Kraft paper

Kraft paper is the paper with the highest strength for the production of eg paper bags, abrading sheets, slip sheets. It consists of almost 100% of cellulose fibers, only starch, alum, and glue can be added to provide surface effects, and increases in strength.

The raw materials are particularly suitable long-fibered softwood (eg spruce, pine) and especially slowly grown wood from Nordic countries. In addition, straw is used. The use of wastepaper containing many damaged fibers would reduce the strength. Also fillers in graphic papers account for a major chunk of the mass, for example, can not be used.

The extraction of the pulp from the wood by the sulfate process produces the highest strength.

A further improvement is provided by the grinding of the pulp. This so-called splice fibrils on the fiber surface that stick to each other and thus provide for networking. The achievable strength increases at the beginning of grinding too much, but then levels off.