In the water-swollen state, water is the major component of the cell wall of a pulp fibre-its amount often exceeding that of the sum of the other components. How this amount of water is accommodated in the cell wall obviously has a great bearing on the structure of the solid phase and the properties of the wet fibre as a whole.
It is proposed that in the wall of the wood fibre, water is held in a micro-porous gel of hemicelluloses and lignin which is distributed as fine platelets within a cellulose skeleton consisting of much distorted lamellae. As the lignin and hemicelluloses are removed by pulping, the amount of water in the wall increases as water fully occupies the spaces previously shared with these components. The subsequent mechanical action of beating is visualised as causing the slit-like spaces occupied by water to progressively link up and the coarser lamella separations to enter the range of visibility by optical microscopy. The entry of additional water into the cell wall, as induced by pulping or mechanical action, is believed by its delaminating action to bring about plasticisation of the wood fibre, a necessary prerequisite to papermaking.