The objective of this study was to evaluate the glossiness of black alder wood (Alnus glutinosa L.) samples coated with two varnish types as a function of exposure to dry heat and artificial aging. The chemical resistance of the coated samples to cold liquids was also evaluated. Based on the findings in this work, it appears that the varnish types and their structural differences influenced the overall glossiness of the coated samples. The UV varnish exhibited higher gloss values than those coated with the water-borne product within the range of silky gloss and silky matte grades. The heat exposure influenced the surface glossiness of the UV-coated samples more than the samples coated with water-borne varnish. The overall gloss values of the samples decreased with the exposure time to artificial aging, resulting in no layer cracks. The cold household liquids left less visible traces on the surfaces and alcohol was found to be the strongest agent. This study could have practical applications in the furniture industry to produce value-added furniture units according to their specific conditions of indoor use.

Some Coating Properties of Black Alder Wood as a Function of Varnish Type and Application Method

In this study the properties of plywood manufactured from densified and non-densified veneer sheets and alternate layers of such veneers with and without densification using low amount of adhesive as a function of densification temperature and wood species were investigated. The plywood panels were made from rotary-cut birch and black alder veneers using urea-formaldehyde (UF) adhesive. Veneer sheets with thickness of 1.5 mm were subjected to the thermal-compression at three different temperatures while keeping constant the pressure during a same time span. Five-layers plywood panels were produced using a constant hot-pressing schedule using different amounts of glue spread as a function of the plywood type; such as plywood made from non-densified (80 g/m²) and densified (60 g/m²) veneers only; and combination of them (70 g/m²). The bending strength (MOR) and the modulus of elasticity (MOE) along with the shear strength of the plywood samples for bonding class 1 (dry conditions) have been determined. As expected bending strength of the plywood samples increased with the increasing in density. The increase of veneer densification temperature resulted in a gradually decrease of MOR; MOE and shear strength values for the plywood panels made of densified veneers and mixed panels of both species. The temperature of 150 °C for veneer densification seemed to be enough to achieve enhanced bending and bonding properties. All plywood panels in this study were manufactured using reduced glue consumption and they presented satisfactory properties performance for indoor applications.

The objective of this study was to optimize the sanding and coating processes of black alder wood to promote and support its use in furniture manufacturing. Two criteria have been applied for process optimization, namely, the minimum surface roughness of the samples and power consumption during sanding as a function of various sanding systems. The surface roughness of the sanded specimens and the power consumption during sanding strongly depends on the grit size used. Two eco-varnishes were applied to the samples by spraying. Moreover, the effect of the surface preparation and varnish type on the coating properties expressed by the varnish layer adherence to the substrate and surface glossiness was evaluated. For better glossiness values, the UV-cured varnish was preferred. The sanding with a grit sequence of 60, 120, and 150 grit size abrasives was found to be optimal when applied to black alder wood, and it is recommended to obtain performant UV-coated wood surfaces for furniture products.