The first chemical treatment for curling hair that was suitable for use on people was invented in the year 1906 by the German hairdresser Karl Nessler (1872-1951). He used a mixture of cow urine and water. The first public demonstration took place on October 8, 1906, but Nessler had been working on the idea since 1896. Previously, wigs had been set with caustic chemicals to form curls, but these recipes were too harsh to use on human skin.