
 Possibilities for compositional tailoring of Norway spruce (Picea abies
 L. Karst.) wood using a hydrophobic oil impregnation process

ZusammenfassungImpregnation with hydrophobic oils offers non-toxic options for preserving Norway spruce (Picea abies L. Karst) wood that could potentially be used to tailor the properties
 of wood products, especially those used in exposed conditions. The objective of this study was to quantify
 the effects of the water-filled porosity and density of Norway spruce wood and treatments (applied to set
 the wood’s water contents at desired test levels) prior to impregnation with the linseed oil derivative
 Linogard by the Linotech process on its oil retention. Retention of oil differed significantly between
 tissue types. Dried specimens always retained less oil than corresponding undried or rewetted specimens.
 Furthermore, water-filled porosity and density had significant effects on oil retention levels within tissue
 types, allowing linear regression equations to be developed that gave good predictions of oil retention
 parameters for different tissues, with R2 values ranging from 0.66 for mature
 heartwood to 0.85 for mature sapwood. Thus there is scope to use hydrophobic oil impregnation processes
 for producing compositionally tailored wood materials with specified properties.

Moisture sorption and swelling of Norway spruce [Picea abies (L.) Karst.] impregnated with linseed oil
Abstract The moisture sorption and swelling of spruce specimens impregnated with linseed oil and unimpregnated controls were studied in two sorption experiments: from 0 to 55% relative humidity (RH) and from 55% RH to water saturation. Sorption isotherms were also determined using a sorption balance. The impregnated specimens had lower rates of both moisture sorption and swelling than the unimpregnated controls; however, there was no significant difference in final moisture contents. In addition, the linseed oil impregnation did not improve the dimensional stability of the wood; in most cases the specimens impregnated with linseed oil swelled more than the unimpregnated controls. For the impregnated specimens, reductions in swelling rates were in most cases seen without corresponding reductions in final swelling. The moisture sorption rate was reduced for the impregnated specimens but there were generally no reductions in equilibrium moisture content.
A reexamination of some deviations from Darcy's Law in coniferous wood
SummaryA number of workers have noted a marked decrease of wood permeability with increasing specimen length, and to date a model proposed by Bramhall has been used to explain the phenomenon. This describes the effect of random blockages on the permeability of an anisotropic porous medium. However, the model does not allow for the fact that transverse flow may allow longitudinal flow paths to circumvent blockages to some extent, so some deviation from it can be expected. The issue is an important one if laboratory experiments are to be used as a basis for the prediction of the behaviour of wood during impregnation or drying on a commercial scale. A modified model which allows for transverse flow is therefore developed. New experimental evidence which cannot be explained by the Bramhall model, but which can be explained by the new model, is presented.