Evaluation of Discolourations of Wooden Shingles as a Function of Outdoor Exposure

The main objective of the study was to evaluate the colour changes generated by outdoor exposure on spruce (Picea abies L. Karst) samples used as shingles for the roof of a traditional Maramures gate. Additionally, samples made of oak (Quercus petraea Liebl.) have been used to simulate the gate pillar. The specimens have been treated with boiled linseed oil and exposed to the outdoor environment for nine months under two different trial positions. The colour and moisture content changes in the samples have been periodically evaluated. Reactions of the samples from two species have been analysed considering three different variables, such as exposure time, treatment chemical, and positioning during their outdoor exposure. The samples vertically positioned showed fewer discolouration compared to those with inclined exposure. The total variation in colour increased as the length of exposure time increased. After nine months, the highest variation, based on the ΔE* values, was recorded in the category of untreated samples exposed at an angle of 60° to the horizontal, which showed values of ΔE* = 24.87 for oak and ΔE* = 31.16 for spruce, respectively. The oil treatment had a significant impact only on spruce samples having orthogonal exposure. The findings of this study have the potential to provide a better understanding of such species used for construction applications in relation to weathering.