paperimassa

Paperimassa, or paper pulp, is a thick slurry of cellulose fibers suspended in water and used as the primary raw material for making paper and paperboard. The composition depends on the pulping method and added substances such as fillers, pigments, and sizing agents, which influence brightness, opacity, printability, and resistance to water.

Pulp can be produced from wood and non-wood fibers or from recycled paper. Mechanical pulps are created by mechanically separating fibers, typically by grinding or refining, which yields high fiber content but retains much of the lignin and results in lower brightness. Chemical pulps are produced by cooking wood chips with chemicals (such as kraft or sulfite processes) to dissolve lignin and free cellulose fibers, producing stronger, brighter paper. Recycled pulp is obtained by repulping collected paper and removing inks and contaminants through deinking and washing. Bleaching may be used to increase brightness, with modern practices often aiming for chlorine-free processes.

The properties of paperimassa depend on fiber length, bonding potential, and the presence of fines and fillers. Longer fibers and well-developed bonding increase strength, while fines and bleaching influence brightness and smoothness. Pulp is refined and sometimes blended to achieve target sheet properties before forming into a continuous sheet, removing water, pressing, and drying.

Environmental considerations include energy and chemical use, effluent treatment, and the role of recycling. Recovered fibers reduce virgin-fiber demand, and advances in deinking and bleaching aim to lower environmental impact. Pulp quality is a key determinant of paper performance across printing, packaging, and tissue grades.