## 3 Results and Discussion
### Effect of Blending on the Clromatic Characteristics of WSs  
Examining the results of ANOVA for the chromatic characteristics of the studied WSs (Figure 7), a similar pattern (non-significant differences) in those produced by the natural blending and by the blending operation in each ageing technology is noted. Lightness (L*) depicts the grey scale in each colour, varying from fully transparent/bright (100%) to fully opaque/dark (0%) [66]. The WSs resulting from blending in alternative ageing technology exhibited lower lightness than those from blending in the traditional technology (62.02-64.22 vs. 79.36-84.24%), thus having more opaque/darker colour (Figure 7a). Chroma (C) corresponds to the colourfulness assessed in relation to brightness; a direct relationship exists between the intensity of the colour perceived by the human eye and the chroma [66]. The WSs produce by the alternative ageing technology showed higher chroma than those from the traditional one, regardless of the blending technology (87.70-89.73 vs. 62.11-64.91), and therefore, they had more intense colour (Figure 7a). Regarding the chromaticity coordinates, a* takes positive and negative values for reddish and greenish colours, respectively, while b* takes positive and negative values for yellowish and bluish colours, respectively [66]. All the WSs displayed a combination of reddish (a* > 0) and yellowish (b* > 0) colours that correspond to amber/orange colours  
Figure 7: Average values of chromatic characteristics of WSs from natural blending and from the blending operation in each ageing technology: (**a**) lightness and chroma; (**b**) chromaticity coordinates; (**c**) absorbance at 470 nm. Bars and circles not marked with letters indicate non-significant differences between the average values (_p_ > 0.05). (Figure 7**b**). Interestingly, considering these two parameters, the WSs are not grouped according to the blending technology, but rather as clusters of each ageing technology. Indeed, the alternative ageing technology induced a faster development of colour (higher intensities of reddish and yellowish colours) than the traditional one: a* (20.74-22.99 vs. 4.84-6.35) and b* (85.21-86.74 vs. 61.92-64.60). In addition, the absorbance at 470 nm reflects the complementary colour, brown [67]. As for the CIELab parameters, the WSs resulting from blending in alternative ageing technology had a more intense brown hue than those from blending in the traditional technology (0.65-0.71 vs. 0.30-0.33)--Figure 7c. The outcomes are consistent with those attained during the ageing of WSs from each ageing technology [14]. In the chemistry underlying the colour evolution over the WS ageing stage [14; 19], oxygen and the kind of wood play a pivotal role, which is boosted by the MOX applied to WS kept in stainless steel with wood staves inside. Under these conditions, greater extraction of phenolic compounds and furanic aldehydes from the wood, more intense reactions encompassing their precursors, and the succeeding ones, namely oxidation reactions, involving mineral elements (iron and copper), are triggered and promote a faster colour development (associated with lower lightness, higher chroma, and more intense amber and brown colours). Complementarily, the results obtained for the total colour difference (\(\Delta\)E) are in accordance with those of CIELab, showing a non-significant effect of the blending technology, as expected. The average \(\Delta\)E values of the WSs resulting from the natural blending and blending operation in each ageing technology (96.74 vs. 97.97, alternative; 67.57 vs. 68.78, traditional) differ only by about 1.5 units. This small deviation means that the WSs developed a similar colour, regardless of the kind of blending performed. Comparing the WSs from the alternative and traditional ageing technologies, higher average \(\Delta\)E values (with about 29 more units) were found in the former, pointing to a more evolved colour for the same ageing time.