Repairing a Cracked Shelf

Q We have a split in the wood on the bottom shelf of our sideboard. It’s almost a quarter inch wide in some places and runs the length of the board, about 30 inches. The split is curved and appears to follow the curve of the wood grain. We removed the back of the sideboard and tried squeezing the crack together with a couple of bar clamps to no avail. The doors and back panel do not seem to be affected by the split. What can we do to repair the crack? Can we just fill it?

A From your description of the crack and the location (inside bottom shelf), it sounds to me like it is a grain check (a crack that follows the grain of the wood) rather than a seam split. I would guess that the boards which comprise this inside bottom shelf are plainsawn oak rather than quartersawn, since plainsawn boards are more likely to warp and check. Filling the crack with wood filler would be a temporary fix, because wood filler has little or no gluing power; as the crack expands and contracts with seasonal changes, the filler will let go on one or both sides of the split. Instead, I would stabilize the crack with slow-set (24-hour) epoxy.

Start by taping the edges of the crack with blue masking tape (it’s easier to clean the excess epoxy from the tape than from the wood). If the crack goes all the way through the board, you should also tape the bottom of the crack to prevent epoxy from leaking through. Put enough epoxy in the crack to fill it almost to the top, leaving about a 1/16th of an inch unfilled. Pull the masking tape off the top, let the epoxy harden overnight, and fill the remaining 1/16th of an inch with conventional filler, which is easier to stain than the epoxy. The epoxy will stabilize the crack; it also works well to stabilize knots.