Screen printing is a printing process where an image is created on a framed mesh screen by exposing a photosensitive glue-like emulsion all around the image. A plastic transparency, or tracing paper with the desired image opaquely printed on it, is the medium used to selectively expose the screen. The portion of the screen that is not exposed to light is cleaned to reveal the open, porous screen. This part of the screen allows ink to flow through, thereby reproducing the image onto fabric, paper or wood. The process is often called "silk screen," although the screen material is not silk.
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Things you need
- Wooden frame
- Screen material (found at art supply stores)
- Staple gun
- Degreasing cleaner
- Photo emulsion
- Squeegee or flat rubber blade
- Pie tin
- Lamp cord
- 150-watt light bulb
- Round screw hook
- Black construction paper
- Transparency of desired image
- Piece of glass to fit inside frame
- Measuring stick
- Garden hose
- Hinge clamps
- Screen printing ink
- Item to be printed
Find a frame. The screen printing frame should be several inches larger in height and width than the image you want to print. An old wooden picture frame works well.
Lay the frame horizontally on a flat surface.
Use a staple gun to attach screen material to the upward-facing edge of the frame. The material should be pulled as tight as possible. The tighter the screen, the better the print.
Clean the screen material with a degreasing agent and rinse. This removes any chemicals left over from the screen material manufacturer.
Make a Screen
Purchase an emulsion kit and sensitiser. Mix the emulsion with the sensitiser.
In a dim room, place the screen face up on a covered surface and pour a thin line of emulsion on the top of the screen.
Use the squeegee or a flat rubber blade to spread the emulsion downward, covering the screen as thoroughly as possible.
Lift the screen and turn to the other side. Move the rubber blade upwards to spread any emulsion that went through the screen material.
Lay the screen face up once again and pour a thin line of emulsion at the bottom of the screen. Use the rubber blade to move the emulsion up to cover any portions of the screen that have not been coated.
Lift and flip the screen over to spread the emulsion on the other side. Repeat the application of emulsion on each side until the entire screen is coated.
Scrape any excess emulsion back into the emulsion bottle.
Place the screen in a dark place to dry for about an hour. When it's ready, the screen will be dry to the touch.
Place unused emulsion in the refrigerator. It will last four months at that temperature.
Find a flat surface where the screen can be exposed. The surface should either be in a dark room or in a room that is dark at night.
Poke a hole in a pie tin and secure it to the bulb-socket side of the lamp cord.
Insert a 150-watt clear bulb in the lamp cord socket.
Screw a rounded hook screw to the ceiling directly above the exposure surface.
Plug the cord in and run it through the hook. Clamp the cord to itself so that it hangs above the exposure surface.
Set Up the Exposure Unit
In a dark environment, remove the screen from its drying place.
Lay the frame under the exposure lamp, screen-side down on a piece of black paper. Do not turn the lamp on yet or otherwise expose the screen to light. Use a flashlight to find your way around.
Place the transparency or tracing paper with your image on the screen and secure by placing a clean piece of glass over it. The glass must be larger than the image but smaller than the screen. If the screen was made with an old picture frame, use the glass that came with the frame.
Measure the height of the lamp specified on the emulsion instructions and reclamp into place. It is usually about 12 to 15 inches.
Turn on the lamp for the amount of time specified on the emulsion instructions. It is usually about 30 to 45 minutes.
If the screen is in a warm place, set a fan beside it to remove any heat build-up from the bulb. Heat will expose the emulsion as well as light.
When the exposure time is up, turn off the lamp and quickly spray the screen with a garden hose to remove the unexposed emulsion. This must be done at night to avoid exposing the screen image. You may also use a spray bottle, although it will take much longer to clear the unexposed emulsion.
Allow the screen to dry. You should be able to see through the screen completely in the area of the image. If all of the emulsion comes off, it was not exposed enough. If no emulsion comes off, it was exposed too much. This is the most delicate part of the entire screen printing process.
Expose the Screen
Now for the best part: printing! Secure the screen on a flat surface. You may use hinge clamps to allow the screen to be lifted up or clamp the screen to the flat surface.
Place the material to be printed, such as a T-shirt, under the screen.
Press the screen firmly to the material. Pour a thin line of ink on one end of the screen and spread with the thin rubber blade.
Lift the screen, and your image will be printed on the material.
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