It pretty much is due to the stresses it grows under. When a tree is small, there is a relatively small amount of wood growth to a ring; once the circumference bocomes large, the amount of wood needed to create a ring is multiplied greatly. This growth happens, and sometimes the growth has to grow against another growing part, say like in a "crotch" point or at the point where the tree meets the dirt and and has the weight of the tree sitting on top of it. The wood goes where it can, causing waves and uneven rings and, in my opinion, burling. Sometimes there is no room to move, and the stress generates some beautiful patterns from tensioned and compressed wood fibers. It happens to other trees as well as maple, it's just that maples do it very well.
I ask this question about 20 years ago of Dr Lamb of Va Tech college, he was considered the leading authority, he sent me a stack of papers about 3 Inches high on stuff he had researched and written, it conculded , they have no idea, but a zillion theories , from experience I can tell you , you can get 20 experts together and you will have 48 opinions… just be thankful it does and enjoy the wood
I've handled it all of my life in the saw mill. I always say it's of undetermined cause and Charles is correct about everyone's opinion in that they mostly differ. However, my theory is similar to Nomad62's. I think it starts very early with the sprout against a rock or another root, the ripple effect is then carried through out it's growth. I've heard wind, moisture, bird and a number more.
Wow, fascinating. I didn't realize it was still a mystery. As far as the price, I'm very clear mtnwild, that's why I was hoping it was possible to create different types of figuring. Then again I'm sure if you could they wouldn't be so expensive. Thanks everybody for replying.
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