Spalted wood has gained popularity in recent years as consumer preference has shifted towards unique and custom products. The process by which spalting is induced in clear lumber has evolved over time, and now involves much more than beer drinking and outdoor burial. Our work on the process of reliably producing spalted wood began in 2004 and involved testing a wide variety of white rot fungi on sugar maple for their bleaching and zone line producing ability. Results from this study indicated that Polyporus brumalis and Trametes versicolor reached maximum spalting capacity at 10 weeks before machinability ratings dropped below the acceptable threshold, and Bjerkandera adusta and Trametes versicolor reached the same capacity at 8 weeks (Robinson et al. 2007a, 2007b). In subsequent work, sugar maple blocks were pressure treated with sub-lethal levels of copper sulphate in an attempt to stimulate spalting, and inoculated with one of several known spalting fungi. Results were highly variable and differed with changes in medium (incubation in soil versus vermiculite). Blocks incubated in soil had higher weight loss than those in vermiculite. Blocks incubated in vermiculite had higher amounts of copper stimulated spalting than those in soil. Preliminary results indicate that very low levels of copper sulphate do stimulate spalting, and that vermiculite is a preferred spalting medium due to low weight loss and spalting stimulation in the presence of copper sulphate.

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