Testing the Predictability of Preservative Treatment of Wood

An apparatus was developed in an attempt to predict the treatability of full-sized wooden members prior to preservative pressure impregnation. This simple, rapid, and non-destructive method was based on assumed comparability of penetration of air, under pressure, from the surface to the interior of wood, and that of preservative liquids during pressure treatment. The permeability of Douglas-fir heartwood specimens 2" X 4" 47" in length was determined in the transverse and longitudinal directions using a surface-contact, non-steady-state method with applied air pressures of 81 and 158 psig. The specimens were then impregnated with 35% PCP-petroleum oil solution using a full-cell process. The correlations between specimen permeability, äs measured by pressuredrop in an air reservoir, and both gross and assayed retention were found to be poor, but analysis has suggested further modifications in the apparatus that may give more satisfactory results.