THE EFFECT OF SUNLIGHT ON THE COLOR CHANGE OF STEAMED BIRCH WOOD
Keywords:
birch wood, saturated water steam, natural aging, wood color, steamingAbstract
The differences in color changes of native and steamed birch wood saturated with water steam at a temperature of t = 135 °C for a period of τ = 7.5 hours caused by the long-term exposure of sunlight to the surface of the wood in interiors for 48 months are presented in the paper. The deep brown-red color of the steamed birch wood lightened and acquired a brown shade due to the UV components of sunlight during the 48-month exposure. The degree of lightening of the color of steamed birch wood in the color space CIE L*a*b* is quantified by an increase in the values of the lightness coordinate from L0* = 59.8 to L48* = 66.5 and the yellow color chromatic coordinate from b0* = 19.2 to b48* = 24.0. On the contrary, the light white-brown color of the native birch wood darkened due to the effect of the UV components of sunlight and acquired a brown-pink color with a yellow tint. The degree of darkening and browning is quantified by a decrease in the values on the lightness coordinate from L0* = 81.1 to L48* = 68.2 and an increase in the values on the chromatic coordinates: red color a0* = 7.2 to a48* = 13.1 and yellow color from b0* = 20.0 to b48* = 25.9. The comparison of the color changes of native and steamed birch wood through the total color difference ∆E* under the influence of daily sunlight shows that the surface of steamed wood shows 45.8% smaller changes than native wood. The lower value of the total color difference of steamed wood points to the fact that steaming wood with saturated water steam has a positive effect on color stability and partial resistance to the initiation of photolytic reactions caused by UV + VIS wavelengths of sunlight.
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