Surface Hardness of Three Types Varnish Applied to Fresh and Naturally Aged Wood

Aim of study: This study was carried out to determine the surface hardness values of some varnishes applied to the surface of naturally aged wood material. Material and methods: Acrylic, polyurethane and water-based varnish was applied to the surface of the experimental samples prepared from naturally aged and fresh Scots pine (Pinus sylvestris L.), sessile oak (Quercus petrea L.) and chestnut (Castanea sativa M.) wood materials. A total of 360 test samples, 10 for each wood type, cutting direction, age period, and varnish type were prepared then the surface hardness values of these samples were determined. Main results: As a result of the experiments, the effect of the age period on the surface hardness of the varnish layer was found to be insignificant. The highest surface hardness value in wood material was obtained in the tangential section of oak wood and the difference between oak wood and chestnut wood was statistically insignificant. As a varnish type, the highest surface hardness value was obtained in polyurethane varnish, followed by acrylic varnish and water-based varnish, respectively. In addition, the surface hardness of the varnish layer in the tangential section of the wood material was found to be higher than that of the radial section. Highlights: In cases where high surface hardness is required in the varnish layer, polyurethane varnish can be preferred. As a result of the experiments, water-based varnish with a low surface hardness value will be able to give a working performance compatible with wood material with a hygroscopic structure, thanks to its high elasticity. For this reason, wood with a high amount of dimensional change can be used to protect the material against external influences.