Mikuláš, Denis: Photodegradation of oil surface treatment of thermo-wood. Bachelor thesis, Technical University in Zvolen. Faculty of Wood Sciences, Department of Furniture and Wood Products. Thesis supervisor: Ing. Gabriela Slabejova, PhD. Zvolen: Faculty of Wood Technology, Technical University in Zvolen, 2019.This bachelor thesis deals with photodegradation of thermally treated and untreated beech and oak wood with oil and wax finish. Beechwood was thermally treated at 175 ° C for 4 hours. Oak wood was also thermally treated at 175 ° C and 195 ° C for 4 hours. Three oil and wax-based finishes have been created on both thermally treated and untreated wood. Surface treated samples were exposed to sunlight for 260 days. The surface color of the CIE L * a * b * system was measured at specified time intervals. The light stability was evaluated based on the calculated total color difference ΔE*ab. The work showed that the color changed in thermally modified and thermally untreated samples exposed in the interior. Oil-based and wax-based coating has not prevented photodegradation, and even the color of the coating film itself contributes to changing the color of wood finishes.