WOOD RESEARCH Volume 68, Number 4, 2023
Ladislav Dzurenda and Michal Dudiak

COLOR DIVERSITY OF BEECH WOOD WITH A FALSE HEARTWOOD IN THE COLOR SPACE CIE L*a*b*

The color of the false heartwood of Fagus sylvatica L. perceived by the human eye is in a wide range of shades from light brown-yellow to red-brown. The article analyzes the color in the color space CIE L*a*b* of dry wood of the false heartwood type: round, flame, star and marble. The color of the wood was measured with a colorimeter Color reader CR-10. The most colorful is the wood marble with a false heartwood. The results of statistical processing of the measured color values of dry beech wood, marble false heartwood on a planed surface identify it with values on the lightness coordinate L* = 65.2 ± 6.9 and on the chromatic coordinates: red color a* = 13.2 ± 2.3 and yellow b* = 19.2 ± 1.9. The most homogeneous in color is the color of the ring wood of the false heartwood with the coordinate values: L* = 63.7 ± 3.1; a* = 12.6 ± 1.7 and b* = 20.1 ± 1.6. The color diversity of the darkness and yellow-brown-red shades of the wood of the false heartwood is numerically quantified by the values of the total color difference ΔEsx* = 3.9 – 7.5. The presented values of the color of false heartwood beech complement the knowledge about the color of false heartwood and by defining the boundaries of color in the color space CIE L*a*b*, they create space for designers to model the color diversity of compositions and construction-joinery products made of sapwood and false heartwood beech

WOOD RESEARCH Volume 67, Number 3, 2022
Ladislav Dzurenda and Michal Dudiak

Effect of UV radiation on change in color of steamed beech wood

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 ΔL*, Δa* Δb* 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 ΔE*. While the value of the total color difference of unsteamed beech wood caused by UV radiation is ΔE* = 15.3, for beech wood steamed with a saturated steam-air mixture at t = 95°C it decreased to ΔE* = 9.5, which is a decrease of 37.9%, for steamed beech wood steamed with saturated steam with temperature t= 115°C is ΔE* = 6.2 which is a decrease of 59.4% and for steamed beech wood steamed with saturated steam with temperature t = 135°C is ΔE* = 4.5 which is a decrease of 70.5%.

WOOD RESEARCH Volume 66, Number 1, 2021
Ladislav Dzurenda and Michal Dudiak

Cross-correlation of color and acidity of wet beech wood in the process of thermal treatment with saturated steam

The paper presents changes in the color and acidity of Fagus sylvatica L. in the process of heat treatment of wood with saturated water steam in the temperature range t = 105 – 135°C during τ = 3 to 12 hours. The light white-gray color of beech wood with a yellow tint changes on the pale pink, red-brown to a brown-red color in the heat treatment process. The color changes of beech wood expressed in the form of the total color difference are in the range of values ΔE* = 1.97 – 26.85. Due to the hydrolysis of hemicelluloses, the acidity changes in the process of thermal treatment of wet beech wood. Decrease in acidity of beech wood in the range of temperatures t = 105 – 135 °C and time τ = 3 – 12 hours is in the range of pH values = 4.9 to 3.4. The dependence of the total color difference ΔE* on the change in acidity of beech wood is described by the polynomial of function II. degree. The above knowledge is a suitable tool for evaluating the degree of change in beech wood color in the technological process based on the change in pH of wood.