*Article* **Comparison of Exterior Coatings Applied to OakWood as a Function of Natural and Artificial Weathering Exposure**

**Eliška Oberhofnerová 1, Kristýna Šim ˚unková 1, Ondˇrej Dvoˇrák 1, Irena Št ˇerbová 1, Salim Hiziroglu 2, Pˇremysl Šedivka 1 and Miloš Pánek 1,\***


Received: 13 November 2019; Accepted: 14 December 2019; Published: 16 December 2019

**Abstract:** Artificial weathering can significantly reduce the testing time needed for proving coating durability, nevertheless its reliability is still not thoroughly proven. In this study, eight di fferent transparent and pigmented coating systems, namely oil, acrylate, alkyd and urethane alkyd were evaluated through natural and artificial weathering tests on oak samples by measuring colour, gloss and surface wettability and by macroscopic and microscopic evaluation. The oil coatings performed well in wood colour stability evaluations, while the best gloss and wettability change results were noted for acrylate coatings. Pigmented coatings were characterized by significantly lower colour changes than transparent ones. The gloss and wettability changes were more sensitive to coating disruption than to total colour changes of coated wood associated with chemical changes in wood. The findings in this work showed that values of gloss changes and surface wettability for all types of coatings exposed to artificial and natural weathering resulted in significant di fferences from each other. The data obtained by artificial weathering method provide basic results of coatings durability and, ideally, natural weathering should be performed at the same time to support the results from laboratory tests by exposing wood under real conditions.

**Keywords:** artificial weathering; coatings; durability; natural weathering; oak wood
