Cuprammonium rayon

The solution is passed through a spinneret and the cellulose is regenerated in hardening baths that remove the copper and ammonia and neutralize the caustic soda.

Cuprammonium rayon is usually made in fine filaments that are used in suit jacket linings as well as lightweight summer dresses and blouses, sometimes in combination with cotton to make textured fabrics with slubbed, uneven surfaces.

[4] Swiss chemist Matthias Eduard Schweizer (1818–1860) discovered that cellulose dissolves in tetraaminecopper dihydroxide.

Max Fremery and Johann Urban developed a method to produce carbon fibers for use in light bulbs in 1897 (the factory closed in 1902).

[5] Production of cuprammonium rayon for textiles started in 1899 in the Vereinigte Glanzstoff Fabriken AG in Oberbruch near Aachen.

Brown cupra (also known as cupro or Bemberg) fabric made of rayon
Lab demonstration of the process. When a solution of cellulose in cuprammonium hydroxide comes into contact with sulfuric acid, the cellulose begins to precipitate from the solution. The sulfuric acid reacts with a complex compound of copper and dissolves it. Thin blue fibers of rayon are formed. After some time, sulfuric acid reacts with the complex compound and washes out the copper salts from the fibers. The fibers become colorless.