Filed under: Screen Printing by ramune

When I decided to screen print the t-shirts for the Chicago Marathon I thought it would be a fun project that would not take more than a few days (including some testing). Unfortunately I made a silly mistake at the very beginning which caused some mild insanity and took up a ridiculous amount of time. I decided to go with photo emulsion because it was the only method that would allow me to do the design I wanted. Below is some boring info to give you an idea of what I went through. Mind you for each of these I had to put more emulsion on the screen, dry the screen completely and then wash it and dry it after exposing it.

Test 1: 250W Halogen Work Light positioned 12 inches from the screen, exposed for 10 minutes
Result: Screen looked exposed but emulsion washed off way too easily

Test 2: 250W Halogen Work Light positioned 12 inches from the screen, exposed in strips for 10/15/20/25/30/45 minutes
Result: Screen looked exposed but emulsion washed off way too easily

Test 3: 250W Halogen Work Light positioned 12 inches from screen, exposed in strips for 45/60/75 minutes
Result: Screen looked exposed but emulsion washed off way too easily

Test 4: 150W Clear Incandescent bulb with aluminum pie pan (like directions recommend), exposed for 45 minutes
Results: Screen looked exposed but emulsion washed off way too easily

Test 5: 150 W Clear Incandescent bulb with aluminum pie pan (like directions recommend), exposed for 45 minutes, washed really really carefully
Results: Screen printed fine but there were areas where the ink bled through where it wasn’t supposed to

After switching bulbs and adjusting exposure times I finally decided that something was definitely wrong with my emulsion. It seemed to be working fine (I could see that my design was showing up) but it would always wash away far too easily, so I bought new emulsion and made sure it was completely mixed (ALL of the sensitizer has to be mixed into the emulsion or else . . .). Sure enough everything worked! If only I had realized that was the issue from the beginning, it would have saved me days of experimenting and brain scratching. Unfortunately I think I overexposed my screens because I was never able to fully get the emulsion off the screens when I wanted to clean them completely. I need to look into other options so I can reuse the screens. Anyway, here are some photos of the (successful) process.

Exposing the screen with the new and well mixed photo emulsion (rig consists of a tripod, 150W clear incandescent bulb, aluminum pie pan)

Seven minutes into exposing the screen I noticed that I had mistakenly typed MMVII instead of MMVIII! My guess is no one would have actually noticed but I ran to my computer and printed out an extra “I” and very carefully placed it on top of the screen. It messed up the exposure a wee bit but I was able to cover it up easily enough before printing.

Hooray! The photo emulsion worked!

Printing on one of 26 shirts

Success!