Transformative Technologies Program ; Project No. TT5.15
Wood color has an important economical impact on wood products. The hardwood lumber industry is facing a particular increase in demand by their customers for wood with an attractive, consistent and specified color. Fungi are a specific group of micro-organisms that can affect wood color. Some fungal species produce various colorful pigments during their growth and can create a preferable color or pattern on wood products, whereas some other species produce bleaching enzymes that can clean unpleasant stained wood products. The objectives of this project were to increase the average value of the hardwood lumber product mix by developing a biological technology to eliminate undesirable wood colors and to produce attractive and consistent wood colors and patterns.
Thirty-five fungal species were selected for coloring wood of sugar maple, white birch and yellow birch, whereas 20 fungal species were selected for decolorizing stained wood (chemical or biological stains) of sugar maple, yellow birch and white pine. The wood samples were dip-treated for 30 seconds in spore suspensions and incubated at 25°C and 75% RH up to 8 weeks. Wood color changes were visually inspected weekly and final colors were measured with a colorimeter.
The results of coloring wood show that 15 fungal species are promising to color wood of sugar maple, white birch and yellow birch into red, brown, green, grey, black and purple. The heartwood was equally colored as sapwood with most fungal species. Application of 3 or more selected fungal species together on a piece of wood was able to produce a rainbow wood pattern with multiple colors. The process for coloring wood required 1-4 weeks. Weathering gradually reduced color intensity of biologically stained wood if without a protective coat.
The results of decolorizing wood show that 17 fungal species are promising: 10 fungal species were able to decolorize white pine blue stain, 3 species decolorize white pine coffee stain, 10 species decolorize sugar maple stains and 11 species decolorize yellow birch stains. Based on visual and instrumental evaluation for color brightness and uniformity of decolorized wood samples, 3 fungal species were identified as potential candidates for decolorizing white pine blue stain, 1 species for white pine coffee stain, 4 species for sugar maple stains and 4 species for yellow birch stains. The process for decolorizing wood required 2-8 weeks.