Colour measurement technology is found to be feasible for characterization of the property changes of thermally modified timber (TMT). In opposite to time-consuming and expensive laboratory tests a non-destructive test represents an improvement for the manufacturer of TMT. Therefore the aim of this study was to develop a method which allows sorting the different treatment intensities after the manufacturing process separately from each other, so as to help the manufacturers to ensure product quality. For TMT of beech wood a correlation of process-related decrease in mass to L*b*-colour-values was proved. Furthermore, linked to higher treatment intensities the fungal-related mass loss of TMT decreased. Fungal tests with Trametes versicolor indicated that the individual changes of the specimens need to be considered during the sorting of the durability classes. Therefore the development of the method of quality assurance is not directed to the production batches and thus determined averages, but by correlations of the parameters. With a selected model, parameters, e.g. durability, were calculated as a function of colour values. But the prediction of durability classes of TMT, based on colour values was feasible only to a limited amount of samples. The prediction of a durability class 2 or 1 seems to be feasible for treatment intensity of temperatures ≥ 220 °C.

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