On the Edge

Today’s picture is a look at some edge gluing. This is done when the width (across the grain) needs to be increased. For instance, this part is to a credenza that is 17” deep. Even if I could find a piece of wood 17” wide, I wouldn’t use it. It would be very vulnerable to cupping and warping. I would cut it and glue it.

The (not always infallible) solution to cupping and warping is to alternate the rings on the end. If you look at the end of a piece of wood, you can see the configuration of the rings. They either go down or up in most cases. Therefore, if you are gluing two pieces of wood together, you put one set of ring curves down and the others up. This alternation helps to keep the piece of wood you finally get fairly straight across.

The gluing process is always done on the side of the wood. That means whatever the direction of the grain of the wood the sides are parallel to it. In all rectangles that are cut with the grain, there will be two end grain sides and two sides. The end grain sides are the ones where the grain ends. These end grains cannot be glued very effectively. This is because wood is like a bunch of soda straws (as a friend of mine once said to me) stacked parallel to one another. These soda straws are channels in the wood that permit moisture and nutrients to flow along its length. Trying to glue the end grain would be just like attempting to glue soda straws together end to end.

One last point: if the wood is glued properly, there is no need to do anything else for it to stay together. No splines are needed. In fact, I’ve experimented and found that, when I tried to break a glued-up piece of wood, it broke at another place than the glue joint.

This is what life is like on the edge.