Tear the corner off a newspaper page. Hold it up to the light and
you’ll see them – the fibres that form the building blocks of paper.
Fibres comprise several layers
A tree has countless fibres whose task is to make the tree stable. These fibres are bound together by lignin. A spruce fibre is 3-5 mm long and shaped like a long, hollow spool. The fibre wall comprises several layers, within which clumps of cellulose molecules are organised in fibrils. The fibrils are arranged at different angles, which has a great impact on the strength of the fibre.
Both virgin fibre and recovered fibre
In addition to virgin spruce fibre fresh from the forest, Holmen Paper also uses recovered fibre from collected newspapers, magazines and catalogues. The company’s paper mill in Madrid bases its production entirely on recovered paper. The vast majority of this recovered paper is collected by recovered paper companies that it owns fully or in part. Recovered fibre pulp is also used in the production of several paper grades in Sweden. The proportion varies between 20 and 50 per cent, depending on the grade of paper. In both Sweden and Spain, the collection rate for recovered paper lies above the European average. The picture shows recovered fibre pulp with different kinds of fibre.
Fibre varies with the seasons
Fibre properties may differ between different tree species, but they also differ in trees of the same species. Spruce wood from southern Sweden, for example, is paler than spruce from northern Sweden. The fibres in the same tree can also look different due to seasonal variations. Fibres formed in spring and the warm early summer grow fastest and have thin fibre walls with a more open structure. Growth is at its most intensive then and large quantities of water have to be transported through the open fibre structure. This ‘spring wood’ is followed by ‘summer wood’ when the temperature and growth are lower. The fibres produced now have thicker walls and form a denser structure.