An aluminum potassium or ammonium sulfate, it is supplied in the form of crystals or powder. It has a stong astringent action and it is used after shaving face or body hair in aftershave forumulations and astringent lotions, as well as in powder as a styptic to help stop bleeding from razor cuts and/or nicks. Similar alum based products are also used on animals to prevent bleeding after nail-clipping. Alum in block form (usually potassium alum) is used as an aftershave, rubbed over the wet freshly shaved face. Alum was often utilized as a base in skin whiteners and treatments during the late 16th Century in the Elizabethan fashion. In the 1950s alum was used in rock form to rub on the front short hair of a "crewcut". When the hair dried, it would stay up all day.