The ageing of materials is an irreversible, in-time occurring complex phenomenon, which affects both wood surfaces and the coating materials. This paper focuses on the light-induced natural ageing of wood-coated surfaces in indoor conditions. Two wood species: European maple (Acer pseudoplatanus) and European walnut (Juglans regia) and two types of waxes: bees wax and Chinese wax were employed in the experiments presented in this paper. Uncoated and coated wood samples were exposed to the natural sunlight filtered by window glass in a simulated indoors natural ageing test for a total period of 7 years. Colour measurements in the CIE-Lab system and FTIR-ATR investigation were employed to evaluate the ageing phenomena. The uncoated wooden samples underwent progressive colour changes perceived as darkening for European maple and lightening for European walnut, corresponding to total colour differences values (ΔE) after 7 years of exposure of 12.54 and 11.66, respectively. Coating of wood samples with the two types of waxes differently influenced the total colour changes for the two wood species: reduced colour changes corresponding to ΔE values of 4.79–6.44 were determined for European maple, whilst increased colour changes corresponding to ΔE values of 13.80–20.83 were determined for European walnut. FTIR analysis highlighted different surface chemistry changes for the uncoated and wax-coated wood samples.

Subfossil oak (SO) wood material, originating from three different buried trunks discovered in recent years by excavations in riverbanks on Romanian territory, was analysed in this research. Aged oak recovered from constructions (AO_C) and recent/new oak wood material (NO) were also investigated to provide comparative data for the SO. The oven-dry density and the basic density, the total volumetric and linear swelling and shrinkage coefficients and the compression strength parallel to the grain were the selected physical and mechanical properties considered. The experimental results showed a lower density of SO compared to NO and AO_C tested by up to about 19–20%, alongside a trend of increased dimensional instability, with variability among the tested assortments. The compression strength parallel to the grain was reduced by 19–31% compared to NO. The properties of AO-C were closer to those of NO, but differences between wood materials from different sources and of different ages were registered. A positive linear correlation was found between compression strength parallel to grain and the basic density for all types of material and assortments tested. These comparative results have to be considered by designers and engineers in the valorisation of SO in furniture design and other applications.