All paper and book cloth has a dominate grain. It’s important to know the grain direction before you start your book repair, so here are the most popular methods for determining the dominant grain in either paper or book cloth.
Paper can be tested for grain using the bend test, the tear test or the water test. The grain of book cloth usually runs parallel to the selvage or bound edge of the fabric. If the selvage of the book cloth has been cut off or if there is any doubt about the grain of book cloth, the bend test or the tear test can be used to determine the grain.
The quickest way to test the grain is to bend the paper or cloth slightly in each direction. Bring two opposite edges of a piece of paper or cloth together but do not crease. Instead, gently press down on the bend with minimal pressure. Feel any resistance. Now bring the other two opposite sides of the paper or cloth together and repeat the process.
In one direction there is more resistance than the other. The greater
resistance means the paper or cloth does not want to bend in that direction because it is bending against the grain.
When the paper or cloth is bent in the opposite direction, there is much less resistance. The bend that offers the least resistance is the bend that goes with the grain of the paper or book cloth.
Mark the direction of grain on the paper or book cloth for future reference.
Another way to test for the grain is to tear the paper or cloth. Paper or cloth will tear easily and straight along the direction of the grain. When forced to tear against the grain, the paper or cloth will be difficult to tear and the tear will tend to curve until it meets the grain. Tear the cloth or paper close to a comer and then pencil a small straight line in that corner indicating the direction of the grain so it won’t need to be determined every time it is used.
When grain is particularly difficult to find, a water test can be used. Use this test only to test paper being used to repair a volume, not on pages bound in a book. Draw a 4” straight line along one comer of a large sheet of paper. This line will not necessarily be the grain line, it is simply an orientation line. Cut a square out of the comer, including l/2 of the line. Moisten the small square of paper and lay it on a work surface. As the water is absorbed into the paper fibers, the square will begin to curl. The two edges that curl toward one another are parallel with the grain. Mark the correct grain on the square. Replace the curled square in position on the large sheet of paper (match the cut pencil line) and mark the correct grain on the large sheet. Remember, the first pencil line is not necessarily the grain line.