MANUAL ON THE PROPERTIES AND USES OF LESSER ... - ITTO

5. TECHNOLOGICAL PROPERTIESRelative DensityVolumetric shrinkageStrength PropertiesRefers to the oven-dry mass weight of woodto the mass weight of an equal volume ofwater measured at a certain temperature. Itis an important parameter in determining agood approximation of the latent strength ofa particular species in the absence of actualstrength test results. It is also useful inestimating charcoal and pulp yields, gluing,nail holding and shrinkage characteristics ofa given wood species. For practical purposes,tree species are classified into 5 relativedensity c1assess namely: Class I - High RD(0.701.and above), Class 11 - Moderately highRD (0.601-0.700), Class III - Medium RD(0.501-0.600), Class IV - Moderately low RD(0.401-0.500), and Class V - Low RD (0.400and below)Refers to the reduction in total dimension ofwood after removal of bound water belowfiber saturation point. In the longitudinal "direction, Le. along the grain, shrinkage isusually insignificant. Shrinkage on thetangential direction (parellel to growth rings)for most species is about twice as great as inthe radial directions (right angles to growthrings). Grouping to shrinkage values aids theuser proper use and avoidance of defects. Treespecies are classified into 5 volumetricshrinkage (VS) values: Class I - Low VS(7.8% and below); Class 11 - Moderately lowVS (7.9% to 10.5%); Class III - Medium VS(10.6% to 13.2%); Class IV - Moderately highVS (13.3% to 16%); and Class V (16.1 % andabove)Refers to the qualities of wood thatindicateits ability to resist applied external forces.They are important criteria in determining therelative suitabilities of different 'wood speciesfor various uses. They provide the best indexfor its use for structural purposes.5