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 ∆E* = 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 ∆E* 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.