Kraft Pulp, Linerboard and Fluting Medium

Kraft ("strong") paper comes from wood chips cooked under pressure at 170–176 °C in white liquor, a solution of sodium hydroxide and sodium sulfide that dissolves the lignin. About half the wood comes out as brown pulp. Softwood pulp makes linerboard and brown kraft paper; hardwood pulp makes the fluting medium. A paper machine forms, presses, dries and reels it. The picture: our diagram of chips, digester and paper machine.