Excerpt: 'A Splintered History Of Wood' A characteristic that makes wood unique is that even a single piece of wood is variable onto itself.
NPR logo Excerpt: 'A Splintered History Of Wood'

Excerpt: 'A Splintered History Of Wood'

Spike Carlsen's 'A Splintered History of Wood'
A Splintered History of Wood: Belt Sander Races, Blind Woodworkers, and Baseball Bats
By Spike Carlsen
Hardcover, 432 pages
List price: $24.95

The Wood Freak Show

Snow forms in so many guises that the Inuit have 20 names for it; karakartanaq is "crusty snow that breaks under foot," upsik is "wind-beaten snow," and qali is "snow on the boughs of trees." Wood is equally eccentric; it's all over the map when it comes to looks, workability, strength, smell, texture and other qualities.

One characteristic that makes wood uniquely unique, is that even a single piece of wood is variable onto itself. If you take a cubic foot of most things-water, plastic, iron, Jello, Styrofoam or granite-place it in a vise and squeeze, it will react the same way no matter which sides of the cube are between the jaws. These objects are isotropic (they have identical properties in all directions) and homogenous (they're uniform in composition). But not wood; wood is anisotropic and heterogeneous. Depending on which way you placed it in the vise-or drill it, dry it, stretch it, glue it, screw it, plane it, cut it, or almost "anything" it-it will react differently. It even looks different from surface to surface. A cube of oak may be a bulls-eye of concentric circles on one surface, a bevy of lines on another, and a blank slate on yet the third.

If it's not challenging enough to sort out the differences within a single piece of wood, then head to your local lumber dealer or hardwoods store. There you can be amused by an entire freak show of woods; a display that includes the arboreal counterparts to the fat man, Leopard Girl and Tom Thumb.

Weight and density. There are over 100 species of trees and shrubs in the world with wood so heavy that they'll sink. Specific gravity is a ratio used to compare the weight of oven-dried wood to that of an equal volume of water. A cubic foot of water weighs 62-1/2 pounds. If a wood weighs 31-1/4 pounds per cubic foot (as black cherry does) its specific gravity is expressed as 0.5. The heaviest of the heavyweights are certain tropical "ironwoods" (a generic, not scientific name) with a specific gravity of 1.49 and a weight of 93 pounds per cubic foot. The heaviest and densest of these ironwoods are often referred to as "quebracho," which fittingly translates into "axe-breaker." Some of these woods are so dense they've been used for anvils. The wood of the canyon live oak was used for both splitting wedges and the mauls that whacked them by early pioneers. Some of the hardest hardwoods register 2.5 on the mineral hardness scale; copper ranks 3.5. Hardness is closely related to density, which is closely related to weight. If you've got heavy wood, you've got hard wood.

The lightest of the lightweights is the Cuban wood Aeschynomene hispida with a specific gravity of .044 and weight of just under 3 pounds per cubic foot. If you wanted to balance a scale with a cubic foot of ironwood on one side, you'd need to place 30 times as much of the Cuban wood on the opposite platform. Balsa is the lightest commercially used timber; its very meaning in Spanish is "raft." It's used for projects as varied as aircrafts, buoys, insulation and theater props. The tree grows fast, dies young and lives wet. Moisture content is typically in the 300 percent range and there are reported instances of it approaching 800 percent. Trees are ready for harvesting by the age of seven and begin rotting in their early teens unless harvested and dried.

Color. The name Roy G. Biv should ring a bell — at least if you were paying attention to the mnemonic taught in grade school to help memorize the colors of the visible spectrum. Red, orange, yellow, green, blue, indigo, violet. One can come close to creating this rainbow of colors with woods of the natural world.

Red you could glean from the redwood or incense cedar. Orange you could pluck from the Osage orange or yew. Yellow could be whittled from the yellow poplar or yellow buckeye. Green could be shaved from the magnolia. Blue is a rarity in a natural state, though you could harvest plenty of it from lodgepole pines, which have been infected by the mountain pine beetle. (The sapwood, colored by a blue-staining fungus, is even marketed by one company as Denim Wood.) Indigo and violet could be requisitioned from purpleheart. If one wished to add the color that represents all the colors of the spectrum, one would need to add holly for white. And if one wished to represent no color at all, one would select black ebony

It is extractives — the chemicals that work their way into the heartwood belly of the tree as it ages — that produce the richest colors. Different genetic traits and environmental factors produce different extractives, which produce different colors in different woods. Some colorations are quite distinctive and specific; some lumber buyers specializing in African mahogany can reportedly tell which area and port a specific log came from based on differences in color in the heartwood. In some woods the transition from sapwood to heartwood occurs in subtle gradations, but in others it is startlingly abrupt. A cocobolo board I have sitting on my desk has white sapwood that butts up to the deep red-brown heartwood with absolutely zero hemming and hawing in between. And colors aren't stagnant; anyone who's left a hammer on a piece of freshly cut cherry and later returned to find a silhouette of that hammer will attest to that. Purpleheart morphs from purple to brown when exposed to light and air; eastern red cedar can do just the opposite.

