In 1884, Hilaire de Chardonnet started the first artificial fiber factory based on regenerated cellulose, or viscose rayon, as a substitute for silk, but it was very flammable. In 1907 Leo Baekeland invented the first synthetic polymer, a thermosetting phenol-formaldehyde resin called Bakelite. Around the same time, Hermann Leuchs reported the synthesis of N-carboxyanhydrides and their high molecular weight products upon reaction with nucleophiles. But Leuchs did not call them polymers, possibly due to the strong views held by Emil Fischer, his direct supervisor, denying the possibility of any covalent molecule exceeding 6,000 daltons. Cellophane was invented in 1908 by Jocques Brandenberger who squirted sheets of viscose rayon into an acid bath.