## 3 Results and Discussion
The brightness of hornbeam decreased less than that of maple. The total color differentiation between the color at the end and the beginning of the drying process was 7.3 for hornbeam and 11.1 for maple. For maple wood, the coordinate \(a^{*}\) did not change during the drying process. The change in the coordinate \(b^{*}\) was also smaller for maple than for hornbeam. The overall color difference between the compared wood species was minimal. Similarly, in [8], they dried poplar wood and differences between \(a^{*}\) values were found, but these differences decreased as moisture loss increased. The \(b^{*}\) coordinates decreased significantly during the whole drying process. For temperatures of 60 \({}^{\circ}\)C and 80 \({}^{\circ}\)C, the yellow hue values increased during drying. The present observations [8,9] showed that temperature had a much more remarkable impact on color changes than the duration of drying. These results agree with the work of [9, 10, 11], where a more remarkable effect of temperature than the time of drying on wood color change was confirmed. During high-temperature drying (120 \({}^{\circ}\)C), the color changes in the dried wood species were more pronounced. Very pronounced changes in brightness, and therefore also the color of the samples, occurred in the first 24 h of drying. In contrast to hot-air drying, during the high-temperature drying there was a change in the coordinates of the color space even after raising the temperature to 120 \({}^{\circ}\)C, where the change in the brightness of the samples (\(L^{*}\)) was visible. The values of color difference were also highest after 24 h, where a very remarkable change of color (to a different color) occurred in maple wood and the value of \(\Delta E^{*}\) was twice as high as in hornbeam wood. After raising the drying temperature to 120 \({}^{\circ}\)C, the color difference values increased. After high-temperature drying, the color difference was remarkable. Maple samples were remarkably darker than hornbeam samples. These results are also confirmed by [1,2], which state that the degradation of some chemical components of wood (hemicelluloses and lignin), depending on the wood species and the duration of action, occurs even at temperatures below 100 \({}^{\circ}\)C.  
In [9], \(L^{*}\) decreased at all treatment temperatures, indicating that the color became darker. At 170 \({}^{\circ}\)C, \(L^{*}\) decreased steadily, and the maximum decrease in lightness was approximately 48.21% after 12 h. Darkening of color was observed at 210 \({}^{\circ}\)C during the first 4 h and the darkest color occurred (\(L^{*}\) reduced by 64.23%) after 12 h.  
The total color difference between the color at the end and the beginning of the drying process was 8.7 for hornbeam and 18.9 for maple. The change of individual coordinates of the color space was similar for the compared wood species. The difference was in the coordinate \(a^{*}\), where in the first drying stage the value of this coordinate increased for maple wood, while it decreased for hornbeam. Table 4 shows the average values and basic statistical characteristics of the parameters \(L^{*}\), \(a^{*}\) and \(b^{*}\) before and after drying. The present observations are comparable with research [6,11] that was focused on the analysis of beech wood with red false heartwood (_FHW_) and mature wood (_MW_) color changes. When using high-temperature drying, it was discovered that the red false heartwood and mature wood had almost identical lightness (\(L^{*}\)) at the end of the drying process. From the measured data it can be seen that changes in the coordinates of the color space were detected in high-temperature drying (120 \({}^{\circ}\)C) of maple wood. Calculated values of standard deviation and sample variance confirmed a small variance of the measured values of the color space coordinates from the average value. Thirty measurements of \(L^{*}\), \(a^{*}\) and \(b^{*}\) coordinates were made on each sample.