PREHEATING GREEN BOARDS OF MOUNTAIN ASH (EUCALYPTUS-REGNANS F MUELL) .2. RELATIONSHIPS AMONGST PROPERTIES

Analysis of data for shrinkage, basic density, moisture content, level of saturation and green density in board sections of control and pre-heat treated wood of mountain ash showed positive relationships between internal checking and basic density, green density and level of saturation; this indicated that disposition and width of earlywood and latewood bands was not the only means of anticipating this defect. Positive relationships also found between change in internal and surface checking after preheating and basic density indicated that low density material responded best to pre-treatment. Relationships with properties for external and total shrinkage were generally similar to that reported previously, i.e. positive with respect to moisture content, level of saturation and green density, and negative with respect to basic density. Significant relationships between all shrinkages and green density, coupled with ease of measurement, suggested potential for this property as a shrinkage predictor; however, variation in relationships among trees foreshadowed limitations for this application. Relationships among external shrinkage, internal checking and surface checking were all significant and positive, indicating that one type of shrinkage did not occur at the expense of another. It was shown that number of internal checks (N(i)) was positively correlated to shrinkage of internal checking (S(vi)) and that DELTAN(i) and DELTAS(vi) were similarly related.