Tim was nice enough to give me some Water Oak from a tree that he had cut down and as you know I can’t say no to free wood. I split the logs into slabs and then cut squat cylinders (pucks maybe). I let some of these dry in this form and others I turned into rough bowls. At this point I was sealing the bowls and setting them out to dry but cracks started to develop. My next great plan was to turn some of the pieces down and heavily shellac them in hopes they wouldn’t crack.
If you’re not aware, wood moves depending on the moisture content in it. If you have real furniture, not Ikea veneered particle board stuff or plywood stuff, but real 100% wood you might have noticed. Well, the same things happens with wooden bowls. Since the moisture content in freshly cut wood is much higher than dried wood it moves a lot more than the seasonal movement of furniture. As the wood dries it is stressed differently causing it to move but if the stress gets too high it will crack. To slow the rate of moisture loss down I thought I’d turn some bowls to finished shape and heavily shellac them to see what happened.
I made two bowls from the Water oak. One of them (bottom) has a bead around the lip of the bowl and is coated in about 10 coats of clear shellac. The other (top) is taller and coated in only 5 coats of shellac. When I made them they were perfectly round. That was about a month ago. Let’s see how they’ve changed. Notice they don’t look perfectly round any more? In fact the top one is quite elliptical in shape. The bottom one isn’t perfectly round anymore either.
Now, you might think that movement isn’t too bad and you’d be right. But the wood moves in other ways too. Lets look at the first bowl, flipped upside down, straight on. Notice how the outer edges of the bowl have slightly moved up?
If that’s tough to see let’s look at bowl number two. It’s much more apparent here. If you note the orientation of the grain in the picture’s you’ll see that the pith, or center of the tree, would have been right below the edge of the bowl in contact with the counter and the grain runs from front to back going into the picture. The edges which are lifted come from the part of the tree furthest away from the pith. As the wood dries the wood shrinks more further away from the center causing the edges to lift as seen below.
It’s not limited to the top of the bowl either. The bottom is now quite warped and the bowl rocks as a result of this.
Here’s a view looking from the top of the second bowl. It is wider (left to right) than it is tall (top to bottom) which is expected from the discussion above.
Technically, this experiment has been a success because the bowls haven’t cracked (yet). Unfortunately, I’m not sure who would want a bowl that rocks like a ship in a tropical storm. Maybe some strategically placed fuzzy feet would solve this…nah. Gotta learn some how. Anyways, now you have some idea how much wood can move.