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Visual properties of spruce wood coated with lacquers, changed under impact of UV radiation in indoor conditions

Kúdela J., Sikora A., Svocák J.

Annals of Warsaw University of Life Sciences - SGGW. Forestry and Wood Technology

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2018

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No. 103

84--89

EN

This work evaluates accelerated-ageing-induced effects imposed on colour stability of spruce wood coated with colourless polyurethane lacquers proposed for surface treatment for wood artefacts intended for the indoor. There were explored the colour and gloss variations at an accelerated ageing process representing 500 hours. Simultaneously, there was also examined the protective performance of pre-treatment with a UV radiation absorbent agent. The experimental results give evidence that in all cases, during accelerated ageing process, the influence of UV radiation on photo-degradation of the surface-treated spruce wood was significant. The tested lacquers, however, manifested diverse degrees of protective efficacy against UV radiation-induced effects to the wood surface in indoor conditions. The colour stability was found poorer for the surface treatment with lacquers without protective agents against UV radiation. The UV protective substance admixed into the coating material had an obvious decelerating effect on the photo-degradation in the surface-treated wood, but this degradation had not been inhibited absolutely. In all cases, the lightness decreased and the coordinates a* and b* increased. The result was that the treated wood surface attained yellow-brownish hue of various intensities. On the other hand, the gloss quality was preserved in all treatments.

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Beech wood discoloration induced with specific modes of thermal treatment

Kúdela J., Andor T.

Annals of Warsaw University of Life Sciences - SGGW. Forestry and Wood Technology

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2018

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No. 103

64--69

EN

This work´s study subject is beech wood surface discoloration induced by thermal treatment and by thermo-hydro-mechanical treatment. In the first case, the test specimens were exposed to a 3h heat treatment at temperatures of 160, 180 and 200 °C. In the second experiment, the specimens were pressed (thermo-hydro-mechanical treatment) under various pressing conditions. There was investigated the influence of several pressing parameters (initial moisture content in specimens, pressing time and temperature, compression degree) on wood discoloration. The two treatments caused significant shifts in the colour coordinatesL*, a*, b* with increasing temperature and prolonged treatment time:the lightness decreased significantly, with the a*coordinate shifting to red and the coordinate b* to yellow. These shifts were also reflected in the total colour difference E. The discoloration of the beech wood surface was dependent on the heat energy amount and on its supplying mode, and also close associated with absorbance capacity of the main wood components and with variations in the chemistry of these components.

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Deformation of beech wood – the sources and their identification before beech logs processing

Kúdela J., Gryc V., Tóth V.

Annals of Warsaw University of Life Sciences - SGGW. Forestry and Wood Technology

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2014

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No. 87

121--125

EN

Longitudinal buckling is a very serious problem in production of solid wood panels assembled of beech lamellae joined alternatively breadthwise and longwise into large-sized blocks. The aim of our work was to identify the main factors causing misshaping of beech dowels in solid wood panels production, with the primary focus on identification of reaction tension wood in dowels and logs. According to our results, the most common source of longitudinal buckling of beech dowels was the presence and non-uniform distribution of tension wood in them. The tension wood occurrence in logs is possible to predict with a considerable confidence based on eccentric pith presence. The tension wood presence and distribution over the cross section are possible to identify if the cross-cut surface has been milled and its moisture content reduced under FSP. The tension wood can be discerned through its lighter hue and pearlescent-white gloss.