## 3 Results and Discussions
### The Thermal Modification
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Maximum Treatment**} & \multicolumn{4}{c}{**Wood Species and Mass Loss in \%, (St.dev)**} \\ \cline{2-5}  & **Beech** & **Scots Pine** & **Stone Pine** & **Stone Pine** \\  & & & **Sapwood** & **Hearwood** \\ \hline
180 \({}^{\circ}\)C & 1.35 \({}^{\text{A}}\) & 1.33 \({}^{\text{A}}\) & 1.34 \({}^{\text{A}}\) & 9.67 \({}^{\text{BE}}\) \\  & (0.08) & (0.10) & (0.20) & (2.84) \\
195 \({}^{\circ}\)C & 3.37 \({}^{\text{A}}\) & 2.95 \({}^{\text{A}}\) & 2.99 \({}^{\text{A}}\) & 15.03 \({}^{\text{C}}\) \\  & (0.38) & (0.20) & (0.38) & (3.99) \\
210 \({}^{\circ}\)C & 10.73 \({}^{\text{BG}}\) & 5.74 \({}^{\text{D}}\) & 6.73 \({}^{\text{DF}}\) & 16.70 \({}^{\text{C}}\) \\  & (1.27) & (0.51) & (0.77) & (1.40) \\
220 \({}^{\circ}\)C & 11.47 \({}^{\text{B}}\) & 8.67 \({}^{\text{EF}}\) & 9.06 \({}^{\text{EG}}\) & 20.60 \({}^{\text{H}}\) \\  & (0.74) & (0.51) & (0.50) & (6.42) \\
240 \({}^{\circ}\)C & 26.27 \({}^{\text{I}}\) & 15.75 \({}^{\text{C}}\) & 19.56 \({}^{\text{H}}\) & 24.86 \({}^{\text{I}}\) \\  & (1.93) & (1.57) & (2.30) & (0.97) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Wood mass loss for the different temperatures and different wood species, and Tukey’s significant difference among the mean values. Mean values that share the same letter are not statistically different. Figure 3: Correlation between thermal modification temperature and color change, considering only the L\({}^{*}\) coordinate for each species. Further details emerged from the analysis of the mass increase of the thermally modified samples when continuously exposed to an atmosphere of high (98 \(\pm\) 2%) relative humidity (Figure 4A-E). As described in detail in the literature [36; 45], the hygroscopicity of all wood species decreased continuously with the increase of the maximum treatment temperature. The heartwood of the stone pine showed the lowest hygroscopicity, except for the modification at 210 \({}^{\circ}\)C, where it showed the same hygroscopicity of beech wood. The resin exudations, discontinuously covering the stone pine heartwood with a mostly water-repellent layer (Figure 2), explain its lower hygroscopicity. The results are consistent with the high hydrophobic behavior of stone pine heartwood found by [PERSON], et al. [19]. Remarkably, the sorption behavior of stone pine sapwood was comparable to that of Scots pine, except for the treatments at 180 and 195 \({}^{\circ}\)C, where their sorption curve did not exactly coincide. The curves overlapped perfectly at the treatment temperatures of 210, 220, and 240 \({}^{\circ}\)C.  
The comparison between the physical parameters after heat treatments makes the sapwood of stone pine an interesting material that has no specific disadvantages compared to the sapwood of Scots pine. Figure 4: Relationship between maximum heat treatment temperatures and water absorption from ambient air for samples placed above water in a glass chamber (RH = 98% \(\pm\) 2%): 180 \({}^{\circ}\)C (**A**), 195 \({}^{\circ}\)C (**B**), 210 \({}^{\circ}\)C (**C**), 220 \({}^{\circ}\)C (**D**), 240 \({}^{\circ}\)C (**E**).