Wood Colorization through Pressure Treating: The Potential of Extracted Colorants from Spalting Fungi as a Replacement for Woodworkers’ Aniline Dyes

Abstract

The extracellular colorants produced by Chlorociboria aeruginosa, Scytalidium cuboideum, and Scytalidium ganodermophthorum, three commonly utilized spalting fungi, were tested against a standard woodworker’s aniline dye to determine if the fungal colorants could be utilized in an effort to find a naturally occurring replacement for the synthetic dye. Fungal colorants were delivered in two methods within a pressure treater—the first through solubilization of extracted colorants in dichloromethane, and the second via liquid culture consisting of water, malt, and the actively growing fungus. Visual external evaluation of the wood test blocks showed complete surface coloration of all wood species with all colorants, with the exception of the green colorant (xylindein) from C. aeruginosa in liquid culture, which did not produce a visible surface color change. The highest changes in external color came from noble fir, lodgepole pine, port orford cedar and sugar maple with aniline dye, cottonwood with the yellow colorant in liquid culture, lodgepole pine with the red colorant in liquid culture, red alder and Oregon maple with the green colorant in dichloromethane, and sugar maple and port orford cedar with the yellow colorant in dichloromethane. The aniline dye was superior to the fungal colorants in terms of internal coloration, although none of the tested compounds were able to completely visually color the inside of the test blocks.

Feasibility of Coloring Bamboo with the Application of Natural and Extracted Fungal Pigments

“…This can affect the visibility of the pigments, where areas with a higher concentration of vascular bundles will have a more visible concentration of pigments, compared to areas with fewer bundles. This is correlated with the findings by Robinson et al [20], where the authors found that the dispersion of the fungal pigments into small dots (or zones) did not create a visibly detectible color change.…”

“…A similar effect was observed in a previous study by Robinson et al [18,20] on wood, where the authors postulated that there might be a significant internal color change; however, this color change is not visible to the naked eye. For a significant color change to be perceivable to the human eye, the value of the ∆E must be higher than one [20]. Because of the lack of a perceivable color change, the fungal pigments might not be suitable for their use for internal pigmentation on bamboo.…”

Utilizing Extracted Fungal Pigments for Wood Spalting: A Comparison of Induced Fungal Pigmentation to Fungal Dyeing

“…Dichloromethane was found to be the most effective solvent. Pressure treating of wood samples with this extracted pigment proved to be very successful for surface pigmentation but did not significantly produce any visible colors internally [15]. However the application was very fast, taking an hour to fully color the outside of the test samples.…”

Determining the Presence of Spalted Wood in Spanish Marquetry Woodworks of the 1500s through the 1800s

“…As Chlorociboria fungi first seek out free sugars in wood, then later begin to degrade the wood cell wall [17], colonization, and thereby color, is uneven in wood, as wood sugar placement within wood is uneven [1,16]. In contrast, dyed wood typically has color primarily in the vessels and fibers (the path of least resistance), but seldom in the ray parenchyma (smaller, horizontal cells are more difficult to flow into) [10]. Additionally, the color dispersion in dyed wood tends to be much more even across affected cells, due to how the dye is placed into the wood (submersion, vacuum, etc.…”

“…Kanouse, Chlorociboria aeruginosa (Oeder) Seaver, Scytalidium cuboideum (Sacc. and Ellis) Sigler and Kang, and Scytalidium ganodermophthorum Kang, Sigler, Lee and Yun [5][6][7][8][9][10][11][12][13][14][15]. Of these four species, the Chlorociboria species and the blue-green pigment they produce, known as xylindein, have the most historical significance in terms of historical woodwork.…”