Detection of outdoor mould staining as biofinish on oil treated wood

• An assessment method is proposed to detect outdoor mould staining as biofinish on oil treated wood.
• Biofinish formation was determined for oil treated wood exposed in the Netherlands and in some sites outside the Netherlands.
• Biofinish formation was demonstrated to be reproducible for pine sapwood impregnated with raw linseed oil.
• Olive oil supported biofinish formation, whereas biofinish formation was not detected on wood treated with stand linseed oil.

Stains on wood are often unwanted in outdoor applications, dark stain formation however is essential to the development of a new protective, self-healing and decorative biotreatment for wood. The biotreatment is based on the formation of surface covering mould staining on linseed oil treated pine sapwood during outdoor exposure. This specific stain formation is called biofinish and an assessment method is proposed in this study. Analysis of the visual stain coverage and quantification of the darkness generated useful input for the detection of biofinishes. Analysis of the microbial composition of a biofinish by PCR amplification and (Sanger) sequencing of fungal DNA sequences was appropriate for identification of Aureobasidium, as the dominant genus in several biofinishes, however our results indicate, that a more in depth, next generation sequencing method is preferred for a more elaborate biofinish assessment method. With the basic assessment method, biofinish formation was determined for oil treated wood specimens exposed outdoors in the Netherlands and some selected sites outside the Netherlands. Biofinish formation was demonstrated to be reproducible for pine sapwood, which was treated with raw linseed oil and exposed in the Netherlands. Furthermore olive oil is discovered in this study as a supportive factor for biofinish formation, regardless of the wood type, whereas biofinish formation was not detected on wood treated with stand linseed oil.