The present invention is directed towards a cosmetic assembly, of use for the treatment of keratin fibres, comprising a fluid cosmetic composition containing at least particles in the dispersed state in a liquid medium, said composition being solidifiable via the aggregation of said particles； and a device (1) comprising a mould (2), the mould (2) comprising at least one cavity (5), into which or each of which at least one of said fibres can be at least partially introduced, for the purposes of moulding said composition onto at least one part of said fibre(s) present in the cavity or cavities (5). The present invention is also directed towards a process for cosmetic treatment of one or more keratin fibres.