Figure. "Figure", in simple terms, is "good grain gone wild." A well-behaved tree in a well-behaved environment will normally produce nice, consistent, growth rings. When that tree is sawn into boards, those growth rings produce grain and figure that's straight, consistent and predictable. Figure — and when most woodworkers use this term, they're referring to pronounced figure — is an aberration in this consistency. For a slab of wood to be branded as figured, three factors come into play: 1) the type of aberration, 2) the way the aberrant section of wood is cut, and 3) whether one perceives it as beautifully figured or something defective to be thrown on the scrap pile

One hallmark of most figured woods is a three dimensionality and translucency. You'll hear terms like "shimmer," "depth," and "luster" bantered about in the hardwoods store. Most of the monikers used to describe figure are quite descriptive. Blistered, ribbon stripe, snail quilt and lace-figure are a few of the less common types of figure; here are a few of the more common.

Birds-eye figure is (surprise) a grain pattern reminiscent of hundreds of small bird's eyes scattered across the face of a board or veneer. It's created when growth rings are distorted as if they'd been poked by a dull pencil. Exactly what this dull pencil is in nature is unknown. Some maintain it's caused by birds pecking on the tree; others by a type of mutant bud which attempts to sprout within the tree, rather than outside of it. Fungi, soil conditions, stunted growth and other causes have been suggested--but none proved.

It's most common in hard maple, but also occurs in birch, ash and, in rare cases, black walnut. Michael Snyder, a forester in Vermont where maple reigns supreme, explains "The birds-eye pattern in wood is much like maple sugaring and fall foliage. We're familiar with it, we value it, and we know a tremendous amount about it. And yet, ultimately, it remains a mystery. For the better part of a century, wood scientists have been beating up on each other's explanations of what causes it. Hell, there isn't even agreement on how to spell it." Snyder has discovered one thing characteristic of most birds-eye-bearing maple trees: A Coke bottle shape to the lower part of the trunk.

Spalted wood is wood that has been infiltrated by "waves" of decay, with each wave leaving a uniquely outlined stain-zone line. The look is not unlike that of the amoeba like figures projected over the stage during a 1960s Grateful Dead light show. Temperature, humidity, type of fungi and chemical reactions all affect the end result. Once the wood is kiln-dried, fungi can no longer grow and the spalting becomes frozen in time. The key is to catch the wood after the magic has begun, but before it gets too punky. Woodturner extraordinaire, Alan Lacer explains, "When wood is captured somewhere between the extremes of being completely sound and fully rotten, it can display magnificent beauty." Again, hard maple seems to be the most frequent beneficiary of this beauty, and lighter woods in general offer the best canvas for Mother Nature to show off her flair for contemporary art.

Lacer offers his recipe for those wishing to create their own spalted wood. Place a freshly cut, 2- to 3- foot long log upright on the bare ground, place a mound of dirt on the top end and cover it loosely with black plastic. Keep it at a temperature of between 60 and 80 degrees F. When the right amount of "spalt" has been attained, lower the humidity level to stop the progress. Since your next step is to cut, turn or route this fungi-laden wood, it's highly recommended you wear a respirator; especially if you have allergies or a weakened immune system.

Burls are the geodes of the woodworking world; baffling in their creation, plain-Jane or outright ugly on the outside, but often magnificent when cut open to reveal the mystery within. They're so convoluted and measurement defying, they're often sold by the pound instead of board foot. Burls are often described as a "cancerous growth"-and this description may not be too far from the truth. Most appear to be some type of genetic flaw that manifests itself in the form of a knoblike outgrowth. They can occur on any tree, anywhere, but are commonly found on elm, walnut, cherry, redwood and (again) our old friend and free-spirited, maple. Based on artifacts, kings and queens of bygone days seem to have been particularly fond of burlwood items. Really, the ugliest thing about burls may be their alleged involvement in introducing Dutch elm disease into the U.S.; the disease may have came over from France in the 1920s when elm-burl was being imported to create veneer for the furniture industry.

Quilted figure, like quilts themselves, comes in many patterns. There's cloud quilt, tube quilt, bubble quilt, muscle quilt and, for those who prefer to visualize in gastronomic terms-popcorn and sausage quilt. Quilted figure is revealed when wood with wavy grain is flat-sawn. The overall effect is a surface with a soft, cumulous cloud-like appearance. Again it is a maple-this time, bigleaf maple-in which this pattern most frequently manifests itself. Blister figure is the miniaturized form of quilted figure and "Quittle" is the nickname bestowed upon wood that has a blend of both quilted and curly figure. When cabinetmakers and wood turners want to create a piece with depth and striking figure, they often reach for their stash of quilted and quittled maple.

Wavy, ribbon and curly grain are byproducts of spiral grain that reverses itself periodically as a tree grows to produce a thing called interlocked grain. Visually these boards have a washboard effect-and as the varied grain intersects the wood surface and light at different angles, a hologram-type depth emerges. Fiddleback is the term often used to describe wavy grain in maple since it's frequently used for you-know-what.

