The effect of UV radiation in Xenotest 450 on the colour of steamed beech wood during the process of simulated ageing

The effect of UV radiation in Xenotest 450 on the colour of steamed beech wood during the process of simulated ageing .The aim of the paper is to present the changes in colour of steamed beech wood in the pocess of simulated ageing in Xenotest 450. Red-brown colour of beech wood with the coordinates of L* = 62.6 ± 2.8; a* = 10.9 ± 2.3; b* = 17.1 ± 1.3 in the CIE L*a*b* colour space resulted from the mode of colour modification of wood with saturated vapour with the temperature of t = 120 ± 2 oC for τ = 6.5 hours. The surface of samples after drying to the moisture content of w = 12 % and planing was irradiated in Xenotest 450 with xenon gasdischarge tube by UV radiation with the wave length of 340 nm. Accelerated ageing experiment ran in exposure period A1 for seven days. Simulated ageing of thermally treated beech wood showed that due to UV radiation, the wood surface is turning pale and brown. The change in the lightness coordinate by the value of ΔL* = + 6.7 shows the rate of change in the surface lightness and the changes in the values of chromatic coordinates of red colour by the value of Δa* = - 0.1 and yellow colour by Δb* = + 12.3 shows the rate of getting brown. Therefore the hue angle increases from h*ab = 57.5 ° to h°ab = 69.8 °. The value of the total colour difference resulting from the process of ageing is ΔE* = 14.5.