Paper making. Historical artwork of rotary boilers in a paper mill. Cloth rags and paper are loaded into the boiler's drum and boiled with caustic soda to clean them and breakdown their fibres. This process takes several hours. The resulting pulp will be beaten to reduce its water content and then put through rollers to form paper. Engraving taken from insGrands Hommes et Grands Faits de l'Industrieins (1880).