A series of methods for determining penetration of wood preservatives into the wood structure have been developed for either quality control (QC) or research and development purposes. QC methods range from monitoring the solution uptake, applying colour indicators or sampling specific wood samples followed by wood acid digestion/atomic absorption spectroscopy (AAS) or solvent extraction/chromatography analysis. Several standard methods for penetration analysis were developed by various standardization groups (e.g. AWPA, CEN). They are mostly used in correlation with a specific wood preservative system. Additional analytical tools are necessary for detailed penetration studies, especially during product development of a new wood preservative. Sufficient penetration of the active components into the wood structure plays an essential role in determining the service life of treated wood. Depending on the desired end use (use class) of the treated wood component, different penetration requirements apply. Therefore studying and optimizing the penetration characteristics of new wood preservatives must be an integral part during their development. Furthermore monitoring that the penetration requirements are fulfilled in the wood treatment process is an important aspect to ensure the quality of treated wood products. The aim of this study was to review several methods currently employed to determine the penetration of the wood preservative actives e.g. colour indicators, solution uptake of treated wood, direct gradient studies by wood acid digestion/atomic absorption spectroscopy or solvent extraction/chromatography analysis, and microbiological studies using different types of fungi. Factors which can impact on the outcome from these methods are being discussed based on some “model” wood preservative systems.

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