A reprint from American Scientist the magazine of Sigma Xi, The Scientific Research Society

This reprint is provided for personal and noncommercial use. For any other use, please send a request to Permissions, American Scientist, P.O. Box 13975, Research Triangle Park, NC, 27709, U.S.A., or by electronic mail to [email protected]. ©Sigma Xi, The Scientific Research Society and other rightsholders The Fine Art of Decay

A woodworker becomes a scientist in seeking out the perfect fungal pigments.

Sara C. Robinson

he sheer magnitude of decay bowls brought in by my woodshop art degree if it meant having access to in the of the Pacific teacher to bother with math, physics, or multiple lathes. I’m easily persuaded Northwest, where I live, is chemistry. Academics weren’t for me. by shiny pieces of metal. thrilling and sometimes over- I wanted to turn, and I wanted to do it Four years later I was blocked, left Twhelming. Life in these forests involves with brightly colored . with a solid grounding in art but no soggy leaves, soggy children, and that My parents were hoping I would real additional wood skills. There was ever-present smell of decomposing choose a four-year degree, any four- no one to supply me with brightly vegetative matter. Children love colored wood, either, and most to crawl around on the forest of my turnings from this time floor for treasures. And who relied on playing with the in- hasn’t enjoyed kicking apart a terface between the dark inner soundly rotten log, watching heartwood and the lighter outer the dry bits scatter, and hear- sapwood to keep my aesthetic ing the mushy bits make that attention. I was bored; I was up- delightful squelching sound? set. I wanted more information I’m certainly not one to deny about wood so that I could be such visceral pleasures of the a better woodworker, not more forest. But that log is so much history lessons. more than decay. It is an eco- Michigan Tech’s forestry pro- system, a potential nurse log gram ended up offering me the for new , or cover for small opportunity to learn more, but animals. Insects, bacteria, and in a rather convoluted fashion. fungi work together to provide I applied to a master’s degree a steady stream of nutrients program there through the Peace that are cycled again and again Corps, hoping that two years through the forest. It is also abroad might help quell my something much more personal: growing wanderlust. But when It is art. And it is my life. two successive placements fell I wasn’t always obsessed with through due to bad timing and . As a teenager, I knew local rebellions, I was left with only that I wanted to be a wood- no option other than a standard worker, and I spent countless master of science degree. hours in my high school wood- In desperation, I contacted shop learning furniture design the only professor of wood sci- and turning. I couldn’t have ence left at MTU, Peter Laks, cared less about other subjects; by the Pigments and zone lines caused by spalting and asked him if he knew of any type time my senior year rolled around I was in sugar wood (Acer saccharum) show- of project that I could work on to fin- too busy turning red-stained boxelder case a stunning variety of colors. ish my degree. We chatted. I’m sure he thought I was nuts. Eventually he year degree, over a carpenter appren- asked me to bring in examples of some Sara C. Robinson is an Assistant Professor in ticeship. Through a great deal of re- work that I had really enjoyed. I pulled the anatomy of renewable materials at Oregon search on their part (I had nothing to a bright red bowl from my days in high State University in the Department of Wood do with it—I had no interest in col- school and brought it to him, gushing Science and Engineering. She is also an artist and displays her work in juried shows through- lege), they found a university that about wood colors. Boxelder wood is out the world. You can peruse her work at www. offered a four-year degree in wood- typically a pale cream color, but occa- northernspalting.com. Address: 119 Richardson working. After one trip to visit, upon sionally streaked with bright red/pink Hall, Oregon State University, Corvallis, OR seeing the room filled with lathes, I stain, usually around areas of knots or 97331. Email: [email protected] was hooked. I agreed to pursue an other wounding. This bowl showcased

