The effective control of moulds on freshly impregnated wood
G Cofta, K Lutomski, P Jüngel
Beside natural timber it is known, that moulds can also groth at the surface of impregnated wood. This material shows “defects” like resistant dark spots or color changes and causes complaints. During the last years, the problem by moulds seems to increase.
Laboratory studies were carried out to show the effect of impregnations against moulds. Wood samples (Pinus sylvestris L.) were impregnated by vacuum process using two industrial chromium-free copper based wood preservatives and a CCA-salt. Furthermore fungicides of isothiasoles as “mould-protection-chemicals” were added to the impregnation solutions. To consider an aging effect of this chemicals the modified solutions were stored at temperatures of 20°C or 40°C for 7 days. Direct after impregnation or after 4 weeks of conditioning the samples a mixture of moulds (Aspergillus niger, Penicillium cyclopium, Penicillium funiculosum, Paeciliomyces varioti, Trichoderma viride) were used to infect the impregnated material. The growth of moulds were observed after different times.
The intensity of the growth of moulds was different during the first days, but already after 10 to 14 days all samples had complete moulds at the surface. Therefore none of the wood preservatives was protecting the samples against moulds. In the case of sample impregnations using wood preservatives with additional mould-protection-chemicals a various resistance of the impregnated wood on mould infection was found. The resistance depends on the combination of the type of wood preservative and the fungicide used. Differences caused by the aging test could be observed.
It can be deduced from these results that this investigation method can help to answer questions concerning necessity, suitability and the appropriate type or content of mould-protection-chemicals in impregnation solutions.