Wet storage of birch logs for protection against discolouration

Discolouration (“bränning” in Swedish) is a well-known problem that can occur if birch logs (Betula sp.) are stored outdoors for more than a few weeks during the summer. The risk of discolouration, combined with the considerable need for storage during the summer owing to the uneven wood supply and the closing of mills for vacation, represents a substantial problem for Swedish sawmills specialising in birch. Traditionally, wet storage (i.e., irrigation or sprinkling) has not been used in Sweden to protect birch logs. The documented knowledge of the wet storage of birch is very limited compared with the detailed knowledge of softwood wet storage. Therefore, a storage study was performed in southern Sweden to compare the end-surface discolouration of wet- and dry-stored birch during 12 weeks of summer storage. Two full-sized experimental piles of roundwood were set up at a log yard. One of the piles was properly water sprinkled during the entire period, whereas the other pile was dry stored. The logs from the piles were compared to determine the potential of wet storage for protecting stored birch. The results showed that wet storage significantly reduced discolouration in comparison with the discolouration observed in dry-stored logs