A permanent wave, commonly called a perm or permanent (sometimes called a "curly perm" to distinguish it from a "straight perm"), is a hairstyle consisting of waves or curls set into the hair. The curls may last a number of months, hence the name. Perms may be applied using thermal or chemical means. In the latter method, chemicals are applied to the hair, which is then wrapped around forms to produce waves and curls. The same process is used for chemical straightening or relaxing, with the hair being flattened instead of curled during the chemical reaction. History The first person to produce a practical thermal method was Marcel Grateau in 1872. He devised a pair of specially manufactured tongs, in which one of the arms had a circular cross-section and the other a concave one, so that one fitted inside the other when the tongs were closed. The tongs were generally heated over a gas or alcohol flame and the correct temperature was achieved by testing the tongs on a newspaper; if the paper browned slightly it was about right. The waving itself was safe if care was taken to keep the tongs away from the scalp. The procedure was to comb a lock of hair towards the operator, moving the comb slowly with one hand to maintain some tension, while applying the tongs to the hair successively down the lock of hair towards the point. Each time the tongs were applied, they were moved slightly in a direction normal to the lock of hair, thus producing a continuous flat or two-dimensional wave. Skill using the wrist could produce slight variations of the wave. Thus, Marcel waving produced a two-dimensional wave, by thermal means only and the change was produced by plastic flow of the hair, rather than by any chemical means. Because of the high temperature used, the process tended to degrade the hair. However, in spite of its drawbacks, forms of Marcel waving have persisted until today, when speedy results and low cost are important. Up until the 1920s long hair was standard for women. The flappers of the 1920s cut their hair short (the "bob") as a form of rebellion against tradition. As the demand for self-determination grew among women, hair was shortened so that it did not pass the lower end of the neck. This was not only a political gesture but a practical one, as