Paper is made from wood; this isn’t breaking news, and like wood paper has a grain. The direction the grain runs plays a large roll when you are printing and folding paper. It is much easier, and cleaner to fold a piece of paper with the grain than it is against it. A commercial printer will try to fold paper with the grain, although this is not always possible. Folding against the grain is not forbidden, but it can change the look of your project. Folding against the grain will cause the paper to crack, and possibly distort the image printed.
Knowing Which Way the Grain Runs
The terms to know when talking about grain on paper are Short Grain and Long Grain. If you fold a sheet of paper along the “short grain” you are going against the grain, and you are going with the grain if you fold it along the “long grain”. For most sheets of paper the long grain runs parallel to the long edge of the sheet. This is the default position, but there is paper that does not follow this rule. If you happen to have a square sheet of paper there are a few ways to tell which way the grain runs:
Take A Look:
If you look closely at the sheet of paper you may be able to see or feel the grain on the paper, however, the thinner the paper the more difficult it is to tell which way the grain runs. If you can’t see which way it runs try tearing it.
If you rip a piece of paper it will tear much cleaner with the grain than it will against it. Take a look at the image of the torn paper above. The longer pieces have a straighter edge because they are going with the grain as opposed to against it. You could also try folding it.
It is easier to fold paper with the grain than against it. Also the edge will lay flatter because it does not have to brake the paper fibers to fold with the grain. On a fold against the grain the paper will crack and look rough.
You might be wondering why it makes a difference which way the grain runs. If you are printed something that folds or bends it can make a substantial difference. When you fold a sheet of paper it folds much easier with the grain, it also lays flatter, and the fold looks much cleaner.
If you fold against the grain the paper will crack, this is especially important if you have a lot of color or an image that crosses over the fold. The cracking from the fold can distort the image, and if there are solid colors you will see the white of the paper on the fold. This can be helped by “scoring” the paper before the fold, but it works much better to fold the paper with the grain.
Things to Remember
When folding a sheet of paper, it will fold easier, and look better if you fold it with the grain. You can tell which way the grain runs on the sheet by using the tear, or wear test, or by just looking closely at the sheet. If you are printing with solid colors or images that run over a fold, it should be done with the grain to avoid cracking. If you need to have a fold that goes against the grain it should be scored first.