Currently Daum is the only commercial crystal manufacturer employing the pâte de verre process for art glass and crystal sculptures, a technique in which crushed glass is packed into a refractory mould and then fused in a kiln. The Daum brothers quickly moved on to become one of the major forces in the Art Nouveau movement, seriously rivalling Gallé, so much so that when Émile Gallé died in 1904 they became the leaders in the field of decorative glass. In 1906 Daum revived pâte de verre , an ancient Egyptian method of glass casting, developing the method so that by the 1930s Daum's window panels used pâte de verre for richness instead of leaded or painted glass.