• Longest fiber in the range. At 2.5 to 4.5 mm, softwood kraft fibers bridge across many neighbors and transfer load through the network rather than through the wall thickness alone.
• Highest tear and burst resistance. The same fiber length that carries compression also resists the propagation of a tear once one starts, which matters for parts handled repeatedly.
• No bleaching chemistry. The brown color is residual lignin left in place. Skipping the bleaching stage removes a chemical process step and the effluent that goes with it.
• Compostable without qualification. Uncoated kraft is cellulose and lignin, both of which break down in a composting environment. Nothing in the material works against EN 13432 or ASTM D6400 chemistry requirements.
• Takes embossing cleanly. Long fiber holds a formed edge, so embossed detail stays sharper than it does in short-fiber furnishes.
• Blends well as a strength carrier. Most production furnishes use kraft as a proportion rather than at 100%, adding structure to a short-fiber base that handles detail and finish.

The kraft process itself is why this fiber performs. Wood chips are cooked in sodium hydroxide and sodium sulfide, which dissolves lignin and separates fibers while leaving the cellulose chains largely intact. Mechanical pulping, by contrast, grinds the wood and shortens fibers in the process. The kraft route costs more and yields less pulp per tonne of wood, and it produces a fiber that nothing else matches on strength.

The trade is appearance and cost. Kraft is brown, and it will not reach a white or pale finish without bleaching, which is a different material. It also sits at the top of our price range because virgin fiber competes against every other use for the same wood.