Enzymatic treatments for improved dyeing of solid wood

Full penetration-dyed solid wood has the advantage that furniture or other items fabricated from it do not require additional painting or staining. However, anatomical barriers along potential dye infiltration pathways may result in unsatisfactory dyeing in terms of depth of dye penetration or colour intensity and uniformity. Dyed wood items, even those intended for interior use, should also possess a certain degree of water fastness. In the present paper, full-thickness dyeing of radiata pine blocks was achieved with fibre-reactive and direct dyes as well as pine tannin. Leaching of the treated blocks in cold water removed excess dye but the target colours were well retained. Pectinase pre-treatment of wood blocks was shown to increase the uptake of fibre-reactive and direct dyes by tracheid cell walls and the uptake of tannin by rays, resin canals, and tracheid lumina. In the case of a direct dye and pine tannin, pectinase treatment markedly increased the intensity of the target colours. Combining tannin with laccase to achieve covalent bonding of tannin to wood lignin was associated with a small, albeit not statistically significant, shift towards the target colour.