Relationship Between the Anatomical Structure and the Swelling of Conditioned Wood Surfaces

Abstract

The influence of swelling on the roughness of rehydrated, machinery-treated wood surfaces of Millettia laurentii De Wild. (Wengé) was studied under controlled climate conditions. The surface roughness of transverse, radial, and tangential planes was quantified by high resolution laserscan measurements with an accuracy of ±2 μm and an optical resolution of 8 × 50 μm. The surface profiles were compared with the anatomical structure of the xylem in the surface layer of the samples. The surface roughness of swollen samples increased significantly compared to unswollen samples. Higher surface roughness was found on swollen radial and tangential planes compared to swollen transverse planes. The high increase in roughness of conditioned radial and tangential planes was due to the higher swelling of tissue zones dominated by fibres compared to zones dominated by axial parenchyma, ray parenchyma, and vessels. In thinner rehydrated samples the surface roughness was lower than in thicker samples. Although the increase of surface roughness of the rehydrated samples was only in the range of 10 to 60 μm in these experiments, the gloss level of rehydrated coated surfaces decreased significantly. The results are discussed with special regard to high quality surface finishing of wooden furniture.