Effect of weathering on thickness, colour and chemical composition of one-side charring surface of tropical woods

Physical, mechanical and chemical properties of one-sided surface charring have been studied for tropical species. However, there is no information regarding the behaviour of surface charred wood under weathering for these species. The objective of this study was to evaluate the change in charring thickness, colour and chemical composition analyzed by Fourier transform infrared spectroscopy (FT-IR) of one-sided charred wood of Cupressus lusitanica, Gmelina arborea, and Tectona grandis under natural weathering for one year. The results revealed that all three species experienced a decrease in charring thickness after weathering. No visible mould, minimal cracking, and little to no detachment of the charred surface were observed. Weathering exposure increased both redness and yellowness tonalities. Not significant differences in carbon content were found between the one-sided charred and weathered samples of G. arborea and T. grandis. The FT-IR spectrum showed a reduction of signals associated with water (3500–2900 cm⁻¹) and the wood's organic matter (600–1800cm⁻¹) in charred wood. After weathering, an increase in the intensity of these signals was observed, particularly in C. lusitanica and T. grandis. One-sided charred surface of G. arborea was less affected, while the charred surfaces of C. lusitanica and T. grandis were more affected.