Grain Direction

What is grain direction?

Grain direction refers to the arrangement of fibre in a sheet of paper or card. When paper or card is made by machine, the wet fibre is agitated as it rolls along a conveyor belt. This vibration encourages the fibres to line up in the direction of travel – they tend to point in one direction. As paper fibre is resistant to folding, we get a noticeable difference if we try to fold paper, one way, then another (after a quarter turn).

Why do bookbinders care about this so much?

Folding paper is how we usually start to make a book. If we fold against the grain the folds will be lumpy and the pages will have a tendency to spring open. If we fold with the grain, the page folds will be more accurate, press neatly and the pages will have a greater tendency to flatten when the book is closed.

When paper is wet it stretches and it has a tendency to stretch more in one direction than another. (The paper fibres swell up as they absorb moisture and “fatten” rather than lengthen.) When the paper dries it will shrink back but not always back to its exact original size. When bookbinders add a layer of wet glue between two sheets of paper, card, board or paper-backed bookcloth, both the layers will stretch and shrink and if they are doing this in opposite directions, weird warping can happen. Generally not desirable in a book!

So bookbinders always try to get the grain direction of all materials running from head to tail in book, or parallel to the spine. Finding the grain direction of the paper or card is usually the first thing a bookbinder will do. Before they walk out of the shop with it!

How do I find the grain direction of my paper?

There are two quick tests you can do:

Take your sheet of paper or card and gently roll it in your hands. Then turn it around (quarter turn) and roll it in your hands again. Feel the difference! Does one way feel softer than the other, or easier to roll? If so you have found the grain direction of the paper and if you went on to fold that sheet in half you would have found your way to the spine fold.
The hangover test. For this testing method you need two sheets of the same paper. Take one sheet and hang about a third to half of it over the edge of your worktop. Find a suitable paper weight to hold it there. Then take the second sheet and give it a quarter turn and hang the same amount over the edge of the worktop. Weight it there. Compare the drop. The sheet that drops the furthest indicates the easier way to fold. So in this photo, the sheet in front is showing that the GD is the line made by the edge of the worktop. Fold along this line and you have your spine fold.
Tip: Most A4 paper is long grain. This means that the GD is parallel to the long edge. So when you fold your A4 printed sheets in half to A5 you are normally folding against the grain which makes the paper a bit bouncy! Press harder to flatten the sheets.

Another tip: if you need paper for endpapers, which are going to be glued to the inside of a hard cover, choose larger sheets of paper to cut them from so that you can get the GD going the right way.

Another tip: once you have found the GD of your sheet, pencil a small arrow in one of the corners as a reminder.

Need more explanation? This site looks as good as any.

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