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.
Highlights
There is a long history of use of natural and synthetic colorants on wood products to enhance visual appeal, with the documentation of Pliny the Elder (23-79AD) as one of the earliest accounts of such wood modification [1]
In terms of visual color change, all treatments covered all surfaces of the test blocks, with the green colorant from Chlorociboria aeruginosa (Figure 1) being striking
No visual external coloration occurred from liquid cultures of C. aeruginosa, significant delta E* values did occur on red alder and Oregon maple, indicating that color change took place, but it was not sufficient to effect a visual color change
Summary
There is a long history of use of natural and synthetic colorants on wood products to enhance visual appeal, with the documentation of Pliny the Elder (23-79AD) as one of the earliest accounts of such wood modification [1]. Laboratory research has managed to decrease the maximum incubation time necessary for inducing spalting to around twelve weeks [3] This amount of time is still too long to appeal to many woodworkers used to the instant effects produced by aniline dyes. A new method has recently been developed to extract the colorants produced by some of the popular spalting fungi to produce a solution similar to that of an alcohol-solubilized aniline dye [4] How this colorant solution moves through wood, the concentrations necessary to develop the same intensity of color as given by aniline dye, and the best method to achieve internal coloration have yet to be explored. If similar results can be achieved, woodworkers will have a comparable method for coloring wood that does not utilize synthetic colorants, and that maintains the use of an historic art form
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