Effect of Drying Oil on Properties of Traditional Painted Coatings

This study examines the effects of drying oils—Tung and linseed—on the properties of traditional polychrome coatings applied to wood. Samples prepared with cinnabar, malachite green, yellow ochre, and azurite pigments were analyzed using colorimetric, gloss measurements, surface roughness testing, adhesion strength, and SEM imaging. The results show that Tung oil generally enhances gloss by over 20% and provides superior adhesion, consistently achieving an adhesion grade of 0 (no peeling) across all pigments. Linseed oil, although effective at higher concentrations, displayed more variable adhesion, particularly with blue and yellow pigments. Surface roughness measurements revealed that higher oil content (6:4 ratio) reduced roughness, achieving smoother finishes with Ra values as low as 2.36 μm for Tung oil. SEM analysis confirmed that Tung oil yields a smoother and more even pigment distribution compared to the rougher, clustered morphology in linseed oil samples. These findings underscore the importance of oil type and concentration in achieving desired esthetic and durability outcomes in restoration work.