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A fast and economic method to produce grey wooden surfaces for decking and cladding: preliminary results
2009 - IRG/WP 09-40474
Uncoated wood is commonly used in France for cladding and decking to minimise maintenance. However wood surfaces progressively turn grey due to exposure to sunlight and water. This grey colour develops after several months depending on the wood species and the exposure: in the northern hemisphere surfaces facing south and west are most exposed and turn grey more rapidly than those facing north and east. The result is unfortunate differences in the appearance of the building which obviously is not appreciated by the end-users and which leads to a negative image of the wood material. As a consequence of this some architects would like to have grey wood right from the beginning of the construction. Producing grey wood using artificial weathering devices or natural weathering exposure is possible but too expensive and too long. In this project the idea is to develop a non-film forming coating whose colour is similar to the grey appearance produced by the natural weathering. This coating must be durable enough just to allow a soft transition between its own degradation and the development of the grey colour produced by the natural weathering.
L Podgorski, V Georges, I Garmendia, B Sánchez Sarachu

Properties of Iron (II) Sulphate treated Norway Spruce
2022 - IRG/WP 22-30765
Exterior wood is exposed to various environmental factors that cause weathering. Weathering is important primarily from an aesthetic standpoint. However, not all parts of the building are equally susceptible to weathering. Parts exposed to moisture will discolour faster than protected parts, such as wood under roof overhangs. To achieve fast and uniform artificial greying, a surface treatment with iron(II) sulphate can be used, similar to natural greying. In this study, we investigated the influence of boric acid and quarterly ammonium in combination with a solution based on an iron (II)sulphate-based solution. We treated spruce samples with different concentrations of iron(II)sulphate and biocides. After treatment, decay and water performance tests were conducted. From the test results, the wettability factor kwa and the inherent resistance factor kinh were determined. Both factors were used to calculate the resistance dose (DRd) according to the Meyer-Veltrup model. The samples were also exposed outdoors. During exposure, colour changes and iron leaching were monitored. The results show that the addition of biocides has no effect on the rate of colour change and the final colour. However, it should be noted that after only one week of exposure, 40% of the iron had leached from the surface. The addition of biocides has a positive effect on the durability of the treated wood, regardless of the low retention of the preservative solutions.
B Lesar, M Humar, M Škamlec