Spalting Process Spalted Oak Vase with spalting patterns. As a tree decays Spalting occurs. It produces black line patterns from mineral deposits and fungi as they enter the log. As the process continues the wood becomes punky and falls apart. There is a short period of time when the spalting is useful before the wood becomes unusable. The woodworker has a narrow window to mill the log into usable lumber. Once the log is processed into lumber the spalting process stops.