As knife makers, the figure of wood is an important consideration. Plain wood has very little value compared to the beautiful curls of Koa or maple. But how does this figure come about? And how can you maximize its appearance?
To understand this, you must first understand what wood figure is.
Simply put, wood figure is an outcome of the fact that wood end grain reflects light differently that wood face grain, and by varying the angle of the grain with the surface, a variety of effects can be observed.
First, let us consider a tree. While before I used the analogy of straws, no think of a tree as a series of tubes, one inside the other. This makes sense, as the cross section of a tree shows these rings, evidence of the tubes added year after year to the tree. In a tree with perfectly straight grain, each tube fits inside the other, its walls straight up and down yielding perfectly straight grain.
This image shows a quartersawn piece of curly wood. As you can see, the rings are not straight up and down, but rather unjulate back and forth in waves. This is where curl comes from. TO imagine what is causing this, think of the tubes making up a tree. Where before they were straight up and down, now each tube is wavy, each fitting against the next, interlocking their waves. Look at the none curly edge grain of a block of curly wood. You should noice squiggly lines of grain running the length of the block.
When this wood is cut perpendicular to the waves and planed, a surface like this is seen.
As you can see, the angle of the grain meeting the surface varies in a repeating pattern. And because the end grain reflects light differently than face grain, a pattern emerges. Across the surface of the block, light shines unevenly and thus gives yield to a curly figure.
Burls are special to knife makers. We love them more than any other craftsmen. And their beauty is palpable. But what is a burl? How do you maximize its beauty?
Well, there are two main types of burl. Grain burls and eye burls. Grain burls will often look like a brain, randomly formed grain with a smooth to slightly knobbly surface. These burls will lack the dramatic eyes that are loved. These burls tend to form around dead wood or at an injury as the tree attempts to grow over a wound.
The much more valued burls are eye burl. Their surface will often look covered in pins
This burl cap shows the tell tale pins of an eye burl. These burls are caused mainly by a bacterial infection. This bacteria creates a hormone that in trees induces budding. This hormone buildup causes the tree to form many small buds that due back and become encased in more buds. They tend to form from a single point. And emanate outward.
You can think of them as half of a sphere. The center of the flat side of sphere is the site of the infection, with many tubes radiating out from this point. If you were to cut a surface parallel to the flat of semi sphere, you would be rewarded with a surface full of eyes, as you would intersect the tubes of the burl. If you were to cut perpendicular to the flat of the burl, you would see a figure reminist of curly grain, as you slice the tubes of the buds in half along their width.