Wednesday, June 22, 2011

How to Screen Print T-Shirts

Screen Printing is an amazing technology. You can print intense, bright ink on just about anything with it. Of course it's great for printing T-Shirts. With a trip to the art supply and hardware stores, you can set up to print in short order. You can also source screen printing supplies on the web, or from wholesale screen printing suppliers. Here is as link to one other online supplier.

Let's assume you've already created a design that exists as a digital file. You mighta used Photoshop or even word, but it's done, right? For first timers, it is best to start with a design for printing in just one color of ink.

Get some clear vellum paper and print out your design on it. Use a laser printer for best results. The print is a film positive, used to put the image on a screen. The print must be opaque to make a screen. If it's not opaque, draw on the back with a black marker or brush and ink.

Buy a ready made screen print frame, stretched with synthetic mesh fabric. You can stretch your own screen fabric if you prefer. Choose a mesh count that is versatile. For general T-Shirt printing, start with a 110 - 180 mesh. Anything in that range should do. T-Shirt printers use mesh counts from 80 to 350, but a mesh of about 150 is the most versatile.
Clean the screen print frame with soapy water and rinse completely. Let it dry overnight.

Purchase some photo emulsion that can be used with water based ink. The emulsion must be sensitized before use. Mix the sensitiser as per the instructions that come with it. Do this in the dark!

Coat both sides of the screen with the emulsion. Use a stiff piece of illustration board or a squeegee. You can also buy a metal screen coating tool, a trough that you pour emulsion in, then coat the screen with. Go for an opaque, thin layer of emulsion. Remove any excess drippy emulsion with a stroke or two on each side. Put the screen in a dark place, face down. Let it dry overnight.

Check out the image above, how to burn a screen. You will use the film positive to put the image on a screen. This step must be done in a darkened room, with running warm water available. Cut a piece of foam rubber to fit inside your screen print frame. Place the piece of foam rubber on a flat surface. Place the screen print frame face down over the foam. Put the film positive face down and centered on the back of the screen. A piece of heavy glass goes on top of the film, frame and foam. Quarter inch glass is great for this as it holds the film positive in close contact with the screen print frame.
Hang a halide light about 15 - 18 inches over the film positive. Turn it on for about five to eight minutes. Exposure time depends on your emulsion. Check the instructions that came with the it for recommendations on exposure time. Often some trial and error is necessary.
If your design washes out, increase your exposure time. If it clogs up, decrease your exposure time.

Turn the light off and develop the image on the screen with a spray of warm water. Spray both sides of the screen until the image area is completely developed. Blot both sides of the screen with newsprint and let it dry in a well lit or sunny area.

Once the screen is dry, put packing tape or masking tape along the inside edges of the screen. Taping it out like this will stop ink from leaking at the side. Also inspect the screen for pinholes. You can block unwanted holes with tape or screen block.

If you have a T-Shirt press, put the screen in the print head and tighten, centering the image on the shirt board.

If you don't, it's not problem. I started running T-Shirts on a kitchen table. Just put a piece of newspaper in side each T-Shirt prior to printing to avoid the ink splooging out to the back of the shirt.

Lay the shirt flat on a table. Put the screen print frame over it. Put a bit of screen printing ink in the end of the frame opposite you. Use one hand to pull the squeegee towards yourself and the other to firmly hold the screen down. Lift the screen to check results. Once the print looks really good, print multiples.

I recommend that beginners use water based screen print ink for ease of use. The leading brands are Speedball and Versatex. Union Aerotex is a top brand of commercial waterbased ink, available from Midwest Sign (the first supplier link above).

Have fun and be patient!

Steve Lafler
Manx Media Custom Screen Printing


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