Kraftpaper

Kraftpaper, commonly called kraft paper, is a sturdy paper produced from chemical pulp by the kraft process. It is typically unbleached and brown, but can be manufactured as white kraft through bleaching.

The kraft process uses an alkaline solution of sodium hydroxide and sodium sulfide to break down lignin and separate fibrous cellulose. This yields long, strong fibers and a high pulp yield. The resulting black liquor is recovered for energy and chemical reuse. Bleaching can produce lighter colors or white kraft using oxygen, hydrogen peroxide, or other agents.

Kraft paper is known for high tensile strength, tear resistance, and good fold endurance. It has moderate porosity, good rigidity, and abrasion resistance. It can be produced in a range of basis weights and may be coated or laminated to improve moisture resistance.

It is widely used for packaging, shopping bags, grocery sacks, wrapping paper, envelopes, and as an outer layer in corrugated cardboard. It is also used in bookbinding, crafts, and as liners in food packaging when appropriately treated for moisture resistance.

Variants and sustainability: Brown kraft refers to the unbleached form; white kraft is produced by bleaching. Kraft papers are generally recyclable and often recovered for energy from byproducts; the process is designed to recover and reuse chemicals and heat, reducing waste.