THE EFFECT OF OUTDOOR WEATHERING OF THERMALLY MODIFIED SPRUCE AND PINE WOODS ON THEIR SURFACE PROPERTIES
Keywords:
spruce , pine, thermowood, weathering, colour, gloss, roughness, mould resistanceAbstract
Products from thermally modified wood used outdoors should be stable against sun, rain, wind, and biological agents. The effect of 1- to 24-month outdoor weathering of the Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) thermally modified woods “Thermo-D produced in Oy Lunawood Ltd Finland” (TWs) on their selected surface properties – colour, gloss, roughness, and mould resistance is analysed in the paper. With prolonged weathering, the surfaces of both Thermo-D wood samples lost their original yellow-red shadow. They continuously turned greyer – in the CIE L*a*b* colour system, they obtained greener and bluer colours, together with the logarithmic increase in the total colour difference ΔE*ab. Surfaces of both Thermo-D wood samples within the first four months of outdoor weathering turned much lighter with a higher gloss. However, they got darker and matter due to adsorbing soot and dirt. Similar changes, i.e., as in the lightness and gloss, occurred in the roughness of weathered Thermo-D woods, which firstly decreased and subsequently increased with further prolongation of weathering. Moulds Aspergillus niger and Penicillium brevicompactum, in all cases, intensively attacked spruce and pine wood – natural wood, Thermo-D wood, weathered natural wood, weathered Thermo-D wood.
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