Screen Printing Equipment
Screen printing, also called serigraph, was invented 2000 years ago in the Far East. Originally the screen printer's screen was made of silk and a paper stencil was stitched onto it to control the printed area.
Cut to the early 1900s. Screen printing is re-vamped and has since become a common method for printing on textiles. Screen printing is most often seen on t-shirts and the screens are usually made of a mono filament mesh along with emulsion to make the stencil. The screen is coated with emulsion and allowed to dry and harden. The emulsion used is very light sensitive so the stencil is made by coating the screen and then exposing it to light. If you do not expose it to light, the emulsion will remain water soluble and can be washed out but once you expose it to light water will not dissolve it. Once the stencil is designed and put on the screen, you are ready to apply it to your t-shirt or other textile.
Equipment
The most common type of screen printing equipment is the manual rotary machine. These machines have two wheels that spin independent of each other. The upper wheel has the screens clamped to arms on spring loaded hinges to hold it up in the air when not being used. You place your material on the machine and it will press the stencil onto it and paint around it.
The flash unit is a box that uses infrared heat to cure the wet ink. It cures it just enough so that the ink is not wet. The reason for the flash unit is to make the ink film thicker. An impression is made and then flash dried and allowed to cool. Then a second impression is made. Double impressions reinforce the design and also allow for a second color to be screen printed.
The drier sits on the end of this conveyor belt operation. The t-shirt is carried on the conveyor belt underneath the heating element and allowed to dry there. The ink and t-shirt are heated to 320 degrees in order for the ink to bond with the fabric. Then it gets dropped into a hopper and you are ready to go again.
An emulsion cup is used to coat the silk screen with emulsion. It is like a trough that holds the liquid emulsion and allows it to be spread evenly across the screen. The emulsion can also be removed from the screen so that the screens can be reused, otherwise screens add up and become very expensive. The process is called reclaiming. First the ink is scraped out of the screen and ink wash is used to clean it. Then the screen is sprayed with emulsion remover and a high pressure sprayer. After the emulsion has been removed the screen is degreased and scrubbed on both sides and is ready for reuse. The screens must always be clean and dry before recoated with emulsion.
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