206 American Scientist, Volume 102 © 2014 Sigma Xi, The Scientific Research Society. Reproduction with permission only. Contact [email protected]. A love for lathes for wood-turning and working with brightly colored wood led to a career in science studying fungal pigments. Work in the lab resulted in colorful spalted bowls, such as this one. (All photographs courtesy of the author, unless otherwise noted.) the reason the popular term for stained it became apparent that fungi could in scientific community was particular- boxelder wood is flame stain. The con- fact cause colors on wood (although ly interested in inducing them. They versation went something like this: fungi did not cause the flame stain in were associated with decay, and wood boxelder that launched my research), scientists had spent decades trying to Dr. Laks: “Interesting bowl. What I started experimenting with fungi. keep fungi off wood to prevent struc- makes the colors?” Which ones made the appealing col- tural damage. Wood crafters and art- ors? Which ones made those neat ists weren’t too interested in fungi ei- Me: “I don’t know. Beetles? I lines? I was mesmerized by the idea ther, seeing them as either pests that think? Maybe fungus?” of living art, using pigments produced discolored wet wood or deadly hu- Dr. Laks: “Are there other colors through natural growth processes to man pathogens that should never be like this?” color wood. And, to be honest, I was brought into the house. Amusingly, mostly excited about making neon- spalted wood has actually been used Me: “Uh, maybe?” colored bowls. in craft since at least the 1500s, if not Thus my entire future was launched. Through my research I found that before, and entrepreneurs have been I pulled papers and did research. I although a lot of the pigment residues attempting to stimulate wood pig- began to delve into a history of an- left by fungi on wood, called spalting, mentation for economic gain since the cient craft and modern science. Once were known to science, no one in the very early 1900s. But no one had really www.americanscientist.org © 2014 Sigma Xi, The Scientific Research Society. Reproduction 2014 May–June 207 with permission only. Contact [email protected]. been able to reproduce spalted wood but unable to cause substantial decay, winding, sometimes thick, sometimes reliably, and especially not in any type grow slowly inside the log, some be- thin line of black, brown, yellow, or- of quick time frame. fore the rots, some concurrently, some ange, green, or red, is composed of The trick to controlling wood spalt- after, digesting the easy sugars of the pigments, primarily melanin. Zone ing, it seemed, was a thorough un- wood rays and occasionally produc- lines are thought to serve a variety of derstanding of the biological process. ing melanin and other pigments in an functions depending on the fungus. Wood decay fungi in the phylum Ba- attempt to protect their resources from Some may help prevent desiccation sidiomycota, which includes all mush- desiccation, light, or other fungi. of the log; others may protect against rooms, come in two primary groups: Fungi do not always play nicely with damage from ultraviolet light. What the brown rots, which predominate each other. There are limited resources is well proven is that many white rot on , and the white rots, which in any given log, and many fungi want fungi will erect zone lines if they de- prefer hardwoods. White and brown a piece of the action. Those that can col- tect the presence of another fungus of rots generally only grow in dead or onize quickly have an initial advantage, comparable strength. And although severely stressed trees. Unlike the rest but, as in any war, you have to be able most zone lines occur at the bound- of mycology, in which technical jar- to hold the land you’ve captured (not ary between two different white rot gon dominates, the terms white rot and just plant your flag and go) if you want fungi, they have also been documented brown rot are actually very descriptive lasting success. The beautiful colors and surrounding soft rot fungi and various of the end result of the log. Brown rot boundary shapes produced by some pigmenting fungi from the phylum As- fungi leave behind a crumbly, brown, of these wood-colonizing fungi are a comycota, which produce sac-shaped lignin-rich shell. White rot fungi, ca- by-product of the means by which to fruiting bodies rather than the stereo- pable of breaking down lignin, leave protect their property. typical mushroom shape. behind mushy, lightened wood in- One major artifact left behind by But pigmentation doesn’t happen stead. Other fungi, habituated to wood white rot fungi is a zone line: This just in zone lines. Some fungi, most no-

White rot (left), and zone lines resulting from white rot antagonism, among other mechanisms (below). At bottom, a microscopic view of a zone line show melanin formation in the lumens of sugar maple wood. Photograph at bottom courtesy of Daniela Tudor. Dr. Jeremy Burgess/Science Source

208 American Scientist, Volume 102 © 2014 Sigma Xi, The Scientific Research Society. Reproduction with permission only. Contact [email protected]. tably the Chlorociboria genus, produce The Art History of Spalting way to avoid harsh dyes and sought it extracellular pigment that changes the As I discovered several years later, out for use in their works. color of the wood where they grow. It however, pigmented wood was not Unfortunately, the Industrial Rev- is thought that pigment secretion is a unknown to the art world. There are olution, when handmade craft gave way to quickly capture a log so that a plethora of examples of the green- way to machine-manufactured prod- other fungi cannot colonize it, giving stained Chlorociboria-infected wood ucts, played a large role in the de- the slow-growing Chlorociboria spe- in European (wood inlay that creasing interest in intarsia and nat- cies time to establish. Other pigment uses tiny pieces of wood to make a urally pigmented wood, and by the fungi—such as the Ophiostomatoids, larger picture). The blue-green wood early 1900s, the use of spalted wood which produce a dark melanin that of Chlorociboria was commonly uti- in wood crafts was down to a trickle. appears blue due to light refraction lized as color for grass or water, and Even the arts and crafts movement, off the wood, and the multicolored ge- was a prized find by many crafters. designed to raise awareness of hand- nus of Scytalidium—may have a va- An easily accessible example is the made craft, keep old techniques alive, riety of other reasons for producing pulpit intarsia in St. Mary’s Church and value the craft over machine- pigments, such as a reaction to compo- in Greifswald, Germany, by Joachim based products, didn’t keep this col- nents within the wood or environment Mekelenborg. In addition to blue- ored wood in use. or a response to environmental stress. stained wood (common in sky areas), But like any beautiful thing, colored But the effect is the same: Out there, in wood marked with zone lines was wood couldn’t stay hidden for long. the forest, is a crayon box filled with also used in intarsia. There wasn’t a In the 1970s Mel and Mark Lindquist, pigmenting fungi that are drawing all technical name for such wood (“Pilz-­ a father–son duo, were making waves over downed and decaying wood in Pigmente,” as it was called in Ger- in the craft and art scene with their use an attempt to carve out an existence in man, literally just means fungus pig- of found zone-lined wood for wood a competitive world. ment), but artisans saw its value as a turnings. They gained a great deal of

