Many timbers contain chemical extractives that undoubtedly play a key role in the timber's natural durability. Opepe (Nauclea diderrichii) and padauk (Pterocarpus sp.) are both very durable timbers (class 1), yet they are described as being moderately permeable. This suggests the presence of biocidal chemicals within these timbers, rather than simple blocking agents. Initial trials on the location and role of the extractives are presented, including the changes in bioresistance of the extracted timber to laboratory pure strains of brown and white rot fungi. The extractives responsible for the enhanced durability are probably located within the cell wall and require polar solvents such as methanol or acetone to remove them. These solvents will be used in further extractive studies. This project forms part of a wider program of research concerned with novel approaches to wood preservation, based upon a detailed understanding of wood chemistry. The overall objective is to develop environmentally benign techniques for timber preservation.

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