Color Change Analysis of Wood Materials Treated with Different Varnishes: A Comparative Study

Abstract

Aim of the study: This study examines the overall color change values from applying water-based, polyurethane, and acrylic varnishes on newly prepared and naturally aged wood materials.
 Materials and methods: The Turkish woodworking industry commonly selects oak (Quercus petrea L.), chestnut (Castanea sativa M.), and scotch pine (Pinus sylvestris L.) as the preferred wood type for preparing test samples. A total of 360 test samples are prepared for the experiments. The color difference (ΔE*) between two colors is measured using a Minolta CR-231 color measurement device, following the principles outlined in ASTM-D 2244. 
 Main results: On the C.I.E. Lab* color plane, a higher ΔE* indicates a more significant difference between the compared colors. Among the wood type, oak exhibited the highest color change (ΔE*), while chestnut displayed the lowest. Fresh wood materials showed higher color change values (ΔE*) than naturally aged wood materials. The radial section direction also is showed higher color change values (ΔE*) than the tangential section direction.
 Research highlights: Regarding varnish type, acrylic varnish indicated a minor color change, followed by polyurethane and water-based varnishes, respectively. Acrylic varnish is recommended for studies with minimal color change and for preserving the wood material's natural color.