PARTIAL SHRINKAGE AND PROPORTION OF CRACKS IN JUVENILE AND ADULT WOOD OF Eucalyptus grandis W. Hill ex Maiden

Resumo

Drying defects which modify the structure and dimensions of wood are extremely harmful, causing limitations of use. It is known that the anatomical structure of wood has direct influence on the drying quality, in which weaker tissues lead to higher incidence of defects. As the wood drying process advances, it leads to the removal of bound water and, consequently, to the shrinkage of cell walls, which makes wood shorten its dimensions, causing defects related to this phenomenon, such as end and surface checks. The aim of this work was to evaluate the difference in partial shrinkage and proportion of cracks in Eucalyptus grandis juvenile (with pith) and adult wood (without pith) during natural air drying. The proportion of cracks was measured according to Brazilian Standard NBR 9487: Grading of hardwood lumber, and the partial shrinkage was obtained by direct measurement method. There was not a statistically significant difference of partial shrinkage between juvenile and adult wood. Lumber from juvenile wood presented worse quality in natural air drying than adult wood. The influence of wood position (juvenile or adult) in log exerted higher influence on drying quality than shrinkage.