Paper grain refers to the direction in which the majority of the cellulose fibers in paper are aligned. During the papermaking process, the fibers tend to align in one direction in the production line. This direction is the grain.
There are two types of grain directions:
- Long Grain: The fibers are aligned parallel to the longest edge of the paper. Paper with long grain tends to be more flexible and folds more easily from top to bottom.
- Short Grain: The fibers are aligned parallel to the shortest edge of the paper. Paper with short grain tends to be stiffer and folds more easily from left to right.
The grain direction can impact several properties of the paper such as its strength, flexibility, how it absorbs ink, how well it folds, how it reacts to changes in humidity, and even how it feels to the touch.
When printing or binding books, it’s important to consider the grain direction because paper tends to expand and contract with changes in moisture along the grain. So for a book to open properly without cracking or tearing at the spine, the grain of the paper should run parallel to the spine.
The grain direction of the paper is typically represented by the second measurement in the dimensions given. If the paper is listed as 12×18, this means that the grain runs in the 18″ direction. This is because the grain direction is usually long, meaning it goes along the longer dimension of the paper. When you see a larger number first, like 18×12, the grain would be running in the short (12″) direction.
Please note that these are general rules and can vary depending on the type of paper and manufacturer. It’s always a good idea to check with the paper supplier if you’re unsure.