In screenprinting, there are many variables that contribute to the success or failure of your project. Emulsion may be the most important variable, and it’s one of the easiest things to screw up. Of the half dozen-or-so emulsions I have tried, I have found Speedball Diazo Photo Emulsion to be the best, for me.
OK – so here is the basic, Award Winning* HOW-TO information you need to use SDPE successfully, everytime, every screen.
#1 – Coat the screen well. By that I mean, do a good job: it should be equally coated, without thick or thin spots. I personally do not use a safe light, but avoid direct sunlight. As soon as it is coated – get it into a dark place to dry. (I don’t think SDPE is photo sensitive when it’s wet, but don’t push your luck and use common sense when mixing, handling, and storing it.)
#2 – Let the emulsion dry completely before you expose it. This can mean 3-4 hours or overnight depending on humidity and air flow. If it’s not dry when you expose it, you are going to have big problems on washout.
#3 – Expose with a 300w bulb, approximately 12 inches from the screen for 12 to 16 minutes. That 5 minute range is the sweet spot. Depending on the bulb, there may be a focal point of light, aim that off the screen, so there is even light across the whole thing.
#4 – As soon as the exposure time is done, turn the exposure light off, and get the screeen under some cold water quickly. The cold water acts as a stop bath to prevent further light exposure. I generally do washout in regular light too, but avoid sunlight.
#5 – SDPE has a kind of yellow washoff at first, and then a bubbly washoff, and some blue/green washoff when the open areas come clear. You are going to want to make sure that not only do you get the open areas clear, but you wash off any blue/green bubbly stuff on both sides of the screen, and set the screen to dry horizontally. Otherwise, some of the time a kind of film will creep into the open area while it’s drying and block it. SDPE is easy to wash out, and needs very little pressure to do so. Too much pressure will blow your screen clean.
OK- if you have followed this advice, your screen should have come out great. If not, there may be one of 100 other things going wrong! Good luck on your next attempt.
3 things you want to keep in mind here, and some main reasons why SDPE works for me:
- I use water-based inks and do short runs.
- I have a home studio and hand pull my prints.
- I like to use an “easy” emuslion.
SDPE probably is not the right emulsion for you if you are using an autopress, solvent based or oil based inks, doing high-quantity runs, doing precise printing.
*I have not won any awards for this information.