#77: Balsa

Bird number: 110
Date: October 11, 2012
Wood: Balsa (Ochroma  pyramidale)
Source: Hobby Lobby

I suspect most people have done something with Balsa wood. I know that when I was a kid lots of things were made from it, including model airplanes, pieces of model rockets, and building models (bridges, skyscrapers, etc.). The local hobby store had a huge stock of the stuff in many different widths and thicknesses. It’s difficult to find a hobby store these days that has a similar stock of Balsa wood, but places like Michael’s and Hobby Lobby always have some of the stuff. And of course you can get just about any size online. I picked up this piece at Hobby Lobby. I was a little surprised that I could buy such a large piece (it was about 2.5″ x 2.5″ x 12″). I don’t recall seeing Balsa in anything larger than 1/4″ thickness before.

Balsa is very light. Average density is about 175 kilograms per cubic meter: less than 20% the density of water. Balsa is much stronger than its light weight would indicate. It’s the preferred material for modeling. The de Havilland Mosquito, a World War II light bomber, had Balsa wood wings. The wood is also used as core material for composites, including the blades of many wind turbines, the floor pan of the fifth generation Chevrolet Corvette (1997-2004), and many surf boards. Thor Heyerdahl made his raft Kon-Tiki from Balsa logs.

The Wikipedia article says that Balsa is a popular wood for whittling. I find that unlikely. Of all the carvers I’ve met in the last four years, few have even tried carving Balsa, and not one of them had anything good to say about it. Most said that they gave up before completing a project, and nobody said that they’d carved more than one piece from Balsa.

Carving Balsa requires a very sharp and very thin knife (think of an X-Acto knife), a careful hand, and small slicing cuts. The wood fibers will crush rather than cut if you try to push the knife through it. It’s distressingly easy to apply a little too much pressure and end up slicing off something important. In addition, you can’t use the wood itself to stop the knife as you can with a harder wood. An uncontrolled cut will go right through the wood and into your hand. Also, the wood is so soft that it doesn’t take detail well. The beak on this bird is very short because the longer and thinner beak broke off. Balsa just isn’t a good material for carving.

Sanding, too, requires a lot of care. It takes only one or two passes over a high spot to turn it into a low spot. Like carving, you have to be very careful not to take off too much. I’m pretty sure that, given a piece of 120 grit sandpaper and an hour, I could sand one of these birds from a block of Balsa wood.

It was an interesting challenge, and the finished product has a bit more character than I expected. The brown specks make for an interesting texture. I can now say that I’ve carved something from Balsa wood, and I don’t think I’ll need to carve anything else from it.