Polishing gives the crystal its brilliance and erases any traces of tools or moulds. The repolished satin finish, dear to Lalique, requires manual polishing in order to achieve the desired gradation. There are two methods of polishing: chemical and mechanical. Chemical polishing consists of soaking the piece partially or completely in a hydrofluoric acid bath. This gives the crystal a clear and shiny appearance. In the mechanical polishing process, the work piece is brought into contact with a polishing wheel which gives it a shiny appearance (photo). Polishing is the last operation before signing.