VARIATIONS IN HOT-WATER EXTRACTIVES CONTENT AND DENSITY OF COMMERCIAL WOOD VENEERS FROM BLACKBUTT (EUCALYPTUS-PILULARIS)

Extractives content and wood densities of commercial veneers of blackbutt (Eucalyptus pilularis) were determined. The extractives contents varied from 3.3% to 14.3% on the basis of oven dry weight of unextracted wood, whilst the wood densities varied from 727 kg/m(3) to 995 kg/m(3) Colour analysis of these commercial veneers was carried out and the colours of the veneers were described using the CIE L*a*b* scale. Compared with the data from the colour analysis, the extractives content of the commercial veneers was well correlated to redness (a*) values and a regression equation has been obtained. Further studies using the colorimetric and the extraction methods revealed that this colorimetric method can be an effective way to estimate the amounts of extratives on the surface of blackbutt veneers. Some of the commercial veneers had dark coloured areas, particularly on the loose side (the side of the veneer containing peeler checks). This colouration was found to be due to deposits of ellagitannins in amounts of up to 22.9% of the dry weight of the unextracted shavings which had apparently been carried by free water from within the veneer to the surface in the course of the veneer drying process.