Screen printing form is a somewhat fancy name for a screen that’s ready for printing, ie. it consists of a frame, a mesh which is the carrier of screen printing stencil, and the screen printing stencil itself. That last term is sometimes used as a synonym for the printing form, but according to most literature, it should apply only to the layer deposited on mesh in order to block it (in practice that’s usually a layer of exposed photosensitive emulsion).
Din 1661 norm, which is a screen printing industry standard, defines basic characteristics of screen printing form as follows:
ZS – mesh; R – frame; RA – external dimensions of the frame; RJ – internal dimensions of the frame; WR-Q – ink rest; ASO – stencil area; AQ – squeegeeing area; A1 – printed image area; ASTO – open mesh
Screen printing forms can be divided into: flat, non-flat and cylindrical (used in rotary screen printing). Flat forms are used for printing on flat surfaces as well as on surfaces that are non-flat, but rotate in the printing process (eg bottles). Non-flat forms are used for printing on objects of different shapes and sizes and their shape mathes the shape of the object being printed on. Forms used in rotary screen printing (eg on fabrics or wallpapers) are thimble (sleeve) shaped and usually made of metallised polyester, nickel or steel. Sqeegee is placed inside the form, to which through special pipes ink is supplied. In the printing process ink is forced through the mesh outside the sleeve and onto the fabric, as shown in the diagram below.