Woodsense: Spotlight on TamarindComments (0)
This article is from Issue 78 of Woodcraft Magazine.
Add spice to your next project with this spalted wood
By Joe Hurst-Wajszczuk
Until recently, not much was known about tamarind (Tamarindus indica) outside of its home turf. Despite the value of its lumber and fruit, this species warrants little or no mention in most woodworking books. Due in part to growing interest in sustainable, responsibly-sourced lumber (as well as adventurous appetites), this tree is beginning to enjoy a wider worldwide audience.
Unlike most woods, tamarind’s appeal is not based on its harder, darker heartwood, but on its less durable sapwood that’s an attractive meal for fungi and insects. When the timing’s right, Mother Nature’s attack on the creamy outer layer induces spalting, an early stage of decay that creates dark-colored veins, transforming even the smallest blank into a unique work of art.
This stripey wood has its share of challenges, but understanding how to select and use the best material will reward you with spectacular results. Read on to discover how to make the most of this rare lumber.
A not-so secret ingredient
A large tamarind tree can produce nearly 400 pounds of fruit annually. The sticky pulp of the pod-like fruit is a staple in Middle Eastern, Mediterranean, and Asian cooking. Used fresh or dried, it plays a potent role in all sorts of savory stews, soups, and condiments, and is enjoyed as a tangy, sugar-coated candy. In addition, the pulp serves as a traditional medicine and meat tenderizer. In fact, it may be in your own fridge, since the extract is an ingredient in Worcestershire sauce.
Where the wood comes from
This modest-sized tree (averaging 80' tall and 30" in diameter) originated in Africa, but today thrives in tropical regions across the globe, including Southeast Asia, China, Mexico, and southern Florida. In frost-free climates, tamarinds are commonly planted as ornamentals, and sometimes cultivated as miniature bonsai trees.
History in woodworking
The fruit of the tree has been used for centuries for both cooking and cleaning. (The tartaric acid in its pulp is an effective polish for copper and brass.) Although the lumber doesn’t have a lengthy resume, it has been used locally for items ranging from furniture to farm implements. Large branches and trunks are sometimes simply crosscut through and used as chopping blocks, partially because these end-grain slabs cause less damage to cutting tools than do flat-sawn boards.
How to select the best stock
Tamarind’s deep-red heartwood is very durable, but it’s only found in the oldest and largest trees, and is difficult to work. Because of that, it doesn’t enjoy the same utility as the less durable, but readily available sapwood. Much of this wood comes from found logs, branches, and small trunks cut and left to rot on the forest floor. Because the spalting process is far from scientific, it’s important to handpick each board or blank to make sure that you’re getting the desired effect. (See photo, above.)
At approximately $23/bd. ft., tamarind’s cost is on par with many top-shelf exotics. As a result, its use is often limited to small projects like bottle stoppers, pens, and bowls. If you care to taste-test this wood, smaller turning blanks start at $5. For additional flair, you can purchase through-dyed blanks for a few dollars more. Resin-stabilized blanks, like the samples shown bottom right, eliminate the risk of failure associated with working partially decayed wood. Although the process makes the wood ideal for knife scales and pens, stabilization doubles the material’s cost, and is limited to smaller-scale stock.
Working tamarind in the shop
Because of its density and interlocked grain, tamarind’s heartwood is notoriously difficult to work. However, the softer sapwood is somewhat friendlier. Although it has a moderate blunting effect on steel-edged tools, it succumbs easily to carbide. But use only clean, sharp cutters to prevent tearout and scorching, and take quick, light passes when machining the wood. As for gluing, you shouldn’t have any problems.
Tamarind turns well with sharp tools, but is subject to the same challenges as any spalted wood. That is, you can expect to encounter soft, punky sections, so keep your tools razor-sharp to minimize tearout. You can stabilize punky areas with two-part epoxy or cyanoacrylate (CA) glue, and then rehone your tools and finish up with a light touch.
The wood itself is not reported to cause allergic reactions, but the spalting might warrant precautions. For healthy adults, fungal spores are about as harmful as wood dust, so a dust mask and dust collection typically offer adequate protection. However, people with immune system disorders should not work with any spalted wood.
Tamarind’s diffuse-porous grain structure and soft fungal streaking make it an excellent candidate for dyeing and resin stabilization. However, those same characteristics cause the wood to absorb finish like a sponge before establishing a consistent surface film. Pre-treating the softest spots with shellac or CA glue can help. Tamarind accepts all finishes well, but to best preserve the contrast between the creamy white sapwood and dark fungal streaks, use lacquer or a water-based product.
Stabilized blanks are a different story. The resin impregnation process seals the cells of the wood, causing these blanks to behave more like plastic. So, as with an acrylic turning blank, sand up to your finest grit, and then power-buff the finish to a fine luster.
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