A blow dryer or hair dryer is an electromechanical device designed to blow cool or hot air over wet or damp hair, in order to accelerate the evaporation of water particles and dry the hair. Blow dryers allow to better control the shape and style of hair, by accelerating and controlling the formation of temporary hydrogen bonds inside each strand.
These hydrogen bonds are very powerful (allowing for stronger hair shaping than even the sulfur bonds formed by permanent waving products), but are temporary and extremely vulnerable to humidity. They disappear with a single washing of the hair.
Hairstyles using blow dryers usually have volume and discipline, which can be further improved by the use of styling products and hairbrushes during drying to add tension, hold and lift.
Blow dryers were invented around the end of the 19th century. The first model was created by Alexander F. “Beau” Godefroy in his salon in France in 1890. The handheld, household hair-dryer first appeared in 1920. Blow dryers are used both in the beauty salon by professional stylists, and in the average household by consumers.
Most models use coils of wire that have a high electric resistivity and heat rapidly with an electric current. A fan usually blows ambient air past the hot coils resulting in heated air effective for drying. The heating element in most hairdryers is a bare, coiled nichrome wire that is wrapped around insulating mica heating boards. Nichrome wire is used in heating elements, because of two important properties: it is a poor conductor of electricity and it does not oxidize when heated.