boule

A boule is a log that has been bandsaw-cut into thin parallel slices, then immediately restacked in their original sequence and orientation, creating a packet that looks almost like the uncut log from the outside. The edges remain waney, meaning the original bark line is preserved on the outer faces. When you open and unfold these slices, the grain pattern runs continuously across them, like pages in a book.

The sawing is done on a large vertical bandmill, typically producing 4/4 or 5/4 thickness stock in hardwoods. The slices come off the blade in order and are stacked without rotation or reversal. This is the opposite of flatsawing, where a log is simply cut parallel to a line through its center, or quartersawing, where the log is first divided into quarters. A boule's main advantage is radial grain matching: consecutive slices show the same growth ring pattern at similar angles, which is invaluable for matching appearance in tabletops, veneer sequences, or decorative panels.

The waney edges are both a feature and a constraint. They preserve visual authenticity and allow the woodworker to use the live edge if desired, but they also mean the board width varies along its length and the edges require handling. Much of the wood in the outer slices is lost to waste because of taper and wane. A boule from a 16-inch diameter oak log might yield only 60 to 70 percent usable straight-edged lumber.

Boules are most common in hardwood mills serving the furniture and architectural millwork trades. Red oak, white oak, walnut, and maple are frequently sold this way. The stacked form makes shipping efficient and keeps the grain sequence intact for the buyer. A boule may contain 20 to 50 slices depending on log diameter and target thickness. Once delivered, the woodworker typically unstacks them gradually as needed, storing the rest in a climate-controlled kiln or conditioning room to minimize cupping and checking.

The term comes from French and refers to the shape of the bundle. It is sometimes called a book-matched log in North American usage, though that term is imprecise. Sawyers must take care during the cut to keep blade deflection minimal, otherwise the slices will not stack flush and the grain match will be ruined. Blade tension, feed rate, and log clamping are critical to boule quality.