Weathering of wood under indoor and outdoor environmental conditions

Abstract

This paper investigates the surface properties of 27 wood species exposed to indoor and outdoor weathering agents using above-ground test equipment for 1 year in Bursa, Turkey. For this purpose, colour changes, surface roughness and chemical composition of wood surfaces were analysed at an interval of 3 months during the exposure period. The results showed that the colour change on the wood surfaces exposed to outdoor weathering was observed during the first 3 months, and that the temperate wood species showed much more surface darkening and colour change compared with tropical wood species. In outdoor weathering, the least colour change was found in wenge as a tropical wood, and in walnut and elm as the temperate species, while the greatest colour change was in ayous and poplar. In the case of indoor weathering, iroko and cherry displayed the least amount of colour change, while the most was seen in wenge and Scots pine. Additionally, surface roughness and cracks increased with weather conditions, especially in outdoor conditions. Fourier Transform-infrared spectra revealed chemical changes, especially in carbonyl and lignin groups. Significant darkening, mould growth and crack formation on the surfaces were observed after the ninth month of outdoor weathering. However, cracks or mould formations were not observed on the samples exposed to indoor weathering; only a slight colour change was common. The study showed that the indoor and outdoor degradation agents, wood species and humidity conditions had an important role in the tested parameters.