Monday, October 08, 2012

Screen Printing 101

Multi color screen printing is the perfect technique for insanely bright prints. You can print multi color on sturdy paper with minimal equipment. T shirt multicolor printing requires a T-Shirt press. Manual rotary presses can be sourced used for about a thousand dollars.

You'll need wood (or metal) frames stretched with screen mesh (sized anywhere from 12” x 18” to 24” x36”), a piece of foam rubber to fit inside frame for exposure process, screen printing ink, squeegee, light sensitive emulsion, Light source (a halide work light is good), glass & weights to hold the glass down on the frame, a design on transparency or film (the design should be positive, not negative on the transparency). Thick illustration board, tape. Hinges for screen frame.
Two color print on an infant TShirt 

Source this stuff from art supply store or screen print supplier. Some items you'll get at a hardware store.

To start: Clean your stretched frame with mild soap, rinse and let dry. Coat screen with light sensitive emulsion (check instructions for light conditions appropriate to your emulsion). Coat both sides, scrape away excess emulsion. Dry overnight. Buy a pre-stretched screen, or put your screen fabric on the wooden frame, so taut that you can bounce a coin on it. You can use a staple gun, but take care not to rip the screen mesh with the staples.

Next: Put your art/design on a transparency, also known as a film positive. A separate transparency is necessary for each color in your design. Each color must be printed in opaque black on the transparency in order to burn a screen for that color. Create your design on your computer, and print the design on vellum or other heavy transparent paper on a laser printer. You can also send your graphic file to a film output service bureau for your film positive.

Expose your screen: Do this step in the dark. Check the instructions for your emulsion regarding exposure time. It may be necessary to do a test screen with graduated exposure times to hit the proper time.
Put your foam rubber on the floor or a table. Put your coated screen frame over it on the inside side of the frame (leaving the flat side of the frame pointing up). Put your transparency upside down on top of the screen. Put your piece of glass over the transparency, and weight it at the edges with books or some other heavy objects. If you have ink cans, they will do fine because they are heavy. Hang your light source about 18” above your screen and turn on for recommended exposure time. Develop your screen with warm water. Spray the screen until the image area is free of emulsion. If your screen doesn't develop, use more water pressure. Blot both sides with newspaper when done developing, to remove excess emulsion. If your emulsion comes off too easily, ruining your image, increase your exposure time.

Set up your registration guides. On your print table or surface, tape down two pieces of thick illustration board for the bottom and one side of the paper you will print on. Your piece of paper will fit into the guides exactly the same for all colors in your print. Mount your screen on screen printing hinge clamps so you print each piece exactly the same. Buy the clamps from a screen print supplier.

Step 5: Place you first piece of paper against your guides. Put ink in your screen and pull a stroke with the squeege. Lift frame to check your print. If the design did not completely print, pull another stroke.
Print the first color on all pieces of paper and let dry. For second and subsequent colors, register to the first color on one of your prints to insure tight regsigtration of colors throughout your print run.
Clean screens immediately when finished. You can do multiple prints. If your print smudges, try a finer screen mesh. If insufficient ink gets on the fabric, use thinner ink or a more open screen mesh.

Tip: Visit several screen print shops and observe the pros at work. Take a workshop to become familiar with the process.

Steve Lafler, Manx Media Custom Screen Printing
Call for a quote on your wholesale TShirt printing job 503-213-3671

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