are you using a bulb for exposure? it looks like the center is overexposed... let me know what type of emulsion, how long you exposed for and what exposure method you are using and I may be able to help.
are you using a bulb for exposure? it looks like the center is overexposed... let me know what type of emulsion, how long you exposed for and what exposure method you are using and I may be able to help.
Yes I'm using a 150w bulb with a 8.5" reflector 12 inches above the screen for 10 minutes and 30 seconds. It's diazo emulsion I got with a speedball kit. I'm using a sheet of glass that is 1cm thick on top of the screen. This is my first time trying it and I'm already fairly frustrated.
well by looking at it I would definitely say overexposure is your problem.. does the kit come with instructions? its been ages since I've dealt with speedball stuff so its hard to remember all the details... it looks as if the bulb is too close to the screen or you exposed for too long (there are a lot of factors when if comes to exposure)... hopefully your kit came with some reclaimer so you can clear the screen and try again
If you are that down and dirty and don't have the right equipment I can suggest two things. One the glass needs to be "photoclear" your typical "soda glass" causes too much difussion. Almost any glass company sells it. You wil have waaaay better results. If you can't get a piece that's OK use what you got.
Rather than using a crummy light source... use the SUN! You have to be fast: Have a piece of foam thicker than the screen wood ie 3 to 4 inches thick of foam. Have the coated screen with the artwork attached to it in a black garbage bag. Find a level spot, put the foam on the ground, whip out the screen, put it over the foam, put the glass over it and expose. I don't know what kind of emulsion you have but a guess would be about a minute/minute and a half. When done exposing just throw the bag over the screen, get another bag and slip it all in keeping the sun out. It even works on grey days no problem. I had to do this when my shop burned down ( along with 20 other businesses in the building). Long story but you do what you gotta do! Good luck.
Oh yeah... by the by if you don't have emulsion remover you can use bleach. Takes about 20 minutes to soften the emulsion but it WILL work.
Last edited by Powakai; August 21st, 2007 at 04:47 PM.
thanks a lot, I got it to work but i had to rais the light andmove it around so it wouldnt burn to hot in one spot but it's good enough for what i need it for. I would have used the sun but it's been raining for 2 days and the shirts need to be done by saturday. Thanks again for the advice.
If some areas are coming out fine and not others I would have to agree and say it's your light source. I have also just started screen printing and found it to be a pain in the ***. My screens never came out because the ink on my films didn't block enough uv light. I made 4 screens before finally scrubbing one of the screens with a toothbrush to reveal some of the areas. It worked but I lost some detail in the edges. Your screen can probably be salvaged.
Now I'm looking into get RIP (Raster image processor) software so the ink is more dense and so I can do halftones, and getting an ink like FastINK for my epson r1800 and waterproof film positives so I get crisp screens.
Have you tried spraying your positives with "Acrylic Fixative"? You can get spray fix at any art store. It remelts the toner and makes it 30% darker. Some fixatives have UV block in them so you don't want those.
I just print out vellum on a large format laser printer, spray on the fix let it dry and shoot. I do a lot of halftone work and consistantly get 5% dots and higher at 65 lpi. My light source is a 5000 watt metal halide UV gas bulb and I use a poly-cop. As with anything the right tools makes all the difference.
You're only exposing your screen for 10 minutes and 30 seconds? I ask because I have a similar set-up, but exposed mine screen at 14 inches for 92 minutes (per the Speedball instructions), and my screen is overexposed too.
Anyone have any idea how much I should expose it for?
(150 w bulb, with 8.5" reflector using SpeedBall Diazo emulsion. Any help would be appreciated.
thanks,
Craig
P.S. I could turn the underline off for some reason.
All exposure questions are answered with a stepped exposure test which is essential to any screen maker.
You do a series of 'stepped' exposures on the same screen, then JUDGE the proper amount of exposure.
Thats what I did. It was the bulb that was the problem. The light and heat was more focused in the center so I had to keep moving the screen while exposing. It worked well enough but I need to get a new light.
Sprayaway makes a product called Toner Aide that works much better than an art store fixative, not all vendors carry it so you may have to shop around a little bit, try it you'll be glad you did although it smells awful...
Sprayaway makes a product called Toner Aide that works much better than an art store fixative ...
Toner Aide and Krylon Fixative ares strong chemical solvents (acetone & xylene), that is used to MELT the plastic laser toner on a laser positive for increased opacity - like melting grated cheese on a pizza it will close all holes that might let light through.
Alas, a strong solvent will to little to increase water-based ink opacity on ink jet film.
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How are you measuring? Ulano Technical Product Manager - NYC
Emulsion problem... 
