it was gone, all the emulsion was washed out.
I am using speedball diazo emulsion and a 150 watt light bulb (which I am guessing might be the problem, even thought the speedball instructions say to use it?). I am following all the speedball instructions exactly. I've decided for the future, that perhaps speedball is not my top choice, but until I use up this huge bottle of emulsion, I'm stuck with it.
So help? I need to do this ASAP, and don't have the time or money really to buy more equipment, or experiment for days with exposure times. Any hints on how I can do this with what I have? Thanks....
Of course it would be better to use a higher quality emulsion but many people use it with good results. I have used it years ago and if I remember it takes like an hour and fourty five minutes to expose a screen with a 150 watt bulb. It sounds like you just aren't exposing it for long enough, or you haven't mixed your emulsion properly.
I used this long ago
and as I remember as with even the better emulsions distance and time are important. I know it sucks to expose for such a long time only for it to not work. You can do a wedge step test
expose the screen at diferent times and slide a big piece of thick 11"x17" paper across the screen.
let me see if I can explain this so it makes sense. get the unexposed screen and the 11"x17" paper just to hold back light and let about 2" get exposed then slide the paper over 2" and keep doing this until you have 5 or 6 different exposures. Example: if you do this at 15 minuites apart and have 6 exposure then you will have a 15 min. 30 min. 45 min. 10 min and a 1:30 sec exposures.
If you think bumping it up to 30 min is better than go for it.
From what you discribe it sounds like not enough time or bad emulsion
hope this helps.
i am 100% in agreement with Motorcycle, it does take 1 hour and 45 minutes with a 150 watt bulb. i used HS emulsion for the first 5 years of printing with a 150 watt bulb and a tin pan reflector. 1 hour and 45 minutes with the bottom of the bulb 18 inches away from the image works every time.
Thanks everyone for your suggestions! Today I did it again, this time exposing it for an hour and 45 minutes, and I looked at it, and for whatever reason, thought it didn't look done, so left it for another hour and fifteen minutes, for a total of three hours.
After the three hours, I rinsed the screen, and I've ended up with a useable image (I think... it's still drying). There are some small parts that washed out that weren't supposed to, and some small areas that didn't wash out that were supposed to, but it's good enough for now. I think the image wasn't pressed tight enough to the screen, would that cause these minor problems? I'll use the sheet of glass instead of tape next time.
Again, thanks for the help!
A sheet of glass, some cardboard for the inside of the screen, pinch it together with your hands, and then stand holding it square to that big orange ball in the sky that hurts your eyes when you look at it.
I think they call it the sun.
World's best light bulb, and you don't have to buy it at Walmart.
Try it at a minute if you live near the northern border with Canuckia, shorten your time as you move closer to Equador.
ps - yes, the reason you got parts that wouldn't wash out was because the positive was not compressed tight to the emulsion.