The fungi in the genus Chlorociboria have bright blue-green fruiting bodies (right) and cause blue-green pigmenta- tion throughout the wood in which they grow (far right). Wood with a green stain caused by this fungus was used as inlay depicting a bird and leaves in the pulpit intarsia in St. Mary’s Church in Greif- swald, Germany (above). (Photograph above courtesy of Hans Michaelsen.)

www.americanscientist.org © 2014 Sigma Xi, The Scientific Research Society. Reproduction 2014 May–June 209 with permission only. Contact [email protected]. Growing Pigmented Fungi in the Lab Growing pure culture media in the lab is key to controlling spalting. Understanding growing conditions, type of media, and the general personality of different species can shave months off of incubation time. Scytalidium cuboideum sporulates heav- ily in culture and releases a pink, red, or orange pigment into the media (left). Left for too long, however, this species will start to produce melanin, which will show as a blue pigment. This is a reac- tion to the pH change in the media and can be a real pain when spalting if you just want the pink color.

After five colonies of a fungal species in the genus Chlorociboria have grown on malt agar plates for one month, one can already see blue-green pigmentation.

Scytalidium ganodermophtorum grows Six months after inoculation, this Chlo- When sterilized wood chips of white- more slowly than Scytalidium cuboide- rociboria species is at full-diameter rotted sugar maple (Acer saccharum) are um and is a heavy sporulator. It releases growth. This fungus grows so slowly added to the malt agar, five colonies of a yellow, brown, or green pigment into in media that it is rare to have a single the same fungus grow much faster: The the media, beginning at a light canary plate completely filled with the blue- image above shows the growth after yellow and deepening to brown, until green pigment. Adding sterilized chips five days. finally reaching a grass green over time. of prespalted wood, however, stimulates the growth of this fungus, so that full pigmentation is achieved at 10 days.

media attention after they authored was hailed as the new design trend in encompassed a much wider definition several articles about spalted wood in woodturning. than simply black lines—even zone Fine , the premier wood Due to the emphasis on zone lines lines could occur in different colors. magazine of that time. These two gen- by spalted wood users, my own wood So when I began publishing my re- tlemen turned the word spalting into research in the mid-2000s began heav- sults on how to induce spalting under a name to describe zone-lined wood ily focused within this area. But I controlled conditions and began nam- (its definition was later broadened by also experimented with blue stains, ing fungi that could reliably produce my own research). Although this re- because the fungi that produce such spalting, even though I was primarily emergence of spalted wood as a craft color are numerous. Initial experi- working with zone lines at the time, I and art tool brought naturally colored ments attempting to induce zone lines reset the definition: Spalting was any wood back into the forefront of pub- in clear lumber led to more research color on wood caused by a fungus. lic consciousness, the pigments were and more reading, and it became Woodturners, the group most in- left forgotten, and zone-lined wood quickly apparent to me that spalting terested in spalted wood, were rav-

210 American Scientist, Volume 102 © 2014 Sigma Xi, The Scientific Research Society. Reproduction with permission only. Contact [email protected]. Spalting Wood in the Lab The pigment fungi are the key to mak- ing a two-year process in the field take two hours in the lab. Using either nat- urally pigmented wood from the for- est floor or, in our case, the pigmented wood agar plates, you can submerge the colored wood in any number of organic solvents (below). The resulting solution can then be reapplied directly to spalted or unspalted wood and if put on slowly, does not run over the surface (right). Many of the useful solvents, like ace- tone, run quickly through the wood and carry the pigment through as well, giv- ing surface-to-surface color in seconds— instant spalting! As a bonus, the solvent can be evaporated off, and the pigment can be stored dry, making “spalting on the go” possible as well (below, right).