And the list goes on. Bear scratch figure forms when growth rings are indented. Bee's-wing mottled figure is a confluence of several grain patterns. Crotch figure reveals itself when the crotch or branch of a tree is cut lengthwise. There's angel step, cat's paw, peanut shell and flower grain. And it is this rich, rare, one-of-a-kind figure that is the golden grail from which woodworkers can create works of unspeakable beauty-and for which hardwood dealers can charge unspeakable prices.

As much as we love figured wood, we really know very little about how it's formed. Scientific study is lacking; trees do not fit in test tubes and rare is the scientist who has the patience, foresight and funding to conduct a 30 year long experiment, with little chance of monitoring progress along the way, and no way of determining results without a chainsaw. But it seems there's little we can do to create it or even encourage figure. It doesn't seem to be affected all that much by climate, soil conditions, geographical location, growth rate, tree size or disease. We do know about figure formation in one specific tree: When strangler figs wrap their vines tightly around young mahogany trees, the resultant struggle gives birth to drape figure.

There have been a few successful attempts at growing or stimulating figure. A blistered or crinkle figure can be "manufactured" in Japanese cedar by propagating cuttings taken from older trees with crinkle figure. There's been success in creating figure in the same tree by binding bamboo sticks tightly around the trunk with elastic cord to create "dents" in the growth rings. There's been limited success creating burls in boxwood by putting close-fitting metal bands around stems. Burls can also be coaxed into African thuja by repeatedly burning certain areas of the trunk and branches. In 1929 J. F. Wilkinson grafted cuttings from a figured walnut tree and saw evidence in the offspring 22 years later. But for the most part, figure remains a mystery. It may simply be that each tree, like each person, is an individual, and has a personality that's a product of both nature and nurture.

Odor. Wood knocks on all of our senses, including smell. Blindfolded nearly everyone can detect incense cedar; average woodworkers can often sniff out sassafras, red cedar and Douglas fir, and avid woodworkers with a keen nose can detect the subtle aroma of catalpa, teak and other woods they commonly work.

Cedar is perhaps the most commonly harnessed wood fragrance today. You can find it in board form as cedar closet lining, in stick form as incense, in flake form as sachet, and in liquid form as a room freshener and massage oil. The pungent odor of aromatic cedar is generated as oils evaporate from the heartwood. The debate rages as to whether the wood truly acts as a moth deterrent. There's evidence that the wood will kill small moth larvae, but there's more evidence that once the oils evaporate, the wood loses its repellant qualities. A light sanding can renew the smell, but it seems that at least part of the effectiveness of cedar lined closets and chests is that they're often built very tightly to keep in the smell--which in turn keeps out the moths.

A few exotic woods have exotic smells. Coachwood has the nose of newly-cut hay, while camphorwood smells, not so surprisingly, like camphor. Sandalwood has a spicy odor; those harvesting it will often chop it down, let it lay for several months so ants can eat the inodorous sapwood, then process the odiferous heartwood into various products. Not all is sweet smelling in the world of wood. When the question "What's the worst smelling wood you've ever worked?" was posted on one woodworking website, the opinions were as strong as the odors of the woods discussed. Many thought first place should go to acacia with comments like "It smelled like every animal in the neighborhood had taken a dump in my workshop." Other votes went to hoop pine that "Smelt like the worst pair of rotten socks I had ever smelt" and silky oak which "smells like gone cheese." Several trees, including laurel and ocotea bullata, have earned the nickname "stinkwood." Dahoma wood smells like ammonia. Yellow stercula appropriately derives its name from the Greek word "manure." The agreeableness of satinwood's odor depends somewhat on your ornithological fervor. Albert Constantine explains, "A peculiarity of the wood is that while it burns in an open fireplace very well and with a fragrant restful odor, inducing slumber in many who sit before it, the smoke of this satinwood will kill canaries."

Wood can hurt more than canaries. Wood: Identification and Use lists no fewer than 170 woods deemed toxic. Hang around too much cocobolo dust and you might find yourself with conjunctivitis, bronchial asthma and nausea. Teak dust can cause swelling of the scrotum and over-sensitivity to light. American mahogany, black cherry and iroko sawdust can cause giddiness. Dust from the jacareuba tree can cause loss of appetite, and dust from the milky mangrove can cause temporary blindness. White cypress sawdust can lead to nasal cancer and swelling of the eyelids. There's even evidence linking the wood dust from commonplace oak and beech to cancer of the upper respiratory tract. If you're allergic to aspirin, avoid contact with willow and birch; they could cause similar adverse reactions. And, while you're at it, try to avoid splinters from mulga wood found in Australia; the wood contains a poison aboriginals use on spearheads.

It is all of these different factors-species, density, color, odor, figure-that creates the tremendous diversity in wood. Like the snow and snowflakes with which this chapter began, each and every piece of wood is unique.

Excerpted from A Splintered History of Wood: Belt Sander Races, Blind Woodworkers, and Baseball Bats by Spike Carlsen. Copyright © 2008 by Spike Carlsen. Excerpted by permission of HarperCollins Publishers, Inc. All rights reserved.

Books Featured In This Story