Screen printing is a printing technique that uses a printing plate (made with a wooden or aluminium frame) with a fine nylon mesh stretched over it. The mesh is coated with a light sensitive emulsion, which when dry will block the holes in the mesh.
The image that needs to be printed is output to film either by camera or image-setter and is sandwiched together with the mesh, it is then exposed to ultra-violet light in a device called a print-down frame. After curing the screen is washed with a jet of water to wash away the light sensitive emulsion that has not been hardened by the ultra-violet light. This leaves you with an open stencil which corresponds exactly to the image that was supplied on film.
The screen is fitted on a press and hinged so it can be raised and lowered. The substrate to be printed is placed in position under the screen and ink is placed on the top side of the screen, (the frame acts also as wall to contain the ink ). A rubber blade called a squeegee (similar to a giant wind-screen wiper) is pulled across the top of the screen; it pushes the ink through the mesh onto the surface of the substrate you are printing, with a return stroke the mesh is flooded with the squeegee before printing the next impression.
This printing technique is also known as silkscreen, serigraphy, and serigraph printing. One colour is printed at a time, so several screens can be used to produce a multicoloured image or design.