Impact of different radiation forms on beech wood discolouration
This study analyses beech wood surface discolouration induced through UV radiation during an accelerated ageing process and with radiation emitted from a CO2 laser beam operating under specific settings. The results show that the extent of beech wood surface discolouration was dependent on the amount and the type of the energy delivered and on the absorption performance of the main wood components. It was observed that increasing irradiation dose caused decreasing wood surface lightness in both UV radiation and CO2 laser-produced radiation scenarios. In most cases, the values of colour coordinates a* and b* increased, and the wood surface was gradually turning dark brown. At high irradiation doses from the CO2 laser, there were recorded decreasing trends in a* and b*, and the beech surface darkened substantially (up to black). To attain purpose-oriented wood surface discolouration under specific modification modes, there is necessary to carry out thorough chemical analyses of the treated wood surface and to express quantitatively the dependence between the energy supplied, colour, adsorption capacity of the main wood components and the ongoing chemical changes.