On the modelling of colour changes of wood surfaces

Colour has an influence on the aesthetic properties of wood surfaces, and changes in colour have an impact on each individual's perception of wood construction materials. This study examines an approach to model the discolouration of wood during natural weathering. A novel mathematical model was used to estimate colour changes of two softwoods during natural weathering. The surface colour of fir and larch samples was determined according to the CIEL*a*b* system during natural weathering over a period of one year. In order to demonstrate the value of the model, two different weathering sites were chosen. The data collected from each site was smoothed using a local regression method, and the corresponding parameters were used to generate the confidence intervals around the smoothed curves. The results show that all three colour parameters exhibit varying differences during the weathering trial. The locally weighted regression method seems to be an appropriate approach for modelling weathering effects and could be used to simulate colour change in wood in exterior applications in the future.