Skip to content
glossary/kraft-pulp

Kraft pulp

Also: kraft pulp, sulfate pulp

Chemical pulp produced by cooking wood chips with sodium hydroxide and sodium sulfide. The dominant pulp process globally.

Kraft pulping cooks wood chips in a digester at about 170 °C with a mixture of NaOH and Na2S (the 'white liquor'). The cook dissolves lignin and separates cellulose fibers with minimal damage, producing a strong, dark pulp. Kraft pulp represents about 80% of global chemical pulp production.

Unbleached kraft is brown and used in sack paper, containerboard, and wrapping. Bleached kraft (BKP) is white and used in printing, tissue, and premium packaging. Softwood kraft gives long fibers for strength; hardwood kraft gives short fibers for smoothness and opacity.

Related
  • Bleaching. Chemical removal of residual lignin from chemical pulp to produce white pulp. ECF (chlorine dioxide) and TCF (oxygen, ozone, peroxide) are the two major systems.
  • Softwood pulp. Pulp from coniferous trees (pine, spruce, fir) with long fibers (2 to 4 mm) that provide strength and tear resistance.