Prediction and evaluation of borate distribution in Eastern black spruce (Picea mariana var. mariana) wood products

Borate distribution and content in re-wetted brush-treated Eastern black spruce (Picea mariana var. mariana) blocks were investigated by near-infrared spectroscopy (NIRS). Samples were brush-treated with 40 % glycerol-based DOT (Na₂B₈O₁₃ 4H₂O) and then conditioned for different durations (5, 9, 20, and 30 days) at high relative humidity (approaching 100 %). The effect of a glue-line on the borate distribution and content was also evaluated. Borate penetration depth was estimated in the radial direction in wood block samples. The evaluation of borate’s diffusion gradient in terms of boric acid equivalent was conducted on the whole radial plane of the other portion of wood samples that were sliced every 0.4 cm in the radial direction. The effect of glue-lines was evaluated using two wood strips glued together. Calibration models achieved R ² ranging from 0.4 to 0.5 and root-mean-square error (RMSE) ranging from 0.28 to 0.31 %. The statistic for validation achieved R ² ranging from 0.3 to 0.4 and RMSE ranging from 0.31 to 0.34 %. NIRS had some predictive abilities for borate distribution and borate concentration using the projection to latent structures-PLS regression method.