Many people who visit this site are beginners and are now getting into the wonderful world of screen-printing. So I have created this down and dirty quick primer leading into exposing, screen printing, screens. I would though recommend picking up a copy of How to Print T-Shirts for Fun and Profit! By: Scott Fresener this is a huge book and will be a valuable reference for your shop.
Ok, let’s get to it...
Screen-printing screens are coated with a light sensitive emulsion using a scoop coater. (I personally employ Ulano QTX emulsion) Once the screen is coated and dried, every the little holes in the screen are covered and ink will not pass through the screen mesh. Some ultraviolet light that the screen is exposed to, will harden the emulsion. People use all sorts of methods to expose screens to ultraviolet light including: The sun, un-filtered black lights, quartz, mercury vapor and metal halide lamps. Of course a few sources work better than others, and like computers… faster usually means more cash.
Once the screen is dry, you place a positive print of your image on the screen. This image needs to be dark enough to block light as of passing through, remember and light that gets to the emulsion will create it hard and will not wash out. Once you burn the screen, the emulsion that did not get some UV will wash out of the screen exposing the tiny pin holes. The surrounding areas that was exposed to UV will be cured. Hence (sophisticated word practice on..) the ink will pass through and onto your substrate (T-shirt,etc..)
I started with a 500 watt quartz $8 dollar no holler work light. It works ok and is a good place to start. Then I graduated to the exposure unit below. With that being said. Here are a few pictures of my home built screen printing exposure unit. This unit uses 6 F20T12BL lamps. I had to special order them from a local lighting company. The cost for each lamp was about $9.00. The black light lamps are installed 2″ away from 24″x24″ 1/4″ plate glass. I also installed 2 lamp sockets for screw in type fluorescent lamps. These are used for tracing and lining up art. The switch on the side controls these lamps. In the receptical I plug in a Timex countdown timer and plug black lights into that. Using Ulano QTX emulsion and clear overhead film, I get a good exposure in 15 seconds. This unit works very well.
So there you have it… The total was about $100 bucks give or get. You will have fun building this exposure unit, so get to it… And again, check out How to Print T-Shirts for Fun and Profit! By: Scott Fresener