A technique for determining the efficacy of wood preservatives for partially treated timber

A technique is described for determining the efficacy of wood preservatives either for certain wood species where a full penetration cannot be achieved by normal vacuum-pressure methods or for more permeable species to look at efficacy of treated zone in preventing decay of an untreated core. Both sapwood and heartwood planks of spruce (Picea abies) and pine (Pinus sylvestris) were treated by CCA using different treatment schedules. After a preservative fixation period the planks were cross-cut into small blocks, end sealed with flexible epoxy resin and conditioned in a constant climate room. The preservative penetration was measured from each individual block and the retention by analysing replicate blocks from each individual plank. The test method used was a modified EN 113 with Coniophora puteana and Poria placenta as the test fungi. Series of replicate blocks were harvested after 9, 16 and 26 weeks. No significant decay was found in treated blocks, but untreated controls showed weight losses comparatable with previous results with the conventional EN 113 method. Further development work is still needed, but it is considered that the present method has potential for the approval of preservatives and treatments for refractory species.