Often tossed aside as damaged wood, craftsmen are seeking out spalted wood more and more for exactly the reason it is often trashed. Spalted wood creates some very interesting and unique patterns that show up beautifully when used in turned bowls, pens or furniture. Darker strands travel haphazardly throughout a piece of spalted wood, creating contrasting waves and lines that enhance the grain as only nature can. But what is spalted wood?
Photo courtesy of Woodcraft Magazine
What is spalting?
Spalting is actually a fungus growing in the wood – this is what creates the black lines you see. If the fungi grow too long, the wood will deteriorate. The trick is to find it when it isn’t quite to the “rotten,” soft stage, to preserve the beauty of the interesting patterns created. Much of the spalted wood found on the market today is created rather than harvested. Woods such as tamarind, maple and elm are cut and then have their moisture contents carefully controlled to create the spalting, without too much weakening of the surrounding wood.
Stabilizing the wood stops the deterioration process, enhances grain appearances, increases water resistance, and hardens the wood, making it more durable for turning, sanding and polishing. It becomes much less likely to crack or move when stabilized. This is done by placing the wood under pressure in a pot that forces polymers/acrylics into the wood or by drying the wood in a kiln. Sometimes dyes are added for color, as shown.
In the interest of saving time, buy wood that is already stabilized. But if you have the time and desire, you can do it yourself by first allowing the wood to sit for a month or so to remove the moisture, then injecting hardeners into the soft areas to prevent further decay.
Spalted Tamarind (Tamarindus indica)
Spalted Tamarind is one variety of spalted wood that Woodcraft carries. It has spectacular heartwood with background colors of ivory, yellow and black lines, which gives an unpredictable landscape effect. Much of the wood comes from logs that were found on the forest floor.
Tamarind trees, native to tropical Africa, are widely known for their fruit. Though the hard green pulp of its young fruit is a bit too sour for most tastes, it is commonly used in recipes, as a pickling agent or to make certain poisonous yams safe to eat. The ripened fruit becomes sweeter as it matures and is used in desserts, blended into snacks like sorbet and ice cream. In Western cuisine, it is found in Worcestershire sauce.
It is important to note that tamarind and other acrylic impregnated woods perform more like plastic than wood. “Dyed” and “acrylic impregnated” woods may look similar, but they are very different. What you trade off in mold tendencies, you gain in stink factor from the acrylic when working it.
Working with Spalted Wood
Certain considerations should be kept in mind when working with spalted wood.
SELECTION
* Spalted wood varies widely from board to board and source to source, so it is best to hand select each piece of wood for usability in regard to the project you have in mind. Watch for voids in the wood that could weaken its structure, depending upon where the void may end up in your project.
* Check the moisture content of each board and watch for pre-existing critters in the wood which could potentially infect other wood nearby.
* Because spalted wood may not be as sturdy as other species, it is generally used for accents, trim and small turnings. It is not recommended for larger pieces or joinery.
* Be careful in selecting the wood used for making kitchen utensils, food storage containers or toys an infant might chew on, since heat, moisture and time stimulate the release of the toxins found in some of these types of wood.
Photo courtesy of Woodcraft Magazine
IN THE SHOP
* While you don’t want to use wood that is too spongy for woodworking or turning, you may be able to harden small, soft spots of spalting with easy-to-find products. Wood must be dried completely to stop the spalting. For small areas, thin CA glue will do the trick. For larger projects, you can use Pentacryl to wick away the moisture from your blank. For very soft/punky wood, try System Three Rot Fix to penetrate deeper into the deteriorated wood.
* With soft and unpredictable wood, you’ll want to make sure those cracks and voids are filled for better, less frustrating, results. Use sharp tools to minimize tear-out and avoid running boards through the jointer, planer or table saw.
* Be mindful of differing surface hardnesses when planing and sanding spalted wood. Softer spots will get sanded away more quickly than more stable wood, so your best bet is hand-sanding when possible.
* Spalted wood is “thirsty” so remember that dyes and finishes may get soaked up unevenly. It may also require more coats to create the desired finish than on more stable wood. Some finishes can also darken the wood, so use clear if you really want to show off the dramatic patterns in the wood.
HOW SAFE IS IT?
* Though it’s always good practice to wear a dust mask when woodworking, it’s best to err on the side of caution when working with spalted wood that has not been stabilized or kiln dried. It’s generally considered about as harmful as any other wood dust, but folks with a lower tolerance for environmental toxins should wear a respirator and use a dust collection system. Just remember the dust will remain airborne for some time after you turn off your machinery.
* We recommend avoiding prolonged contact with your skin and cleaning your work area thoroughly.
For more information on spalted woods, check out this article from Woodcraft Magazine, “WoodSense: Spotlight on Spalted Wood.”
Another great resource is this book from Schiffer Publishing, Spalted Wood: The History, Science, and Art of a Unique Material.
