Influence of initial wood quality and drying process on utilization grades of sawn spruce timber

Abstract

European spruce (Picea abies Karst.) belongs to the most easily dried wood species, but nevertheless cracking and warping often reduce the quality of dried sawnwood. Larger surface and end cracking was noticed at industrial drying practice in cold winter season, especially in using fast drying schedules. For the assessment of factors influencing the quality of dried wood some drying runs with varying drying conditions were carried out in an experimental kiln dryer. The quality of sawnwood was evaluated on green material using standard procedures and compared with the quality at the end of drying processes. Drying of spruce sawnwood at sharper drying conditions was more risky, resulting in a larger number of cracks as well as larger final MC distribution, larger MC gradients and casehardening. Additionally, significant correlation was confirmed between the quality of dried wood and input quality of fresh material. More downgrading after the drying was observed in case of initially low graded material.