Shirty/HOWTO

Notes from screen print test session 23.06.09

• Material bought from Wöco:
  • Screen with frame
  • Emulsion
  • Sensitizer
  • Paint
  • "Squeegee"
  • Cleaning agent to clean away hardened emulsion
• Sensitize emulsion:
  • Fill up the small sensitizer bottle with water
  • Add to the box with emulsion
  • Stir well
• Coat screen with emulsion
  • Do this away from bright light or sunlight
  • Use the "squeegee" to coat the screen with emulsion
  • Do this from both sides repeatedly to get an even coverage and an even surface as a result
• Dry the coated screen (this will taka 30-60 minutes)
  • Place horizontally in a _dark_ room
  • To speed up, use a fan (occationally using a hairdryer might also help)
• Prepare the design
  • Design a positive 1-color bitmap image (i.e. what you see is where the ink goes)
  • Print on a transparent foil using as dense ink as possible
  • Our printout was not very dense due to a broken/out-of-ink printer
• Expose the screen
  • Place the screen with the flat side down on a horizontal surface
  • Place the printed transparent foil onto the screen
  • Mount a UV lamp lighting downwards with ca. 1 meter distance
  • We used the IR+UV lamp from the Chemielabor. Note! The UV lamp won't work lighting downwards, for some reason. Alternative setup: tape the transparent foil to the screen with _transparent_ tape. Cover the backside with something non-reflective.
  • Exposure time: 15-20 minutes. This depends on the thickness of the emulsion, too short and the opaque areas have not hardened, too long and thin lines in your design bleed together.
• Clean away the non-hardened emulsion
  • Use warm/hot water with as much pressure as you can get from a shower head
  • Since our print wasn't very dense, this had an effect on the exposure: Less well-covered areas had clear half-hardened emulsion. These areas, in addition to areas with small details were a lot harder to wash away. Using a dishwashing brush helped a lot.
  • If some emulsion doesn't come off, use a small _plastic_ tool (e.g. a reprapped palm stylus) to _carefully_ scrape away the remaining emulsion.
  • Now, let the screen dry. Shouldn't take long.
• Apply paint
  • Line up a bit of paint just outside the motive
  • Using the squeegee, carefully drag the paint over the motive so the whole motive is covered with paint
  • If it's not fully covered, drag it back again
  • Using a bit more pressure, drag the squeegee once over the entire motive
  • Carefully lift the screen from the motive
  • Every once in a while, clean away dried paint from the screen with water
• Drying
  • Using a hair dryer, lightly dry the fabric
  • At this point, to make the print permanent, an iron should be used on the fabric. We didn't have one available, so who knows what will happen now..