Abstract: The permanent shaping agent containing one or more hair keratin-reducing active substances is adjusted by means of stiffening additives to a consistency that is viscous to cream-like at room temperature with a viscosity of over 100 mPa.times.s.The stiffening additives are selected such that the permanent shaping agent, upon warming to a temperature with a temperature range between 25.degree. and 42.degree. C., undergoes a decided loss of viscosity of over 60% with respect to the initial viscosity, to a value under 50 mPa.times.s, i.e., becomes fluid within this temperature range.The permanent shaping agent of raised viscous or creamy consistency is applied to curled hair on curlers and then the viscosity of the permanent shaping agent is lowered, by elevating its temperature in situ, so that the liquified agent penetrates into the hair on the curlers.