If you’re thinking you can take a screen off your window at home, add some emulsion to it, and start printing shirts, this article is for you. I’d like to gently talk you down from that idea. You can do better. Preparing screens is a critical part of making good prints. This is how the pros do it:
We’re not really in the business of making new screens. We’d rather be making awesome shirts for you! If we did make screens, this is what we would do:
Screens are constructed by stretching a polyester fabric over a wood or aluminum frame. As you can imagine, the fabric is pretty tight, to withstand the stress of repeatedly having ink pushed through it with a squeegee. The thread count of the screen plays a large role in print quality, and is a subject for another blog post. The fabric is glued in place, ready for printing.
Making a bare screen print ready involves a simple and ingenious technique.
The various layers of a design are printed onto a transparent film positive, which is then placed over a screen with ultraviolet sensitive photo emulsion. The emulsion hardens, or finishes, with exposure to ultraviolet light. Exposure takes place inside a machine that resembles a large copier. The undeveloped screen is laid on it with the transparency in between screen and light source. A sealed layer of plastic or fabric is pressed against the other side of the screen so that no additional, unwanted light enters the process.
Amateur screen printers sometimes finish their screens with natural sunlight, which is a legitimate source of ultraviolet light. However, it lacks the uniform control of ultraviolet light bulbs. For instance, clouds can pass before the sun during finishing. An ultraviolet bulb is also a more intense source of UV radiation, like a tanning bed for screens.
Where the emulsion is shielded from the light by the dark areas of the transparency, it is unfinished, and is easily washed away with a high-pressure stream of water. To ensure that all the little bits of emulsion wash away, a pressure washer should be used to make sure the fine details of your design are washed out.
When ink is pressed through the screen, or the screen is “flooded”, it passes through the screen where there is no emulsion, and the negative areas of the screen become the positive areas of the print.
In a perfect world, a print shop would hang on to the screens they use to make amazing designs. When you want another print of your favorite design, the screens would be waiting in the library. Just make the call.
We don’t live in a perfect world. As soon as your order is finished, the screen is sent back to the reclaim room, where it is shuffled back into the system. It only holds your design long enough to finish your order. This way, print shops keep a reasonable number of screens on hand at any one time, and keep costs down.
The first step in reclaiming a screen is to remove any ink left on the screen and then remove the finished emulsion. The product that removes emulsion is cleverly named emulsion remover, and does just that. But that’s not the last step.
Screens get dirty. A screen that has sat around for a while probably needs a little cleaning. Even new screens have a small amount of unwanted particulates on them. Before a screen is coated, it must be washed.
Using a scrub brush, water, and some degreaser, the screen must be methodically scrubbed to remove any debris. After the screen is fully scrubbed and rinsed, it is left to dry completely, before the cycle begins anew.