Understanding Grain Direction in Photo & Art Papers

Should I Care About Grain Direction?

The primary people who need to be concerned about grain direction are those making books.  More specifically, people making books that are bound so that the spine holds the book together AND the paper needs to be folded as the book closes. 

For books that use comb binding, wire binding, three-ring binding, and similar methods, grain direction is irrelevant. 

In addition, if you plan to fold your paper for any reason, knowing the grain direction can be helpful so that the paper lies as flat as possible when folded.  Will terrible things happen if you fold against the grain? No. It is a nice thing to know and use but folding with the grain is certainly not a requirement.

What Does Grain Direction Have to Do with Folding Paper?

For the easiest folding, and a fold that allows a book to stay open without springing closed, you want the fold line to run parallel with the grain direction.

Grain direction is related to how easily a paper will bend in a certain direction.

Grain Long (GL): For books in vertical orientation
Grain Short (GS): For books in horizontal orientation

What About Paper Weight? Does that Make Any Difference?

It does.  Heavy and thick paper will be cumbersome to fold regardless of grain direction.  Lighter and thinner papers fold easier and grain direction will be important in book binding situations. See above.