Artificial Weathering of Contact-Charred Wood—The Effect of Modification Duration,Wood Species and Material Density |
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Authors: | Maija Kymä lä inen,Tinh Sjö kvist,Jakub Dö mé ny,Lauri Rautkari |
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Affiliation: | 1.Department of Bioproducts and Biosystems, Aalto University, P.O. Box 16300, FI-00076 Aalto, Finland; (J.D.); (L.R.);2.Department of Forestry and Wood Technology, Faculty of Technology, Linnæus University, SE-351 95 Växjö, Sweden;3.Department of Wood Science and Technology, Faculty of Forestry and Wood Technology, Mendel University in Brno, Zemědělská 3, 613 00 Brno, Czech Republic |
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Abstract: | A relevant issue with charred exteriors is the inconsistency of the result, which makes service life predictions complicated. Contact charring enables the creation of a very evenly modified surface with accurate control of temperature and modification time, but the weathering properties are questionable. This paper evaluated the effect of the modification time relative to char layer and transition zone thickness, wood species and material density in an artificial weathering test. The results revealed higher color stability in connection to longer modification time, but also an increase in the cracked surface area. Cracking was heavily dependent on the modification regime and increased with increasing char and transition zone thicknesses. Dense spruce had the highest color stability with the most severe modification regime, but char layer thickness varied more than on other wood types. Furthermore, species-dependent cracking patterns affected the final result as the small-scale flaking experienced by birch increased the washing off of char. It is likely an even higher modification temperature with a shorter modification time is needed to produce sufficient weathering resistance suitable for exterior uses. |
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Keywords: | artificial weathering carbonization contact charring surface modification wood wood modification |
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