EFFECT OF UV RADIATION ON CHANGE IN COLOR OF STEAMED BEECH WOOD

Abstract

The wood of the beech (Fagus Sylvatica L.) was steamed with a saturated steam-air mixture at a temperature of t = 95°C, or saturated steam at t = 115°C and t = 135°C to obtain a pale pink, red-brown and rich brown-red color. Subsequently, samples of unsteamed and steamed beech wood were irradiated with a UV lamp in a Xenotest Q-SUN Xe-3-HS after drying in order to test the color stability of steamed beech wood. The color change of the wood surface was evaluated by means of measured values on the coordinates of the color space CIE L*a*b*. The results show that the surface of unsteamed beech wood as well as steamed beech wood with a steam-air mixture at a temperature of t = 95°C and saturated steam with a temperature of t = 125°C darkened and turned brown to a brown-yellow color due to UV radiation. The deep brown-red color of the surface of beech wood steamed with saturated steam with a temperature of t = 135°C brightened to a brown-yellow color similar to the color of unsteamed beech wood. The analysis of the changes in the color space CIE L* a* b* shows that the greater the darkening and browning of the beech wood by steaming, the smaller the changes in the values of ∆L*, ∆a* ∆b* of the steamed beech wood caused by UV radiation. The positive effect of steaming on UV resistance is evidenced by the decrease in the overall color difference ∆E*. While the value of the total color difference of unsteamed beech wood caused by UV radiation is ∆E* = 15.3, for beech wood steamed with a saturated steam-air mixture at t = 95°C it decreased to ∆E* = 9.5, which is a decrease of 37.9%, for steamed beech wood steamed with saturated steam with temperature t = 115°C is ∆E* = 6.2 which is a decrease of 59.4% and for steamed beech wood steamed with saturated steam with temperature t = 135°C is ∆E* = 4.5 which is a decrease of 70.5%.