Liquid sorption characterisation of Norway spruce heartwood and sapwood using a multicycle Wilhelmy plate method

Abstract

A multicycle Wilhelmy plate method was applied to study the water and octane sorption behaviour of small Norway spruce veneers. Dry heart- and sapwood samples of varying density were investigated. The results showed a correlation between the porosity and the sorption of octane for all samples, i.e. a higher wood porosity resulted in higher octane sorption. However, no difference in octane sorption was found between heart- and sapwood samples of similar density. The water sorption behaviour was difficult to interpret, probably due to the influence of surface-active wood extractives. It is suggested that the presence of such extractives, particularly in the sapwood samples, increases the sorption of water due to a significant decrease in its apparent surface tension. Hence, the results indicate that the liquid water sorption of spruce heart- and sapwood is strongly influenced by variations in the extractives content rather than by the micromorphology.