A gasket is a form of a static seal that fills the space between two or more mating surfaces. Gaskets are generally used to prevent leakage from or into the joined objects while under pressure. Gaskets are also used to fill irregularities on the mating surfaces.
Gaskets are commonly produced from sheet materials. One of the most common sheet materials used early on was asbestos but due to health concerns with asbestos exposure non-asbestos is used. Gaskets are usually made from a material that is to some degree yielding and able to deform and tightly fill the space between surfaces.
Some gaskets also require sealant to function properly. Gaskets are normally made from a flat material such as paper, rubber, silicone, metal, cork, felt, neoprene, nitrile rubber, FPM, graphite, fiberglass, PTFE, polyurethane or other plastic polymer.
One of the commonly known gaskets are pipe flange gaskets. These can be with or without bolt holes. The gaskets without bolt holes are commonly called "ring gaskets" and the ones with bolt holes are known as "full face gaskets". These are usually cut one of two ways. Die cut which is the simple method of taking a sheet of material and having the gasket shape "punched out" of it. The latest technology of doing this type of gasket is by "water-jet" where a thin stream of water is pressurized and cuts the shape of the gasket.
Another type of gasket is a spiral-wound gasket. This type of gasket is comprised of a mix of metallic and filler materials. Generally the gasket has a metal wound outwards in a circular spiral with the filler material usually of a flexible graphite wound in the same manner but starting from the opposing side. This results in alternating layers of filler and metal. The filler material acts as the sealing element with the metal providing structural support.
Other types of gaskets are quick disconnect or hose fitting gaskets and envelope gaskets. There are many shapes and sizes of gaskets made of many materials.