## 3 Results and Discussion
### Aesthetic Durability of the Additive in Challenging Environments  
Because tea extract's color durability is sensitive to outdoor environmental factors [66; 67], the samples underwent characterization tests in harsh conditions. Figure 5 illustrates the observable aesthetic alterations of the coatings after exposure to UV-B radiation. Figure 5a depicts the progression of gloss values throughout the test, while Figure 5b accentuates alterations in color. Additionally, both graphs feature curves representing the untreated wood substrate, serving as a benchmark material for comparison. The narrow error bars once again affirm the reproducibility of both the gloss and colorimetry measurements conducted. Exposing the samples to a UV-B chamber results in noticeable aesthetic alterations. The reflectance properties of pure acrylic paint tend to diminish, as demonstrated by the gloss curve of the G0 sample. This behavior, consistent with previous research [68; 69], is attributed to photodecay phenomena affecting the resin. Conversely, the samples incorporating the bio-based additive exhibit minimal changes in texture, as the wax promptly imparts opaque characteristics onto the composite coating. Furthermore, all four series of coatings, along with the wood substrate, exhibit a distinct color change represented by \(\Delta\)E (Figure 5b). Poplar wood, in particular, demonstrates significant color alteration, attributed to photooxidation processes and degradation of cellulose, hemicellulose, and lignin [70; 71; 72]. The gradual increase in \(\Delta\)E values observed in sample G0 is attributed to a slight degradation of the wooden substrate [73], not entirely shielded by the transparent coating. This phenomenon has been previously documented in a study [74], highlighting the inability of paints to entirely mitigate photooxidation effects in wood, especially evident when the coating is transparent. Concurrently, samples containing the green additive display noticeable color changes, with the degree correlating to the concentration of wax-based powder. This indicates that UV-B radiation triggers aesthetic degradation of the bio-based additive. The extent of these chromatic variations is mitigated to some degree by the UV  
Figure 4: SEM micrographs of the cross-section of (**a**) sample G0, (**b**) sample G5, (**c**) sample G10, and (**d**) sample G10U. absorber in sample G10U, resulting in lower \(\Delta\)E values compared to sample G10. However, it is important to note that the chromatic degradation in sample G10U is still significant, albeit reduced. The UV absorber's impact is notable during the initial hours of exposure; however, as the test progresses, its effectiveness diminishes due to the aggressive nature of the conditions, rendering the protective component ineffective. To underscore the deterioration of the wax-based additive infused with green tea, the same powder underwent the accelerated degradation test. Figure 6 illustrates the visual changes in the additive before (left) and after (right) 48 h of exposure in the UV-B chamber. The images clearly depict a significant transformation in the appearance of the additive, with the majority of the green-yellow component from the tea extract almost completely faded. Additionally, the temperature within the chamber (60 \({}^{\circ}\)C) causes partial melting of the wax-based powder. Indeed, while rice bran wax has previously shown resilience to UV-B radiation [34], various components of green tea are notably susceptible to decay. Green tea consists of 30-42% polyphenols [75], primarily catechins [76], which are particularly prone to degradation when exposed to light and temperature [77]. Therefore, given the observed significant degradation of the bio-based additive, it becomes evident why the coatings G5, G10, and G10U exhibit distinct color changes as depicted in Figure 5b. Specifically, Figure 7 illustrates the progression of individual color coordinates of the samples during the accelerated degradation test.