Finding the grain of a sheet of paper

The first notebook I made with a proper hard cover looked fine on the day I finished it. A week later the covers had curled outward like a pair of wings, and the pages refused to lie flat when opened. The problem was not my glue or my sewing. It was the grain of the paper, which I had not even heard of.

What grain is

Machine-made paper is formed from fibres suspended in water, which flow onto a moving mesh. Most of the fibres line up in the direction the machine runs. That alignment is the grain. Paper folds, bends and tears more easily along the grain than across it, and, crucially, it expands and shrinks more across the grain when it gets damp.

In a book, every sheet of paper, card and cloth should have its grain running parallel to the spine. When everything agrees, the book opens easily, the folds stay crisp, and the covers stay flat. When the grain runs the wrong way, the book resists you and the boards warp as glue dries.

Three simple tests

You do not need any equipment. I use these, often more than one to be sure.

The bend test. Lay a sheet on the table and gently curve one edge over to meet the opposite edge, without creasing. Press lightly and feel the resistance. Then try the other direction. The direction that bends more easily, with a softer, rounder curve, is the one where the grain runs parallel to the fold.

The tear test. On a scrap, tear a short strip in one direction, then in the other. Along the grain the tear is fairly straight and clean. Across the grain it wanders and looks ragged.

The damp test. Lightly dampen a corner of a scrap with a fingertip of water. The paper will curl, and the curl forms a tube whose axis runs parallel to the grain.

Long grain and short grain

Paper sellers often describe sheets as long grain or short grain, meaning the grain runs along the longer or shorter side. When I fold a large sheet in half to make pages, I need the grain to end up parallel to the fold. That means planning which way to cut before I start.

I now mark the grain direction lightly in pencil, with a small arrow, on the corner of every sheet I cut. It takes seconds and has saved me from many mistakes.

Board and cloth

Board for hard covers has grain too, though it is harder to feel. The bend test still works if you try it on a large piece; one direction flexes a bit more. Book cloth and paper used for covering boards should also run with the spine.

When it does not matter much

For a simple pamphlet with a soft cover, grain direction is less critical. The book is small and flexible. Once I moved on to multiple sections and glued covers, though, it became the most important detail of all.

A small habit

When I buy new paper, I test the grain of one sheet straight away and write it on the packet. Then I never have to wonder again. It feels like a small, fussy step, but books that open flat and stay flat for years are the reward.