We have all probably heard that grain direction is important, though maybe we’re a bit hazy about why.

The grain direction is fixed in the paper-making process. Pulp is poured onto a web traveling rapidly forward; joggling around on it, the pulp (a mixture of cellulose fibers and 98% water) will naturally arrange itself with the fibers running parallel to the direction of travel. The grain direction is the direction in which the fibers are lying.

Grain direction is important because (in an ideal book world) the grain direction of the text, the endpaper, and the board should all be the same, parallel to the spine of the book. This is because paper is easier to fold along the grain, and if moisture is picked up all the elements will react similarly and cockle across the top dimension (usually the shorter one) rather than struggling against one another.

Determining grain dimension is relatively straightforward: just tear the sheet. You’ll get a long clean tear with the grain, and a raggedy back and forth against the grain. This works fine with newsprint or disposables, but if you value your product, gentler methods may be superior. Here, from Bookbinder’s Chronicle is a video showing two non-destructive methods.