enous for information about how to patience, and variable mixtures of wood only requires a log and two irri- improve and expand their craft. It was leaves, wood chips, and beer (and var- table white rot fungi. I wanted color. I broadly understood that fungi were ious other amusing spalting recipes). turned my focus back to the pigments, at least partially responsible for spalt- Lab-derived directions for speeding notably the greens and pinks. ing, but which fungi and how best to up growth and getting a reliable result This turned out to be a trickier en- get said fungi in the wood was still were finally available. Interest grew, deavor. In nature, the brighter pig- a mystery. Conjecture had ruled the along with commercial demand. So ments, whether in zone-line or full- gossip chain and Internet for so long my research kept going. Eventually I coverage form, are hard to locate. True that once artisans had actual fungi to became bored with zone line research, wood-inhabiting fungi will be inside experiment with, the topic exploded. because wood with black zone lines is the log, not growing on the surface With the release of my research, at- exceptionally easy to find in the for- (Penicilliums and Trichodermas, com- tempts to induce spalting in work- est. It is also easy to induce in a lab or mon airborne molds that only discolor shops was no longer a practice in luck, garage, because the production of such the surface of wood, need not apply). www.americanscientist.org © 2014 Sigma Xi, The Scientific Research Society. Reproduction 2014 May–June 211 with permission only. Contact [email protected]. Clockwise from above left: Wood specimens found in an Amazon rainforest in Peru showcase orange zone lines, black zone lines with yellow pigment, green and purple stain, and black zone lines with pink pigment.

If you want pigmented wood, you’re plates. I found that Chlorociboria spe- our target fungi to rapidly secrete going to have to dig for it. These fungi cies are especially tricky, because iso- pigment. What once took months for also tend to be slower growers without lates can take months to grow to ad- substandard results now took 10 days any real decay ability (with one species equate sizes and do not perform well with amazing results. called Scytalidium cuboideum being a under wood inoculation conditions. We ended up with hundreds of glaring exception). They are usually While doing postdoctoral research at sheets of wood fiber in the lab, pig- found on logs that are already well the University of Toronto, my research mented with green, blue, red, pink, or- colonized by basidiomycete fungi like took off in this direction: how to en- ange, and yellow. We were awash in a white or brown rots. This means that courage pigment fungi to grow and rainbow of colors we never expected to the wood is soft, punky, and generally produce their colors under controlled have in any sufficient amount. Sudden- unusable unless you want to do histor- conditions. They obviously weren’t ly, the possibilities for these fungi were ic intarsia, or to sink about $20 worth going to be motivated by money or massively expanded. The pigment of plastic stabilizer into the wood. a new car, so we had to get creative. was extractable and easy to re­apply It also means that color-producing It turned out that a simple addition to wood where we wanted it—no fun- fungi can be difficult to grow in a lab, of white-rotted wood, finely chipped, gus growth needed. The pigment also where the majority of my work was sterilized, and added to our standard had an affinity for textiles, and our lab taking place in plastic tubs and Petri malt agar media, was enough to get exploded with samples of every fiber

212 American Scientist, Volume 102 © 2014 Sigma Xi, The Scientific Research Society. Reproduction with permission only. Contact [email protected]. Fungal pigmentation in wood opens up the possibilities for a plethora of designs and colors, which Robinson showcases in her wood-turned bowls. Clockwise from top left: Curly red maple with zone lines and green stain of Chlorociboria fungi via extracted dye; sugar maple with zone lines with blue, orange, purple, and pink stains from a menagerie of inoculated fungi; curly red maple with zone lines and pink, orange, yellow, and grain stains applied with extracted dye; with zone lines resulting from inoculation with the white rot fungus Xylaria polymorpha. imaginable, all brightly hued and cov- of both science and art. Our biggest pigments are used, whether for beauti- ering every available surface. struggle is deciding on which paths ful, time-consuming , prefab With this breakthrough, modern to follow first. Questions that cur- wood veneer floor, or your next pair of spalting was born. A mixture of biol- rently interest us include: Do the pig- running shoes. No matter where our ogy, artistry, and luck, the process de- ments have any UV stability? Do they research takes us next, it is guaran- veloped for the lab has reduced incu- have any medical potential? Can they teed that it will be brightly colored and bation time from one to two years in be used as dyes for acrylic paints or beautiful. the wild to about two hours in the lab, dyes for clothing? Does spalting mean still using the same fungi. wood colored with fungi that are actu- Today, my lab in the Wood Science ally grown on the wood, or can it still and Engineering Department at Or- be spalting if the fungi are grown on a egon State University is filled with different piece of wood, then the colors For relevant Web links, consult this excited graduate students and un- transferred in a directed manner? ­issue of American Scientist Online: dergraduates, all who have different We are all very excited about the http://www.americanscientist.org/ ideas about how these pigments can evolution of this ancient art. But in the issues/id.108/past.aspx be used. Nothing is off-limits—we’ve end, the consumer and artist will dic- become a lab of random experiments, tate how spalted wood and extracted www.americanscientist.org © 2014 Sigma Xi, The Scientific Research Society. Reproduction 2014 May–June 213 with permission only. Contact [email protected].