**4. Conclusions**

Eight di fferent transparent and pigmented coating systems were applied on oak samples and tested using artificial and natural weathering. Total colour di fference was mostly related to the lightness parameter change. Evaluation of discolouration with other criteria such as gloss, surface wettability and visual and microscopic evaluation more accurate predicted service life of coatings. Pigmented coatings had significantly lower colour changes than transparent ones, for both artificial and natural weathering. Oil coatings were more colour stable, acrylate coatings achieved the best results of gloss and wettability changes. The gloss and surface wettability changes better copy degradation and disruption of coated wood in comparison with total colour changes. Even there were some visually observed similarities in the test results of AW and NW exposed samples, this was not confirmed statistically. The Spearman rank correlation showed strong statistically significant relationship between results after artificial and natural weathering only for the gloss changes of all coatings and surface wettability and gloss changes of transparent coatings separately.

**Author Contributions:** Conceptualization and Methodology M.P.; Formal Analysis, E.O.; Investigation, K.Š., O.D., I.Š.; Writing—Original Draft Preparation, E.O.; Writing—Review & Editing, E.O., M.P., S.H.; Supervision, M.P.; Project Administration, P.Š.

**Funding:** This work was supported by the gran<sup>t</sup> "Improving of coatings durability on selected kinds of wood in the exterior applications," No. TH02020873, financed by TA CR. ˇ

**Conflicts of Interest:** The authors declare no conflict of interest.
