How does screen printing work?
(The following paragraph is from http://www.printmaker.co.uk/sprnt.html)
The equivalent of the printing plate for the screen printer is the SCREEN -
a wooden or aluminium frame with a fine nylon MESH stretched over it. The MESH
is coated with a light sensitive emulsion or film, which - when dry - will block
the holes in the mesh. The image that needs to be printed is output to film
either by camera or image-setter. This film positive and the mesh on the screen
are sandwiched together and exposed to ultra-violet light in a device called
a print-down frame. The screen is then washed with a jet of water which washes
away all the light sensitive emulsion that has not been hardened by the ultra-violet
light. This leaves you with an open stencil which corresponds exactly to the
image that was supplied on the film. Now the screen is fitted on the press and
is hinged so it can be raised and lowered. The substrate to be printed is placed
in position under the screen and ink is placed on the top side of the screen,
(the frame acts also as wall to contain the ink ). A rubber blade gripped in
a wooden or metal handle called a SQUEEGEE (not unlike a giant wind-screen wiper)
is pulled across the top of the screen; it pushes the ink through the mesh onto
the surface of the substrate you are printing. To repeat the process the squeegee
floods the screen again with a return stroke before printing the next impression.
Thanks for the facilities in Caltech, we can do silk-printing at the silk-printing
room in SAC (Room Art 22).
Take the following steps:
- Several days before the actual work: Get the key to the room (ususally a
south master key can be obtained from undergraduate students)
- At least one day before the printing: make a mesh coated emulsion.
- Get a wooden frame (if necessary, make one)
- Get a nylon/silk gauze, use the gauze to cover the wooden frame; use
rope to fix the gauze tightly -- the gauze should be completely lengthen
and flat (as flat as possible)
- Get a emulsion film (the film is a plastic film with one side coated
with green emulsion), cover the gauze with the film. The coated side should
touch the gauze.
- Wet the gauze with water, make sure that the gauze and the film are
- Wait for at least one day: due to the water, the green emulsion will
stick to the gauze -- the tighter the gauze and the film, the better
- Get the T-shirts. There is a T-shirt factory outlet on Rosemead, close to
the intersection of Colorado and Rosemead, on the east side of the street.
I bought some from there last summer. The address is 50, S. Rosemead Blvd,
Pasadena. #:585-8810. You can find more infomation on the yellow page.
- Design the pattern, print it on a transparency.
- On the day of work:
- Tear the plastic film off the gauze -- the green emulsion should now
stick with the gauze and only the transparent plastic film will be tear
off (Otherwise, mission failed)
- Put the transparency (with pattern) on the gauze (Make sure you put
the transparency in the correct direction)
- Put the frame (with gauze and transparency) to onto the ultra-violet
light machine (the lowest layer is the transparency, then the gauze with
emulsion, then the frame)
- Start the machine with a exposure time of 85sec (as default)
- Now you can see the green emulsion changed a little bit on the places
covered by the patten on the transparency; take the transparency away
-- now the transparency finishes its job.
- submerge the frame (with gauze) into water for one or two minutes.
- Use the water jet to spray water (with high presure) to the gauze (from
the side without emulsion to the side with emulsion). You can see the
emulsion turned solid for the places that are not covered by the pattern.
The parts covered by the pattern will pop out due to the water pressure.
- keep on spraying for a few minutes, try to use your thumb to scrape
the emulsion (Do not your nail, it may cut the emulsion) If you feel the
emulsion is off the gauze, go to the next step
- Use the water jet to spray from the side with emulsion to the side without
emulsion, with different angles. You can see the emulsion is getting off
the gauze for the parts that were covered by the pattern.
- Use thumb to speedup the process.
- Finally, you will get a gauze on the frame, with all the uncovered parts
covered by solid emulsion and all the covered parts hollowed. (the paints
can go through the holes)
- Dry the frame, use tapes to fix all the unwanted holes and secure the
- Put the frame(s) on the printing stand, make sure that the frame will closely
touch the t-shirt when it is pressed down.
- Put the oil into the frame, put the T shirt on the platform, press the frame
down on the T shirt, and brush the oil. -- You get one T-shirt with painted
- Put the T-shirt on the dryer and run the dryer.
- You get a painted T-shirt.
Step 1~6 are the critical parts. But they just need to be done once for each
pattern. Step 7 and 8 should be repeated as long as you want to have more T-shirts.