The present invention comprises the following successive stages: (i) treating the hair by topical application of a hair treatment composition comprising 2 to 25 wt% of one or more C2-4 monoaldehydes; (ii) mechanically treating the treated hair A method of shaping hair comprising the step of shaping is provided.本発明は、次の連続段階:(i)2から25wt%の1以上のC2-4モノアルデヒドを含む毛髪処理組成物の局所適用によって毛髪を処理し;(ii)処理した毛髪を機械的に成形する段階を含む、毛髪を成形する方法を提供する。