What is a stencil?

A stencil is a template used to draw or paint identical letters, symbols, shapes or patterns every time it is used. Stencil technique in visual art is also referred to as pochoir. Stencils are formed by removing sections from template material in the form of text or an image. This creates what is essentially a physical negative. The template can then be used to create impressions of the stenciled image, by applying pigment on the surface of the template and through the removed sections, leaving a reproduction of the stencil on the underlying surface. Aerosol or painting stencils must remain contiguous after the image is removed, in order for the template to remain functional. Sections of the remaining template which are isolated inside removed parts of the image are called islands. All islands must be connected to other parts of the template with bridges, or additional sections of narrow template material which are not removed.

A related technique (which has found applicability in some surrealist compositions) is aerography, in which spray-painting is done around a three-dimensional object. This technique is comparable to the paintings in caves dating over +10,000BC, where hands were used to create hand print outlines amongst other artwork, such as paintings of animals. The artist would spray pigment around his hand with his mouth. A hollow bone or reed may have also been employed to direct the stream of pigment.

Silk-screen printing also uses a stencil process, as does mimeography. The masters from which mimeographed pages are printed are often called "stencils." Stencils can be made with one or many colour layers using different techniques, with most stencils designed to be applied as solid colours.

During silk-screening and mimeography the images for stenciling are broken down into color layers. Multiple layers of stencils are used on the same surface to produce multi-colored images.