Determination of optical properties of ovangkol (Guibourtia ehie (a.chev.) j.léonard) wood treated with oxalic acid and hydrogen peroxide

Ovangkol wood, an exotic wood species, is becoming valuable in the woodworking industries, particularly in the furniture sector. Bleaching treatments alter the color of the wood. In this study, changes in certain surface properties [whiteness index (WI*), glossiness, and color parameters (lightness (L*), red color (a*) tone, yellow color (b*) tone, chroma (C*), and hue angle (ho))] were investigated by applying two different bleaching chemicals [oxalic acid (C2H2O4) and hydrogen peroxide (H2O2) + sodium hydroxide (NaOH)] on ovangkol (Guibourtia ehie (A.Chev.) J.Léonard) wood surfaces. According to the results, increases in WI* in the parallel direction and all color parameters were observed with the C2H2O4 chemical. Additionally, with the NaOH + H2O2 solution, increases in L* and ho values were achieved, while decreases in a*, C*, and b* parameters were observed. When using the C2H2O4 chemical, the ∆E* value was recorded as 4.25, whereas it was determined as 13.14 for treatments with solutions containing H2O2 + NaOH. Positive changes in ∆L* values were observed with both chemicals. However, positive ∆a*, ∆b*, and ∆C* values were observed with the C2H2O4 chemical, while these values were negative with the NaOH + H2O2 solution. The glossiness values decreased at both 60° and 85° angles regardless of whether the bleaching agents were applied parallel or perpendicular to the wood fibers.