The photo emulsion method is common for printing highly detailed images and text. It utilizes a screen made of fine mesh stretched tightly over an aluminum or wooden frame. The screen is coated with a ultra-thin layer of photosensitive emulsion and allowed to dry.
Once dry, an opaque version of an image is laid on the screen, and the bottom of the screen is exposed to light. When the emulsion is exposed to light, it solidifies and binds to the fabric. The areas blocked by the opaque image are not exposed to light and remain water soluble. After the exposure process is completed, the screen is sprayed with water to remove excess emulsion from the non-exposed image areas. These areas are now porous and allow ink to transfer through during the printing stage. Finally, the screen is placed onto the medium to be printed (fabric, paper, etc.), and the ink is pressed through the screen.
The stencil method is less complicated and is easily done at home. A piece of water-resistant paper (such as contact paper) is cut to match the size of the screen. The image is hand-drawn or traced onto the paper. The image is then cut out, the paper outline is laid on the screen, and the printing process is completed the same way as in photo emulsion.
The drawing fluid method is also less complicated than photo emulsion. A drawing fluid is brushed onto the screen in the areas that are to be printed and allowed to dry. Once the fluid is dry, a screen filler is spread over the entire underside of the screen. In areas where drawing fluid has been applied, the filler remains water soluble. When the filler is dry, the screen is sprayed with cold water to remove the drawing fluid. After the screen is dry, it is ready to be used to print, with a water-based ink, in the normal screen printing process.
With all types of screen printing that use an emulsion or filler, it is important to reclaim the screen. Reclaiming the screen begins by removing all ink. The emulsion, or filler, is then removed by spraying the screen with a mixture of water and emulsion remover chemicals, which are mostly made up of sodium metaperiodate. Then, the screen is immediately rinsed with clean water.