Drawing the zone line: Fungal melanin and novel methodologies in spalting

Spalted wood, or wood with discoloration from wood‐decay fungi, has a centuries‐old history of use as a material in artistic woodworking. Unfortunately, spalted wood is often structurally compromised and can require knowledge of advanced woodworking techniques to use. In recent years, efforts to extract pigmentation‐type spalting metabolites from wood and fungal culture have allowed for the use of spalting extracts to be used as colourants on sound wood. Due to the uniquely challenging chemistry of melanin, which forms the basis for zone line type spalting, these black and brown pigments are not currently utilised despite being popular worldwide. In an effort to add fungal melanin and zone lines to the extracted spalting palette, this work tested ideal combinations of fungal species and culture medium to maximise melanin production and then developed an extraction methodology. Although most of the tested fungus and media combinations produced melanin in static culture, of the 12 fungus‐medium combinations tested, Xylaria polymorpha grown on yeast–peptone–glucose (YPG) medium produced the highest quantity of extractable melanin suitable for reapplication (203.4 mg per plate) despite having a visually lower amount in culture. While future research will need to develop methods to transform the extracted melanin into an ink or other colourant, the creation of extracted zone line pigments should enable the growth of the extracted spalting market, facilitate the creation of non‐decayed spalted works, and expand the understanding and use of spalted wood products across woodworking communities in the United States as well as internationally.