Emulsion – Photo emulsion is what makes the modern day screen printing process possible. The emulsion is a substance that reacts to ultraviolet light. Once it has been exposed to the correct ultraviolet wavelength, the emulsion hardens and becomes impermeable. There are many different types of emulsion in the market, as well as many different methods of application. In a later post, I’ll dive into the two most popular methods for coating the screen mesh with emulsion.
Squeegee – A squeegee is a flat, rubber or urethane blade set into a handle. Some people may argue that this is not necessary and that brushes or sponges can be used to push the ink through the screen. They are correct and it can be done, but the results and time consumption can lead to very mixed results. Almost all professional screen printers use squeegees to produce consistent, high quality results.
Scoop Coater – This is a tool that is used to coat the screen with a thin, uniform layer of liquid photo emulsion. Without the scoop coater it is possible to use a squeegee to spread the photo emulsion but this can sometimes lead to uneven thickness and poor exposure results.
Film Positive (Artwork) – The film positive refers to the artwork which is typically printed or drawn onto on a transparent medium. The artwork must be opaque in order to produce proper results when exposing the screen. One of the cheapest ways to create the film positive is to print directly onto transparency film from your laser or ink jet printer. Be sure to have the printer settings set to produce the darkest black possible for your artwork. As an alternative, vellum can also be used as a film positive. If you are using vellum add approximately 20% to the exposure time due to the reduced transparency of the vellum.
Light Source – In order to properly expose the emulsion and “burn” the screen, a light source is required that contains Ultraviolet Radiation in the 350-420 Nanometer spectrum. Fluorescent unfiltered tubes, metal halide lamps and even the sun can be used to expose a screen.
Hinge Clamps – These are essential if you plan on screen printing paper goods or other flat objects. The hinge clamps you to keep your screen in the same positiong, allowing for easy registration and consistent prints.
Tape – There are kinds of tape that I use on a regular basis. The first is painter’s tape which use for easy registration of screens, psoitioning acetate, etc. The second type of tape that I use is a tape made for screen printing which is water and solvent resistent. This one is used for taping my screens. I have also used plastic packing tape with great results.
Yellow Light Safe Bulb – During the coating and exposure process it is important to create light safe conditions. Premature exposure to UV light (sunlight, regular household lights, etc) can pre-expose the coated screens resulting in poor results. Yellow bulbs filter out the specturm of light that can expose the emulsion, making it “safe” to work under those conditions.
