Kiln-, Solar-, and Air-Drying Behavior of Lumber of Tectona grandis and Gmelina arborea from Fast-Grown Plantations: Moisture Content, Wood Color, and Drying Defects

Tectona grandis and Gmelina arborea are common in commercial reforestation in the tropics. However, color variations, moisture content, and drying defects are also present in dried lumber. Moisture content variations, drying defects, and color changes were evaluated in the present work for three drying methods (kiln, solar, and air drying) during three seasons (dry, rainy, and transition season) in Costa Rica. According to the results, kiln drying had the fastest drying times, regardless of the season. On the other hand, air drying had slower drying time and higher final moisture content. With regard to defects, kiln drying produced the highest number and magnitude of defects in both species, whereas air drying showed the lowest quantity and severity of defects. No variations due to the drying methods or the season were observed in check and split, though solar drying presented intermediate values in all drying defects. The seasons of the year did not present any effect on drying defects. Finally, T. grandis dried lumber is darker than green lumber, and dried G. arborea wood is clearer. In addition, there is an increase in red (a*) and yellow (L*) tonalities, and color changes (Δ E*) are considered perceptible or very perceptible in both species. No differences were found among the three drying methods in Δ E*, although the season of the year affected dif L* and dif C * significantly.