Radiata pine (Pinus radiata) wood veneers glued to solid wood hacking strips were exposed outdoors at 45° north-facing for one year and then examined by light microscopy (LM) and transmission electron microscopy (TEM). As expected, the exposed wood surfaces were colonised by a variety of microorganisms; however, wood decay was not observed. Ultlaviolet (UV light) radiation and water were the main factors responsible for changes such as discolouration and the altered microstructure of wood cell walls which led to their disintegration. Cell wall discolouration observed under LM is due to UV light-induced breakdown in lignin, which may eventually disappear completely from some areas of the wood cell wall. The resulting increase in cell wall porosity was observable in the TEM. TEM was also used to identify the cause of failure of an oil-baised stain which was applied to one set of veneers before exposing them outdoors. The observations underscore the potential udefulness of a combined light and electron microscopy approach to study wood weathering.

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