20"x24"UV Exposure Unit UV Exposure Unit is an important tool in screen making. Working principle: screen printing screens are coated with a light sensitive emulsion using a scoop coater. When the emulsion is dry, place a positive print of your image on the screen. Once you burn the screen, the emulsion that did not get any UV will wash out of the screen exposing the tiny pin holes. The surrounding areas that were exposed to UV will be cured. Hence the ink will pass through screen onto your substrate.