Method for decolouring keratinous material dyed with an organosilicon compound and a pigment

A method for decolouring keratinous material, which has been dyed by the application of at least one organosilicon compound and at least one pigment, by applying a decolouring agent comprising at least one aluminium salt to the coloured keratinous material. Preferably, the decolouring agent is applied to keratinous material which has been dyed by application of at least one C1-C6 alkoxysilane, and at least one pigment. Preferably, the decolouring agent contains at least one aluminium salt selected from: aluminium chlorohydrate, aluminium zirconium tetrachlorine hydrate, aluminium sesquichlorohydrate, and aluminium chloride. The at least one aluminium salt may be present from 9.0 to 28% by weight of the decolouring agent, and may be applied to the dyed keratinous material and rinsed off again after an application time, preferably 3 to 30 minutes.