WoodSense: Spotlight on Bubinga

A particular quote from Winston Churchill begins “Solitary trees, if they grow at all, grow big and strong…” He could easily have found his inspiration in bubinga trees. These trees often grow alone, or in small copses. They can reach towering heights of 150′ or more with 3-6′ diameter trunks. Often the first branches are 60′ up, which makes for remarkably clear lumber. Fortunately, these trees usually grow near water, so the massive logs can be floated out rather than dragged out of the forest to be milled. Because of the size and weight of the lumber, much bubinga is cut into veneer for easier shipping. In Europe, where much of the veneer winds up, bubinga is known as kevazingo.

Those logs that are cut into lumber can yield some staggeringly large, live-edged flitches 5-6′ wide and up to 20′ long. (Think ostentatious corporate boardroom table.) Luckily for those of us mere woodworking mortals, some logs are milled into “normal” widths and lengths perfect for most furniture projects. The wood itself ranges in color from pinkish to brick red, with darker purple or black streaks. The sapwood is much paler and contrasts sharply with the heartwood. The grain can vary from straight to highly-figured. Expect to pay a premium for pieces displaying curly, pommele, flamed, waterfall, and quilted figure.

Where the wood comes from

While only about a fifth of Africa is considered forested, that 20% yields some truly awe-inspiring trees. Among these are three species which give us bubinga—Guibourtia spp. (G. demeusei, G. pellegriniana, G. tessmannii). Bubinga trees grow in the rainforests of western Africa, mainly in the countries of Gabon, Congo, and Angola. The trees prefer wet areas such as swamps, or lake and river banks. As of this writing, bubinga is not listed on the IUCN (International Union for Conservation of Nature) red list of Threatened Species. It is, however, mentioned in the CITES (Convention on International Trade in Endangered Species) Appendix II. This list targets species that aren’t threatened per se, but warrant careful monitoring lest they become so.

History in woodworking

Since the 18th Century, woodworkers have prized bubinga for its rich color and fantastic figure. French Renaissance furniture makers dubbed it “bois de rose d’Afrique” or “African Rosewood” and frequently incorporated it into high-end pieces for their wealthy patrons. While it is not botanically a true rosewood, the name lingers on.

Selecting the best stock

As with most exotic species, bubinga isn’t something you’ll find at a big box home improvement store. However, even extra-long and wide boards are available through specialty hardwood retailers, though at additional expense. Because bubinga often boasts beautiful figure (again, at a premium price), it’s worth asking for photos if you’re buying online for a specific project. Expect to pay about $13/board foot for typical boards; for larger widths and highly-figured pieces, the price can easily surpass $30/bd. ft.

A red palette and varied grain. Bubinga ranges in color from pink to red and is characterized by dark streaks throughout. The grain varies from straight to wavy.

Working bubinga

Bubinga is quite hard, so make sure your tools are very sharp, especially power saw blades and router bits, which can otherwise leave troublesome scorch marks that must be sanded out. Embedded silica grit in some bubinga lumber can wreak havoc on jointer and planer knives, so be prepared to swap them out after machining bubinga. The interlocking or rowed grain on some boards may make cutting with the grain impossible. In this case, a sharp card scraper may be the answer.

When cutting joinery, you’ll need to be very precise. Unlike some woods that will compress somewhat under pressure, bubinga has no give. If you force a joint that is a little too tight, something will break. Like many exotics, bubinga contains natural oils that can impede glue adhesion. As a precaution, wipe glue surfaces with alcohol immediately before assembly.

In addition to its beauty, bubinga is also quite tough and strong. In fact, several high-end tool companies use it for their chisel handles, plane totes, etc. You may find that it’s a good wear-resistant material for jig parts such as the runners on table saw sleds. But because of its hardness, bubinga doesn’t carve particularly well with traditional carving tools. If you really need to carve it, you’ll have better luck with rotary burrs rather than gouges or knives.

Finishing

Although bubinga accepts stain and finish well, I’m not sure why you’d want to stain it. You may find a better-looking surface by sanding to a fairly high grit, like 320 to 400. For figured stock, oil-based wiping varnish tends to make the swirling grain “pop.”

Bubinga: Working Notes

One of my test boards was the nice 8/4 piece shown on the facing page. It was beautiful but had some significant snipe marks across its end. Thinking a few quick swipes with my old Bailey #5 would remedy the problem, I dogged the board to my bench and had at it. But my plane just skated across the surface, as if I was planing a piece of plate glass. Hmmm? This was obviously not like a piece of cherry. I resharpened the blade, set the plane for a very light pass, and tried again. More skating. What is this stuff? I altered my stance and applied more downward pressure. Ah, there’s a shaving. A nice thin one, too.

Okay, I’m getting the hang of this, as well as some cardio. Slowly the board gave up its snipe marks. On to scraping and sanding. It scraped beautifully, and sanded quickly—80-grit, 120, then 220. I think bubinga’s hardness works in its favor when it comes to sanding. Even the end grain polished nicely. I can work with this.

The other samples cleaned up nicely, too. I was glad I didn’t have to edge glue them, as the color and grain pattern varied significantly. The 8/4 piece was a rich purplish-red, almost a dark raspberry color. In contrast, the other sample boards were more on the orange side—their color reminded me of an adolescent penny. So if you plan to build a piece from bubinga, it behooves you to carefully select your boards.

I made the boxes below by routing out their interiors and turning the lids. Bubinga turns well, though I had to be gentle, as aggressive cuts with a bowl gouge really grabbed. Routing was a joy (as much as routing can be). Even with a moderately used roundover bit, the edges came out crisp with very little tearout, even across the end grain. I finished up with three coats of a wiping varnish, rubbing with steel wool in between. Bubinga has certainly earned a spot on my lumber rack.

 


Woodcraft
Article by: Ken Burton

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