Industrial production of paper: pulp is produced by mechanically or chemically processing wood or other vegetative materials to extract usable cellulosic fibers as an aqueous slurry. The pulp slurry may be used directly in paper making or it may be shipped elsewhere for processing into paper products. The fundamental industrial operations are divided into two major categories: pulp mill and paper mill. The pulp mill operation includes wood preparation, pulping, deinking, pulp washing, screening and thickening, and bleaching. The paper mill operations include stock preparation, paper machine operation and finishing.