Determination of Optical Properties of Ovangkol (Guibourtia ehie) Wood Treated with Oxalic Acid and Hydrogen Peroxide

Abstract

Ovangkol wood is a valuable species in woodworking industries, especially in the furniture sector. Bleaching processes alter the color of the wood. In this research, changes in certain surface properties [whiteness index (WI*), glossiness, and color parameters (lightness (L*), red (a*) color tone, yellow (b*) color tone, chroma (C*) value, and hue (ho) angle)] were investigated upon the application of two different bleaching chemicals [oxalic acid (C2H2O4) and hydrogen peroxide (H2O2) + sodium hydroxide (NaOH)] on the surfaces of ovangkol (Guibourtia ehie) wood. With the chemical C2H2O4, increases were observed in the WI* ║ direction and in all color parameters. In addition, with the NaOH + H2O2 solution, increases were obtained in the L* and ho values, while decreases were observed in the a*, C*, and b* parameters. When employing the C2H2O4 chemical, the ∆E* value measured at 4.25, whereas treatments involving solutions prepared with H2O2 + NaOH yielded a ∆E* value of 13.14. Positive ∆L* values were observed with the use of both chemicals. Conversely, while the ∆a*, ∆b*, and ∆C* values showed positivity with the C2H2O4 chemical, they exhibited negativity when using the NaOH + H2O2 solution. Glossiness values decreased at both 60 and 85 degrees, irrespective of whether they were measured parallel or perpendicular to the fibers, following the application of both bleaching agents on the wooden surfaces.