Paper grain,
explained.
As paper is made, its fibres line up parallel to the direction of travel of the paper machine. This is the grain direction. It determines how the paper folds, how the pages of a publication turn and how much the sheet changes size with humidity.
How it is formed
On the paper machine the pulp is spread onto a moving wire. As the water drains, most fibres align with the direction of travel, the machine direction (MD). The direction at right angles to it is the cross direction (CD). Paper does not behave the same way in both: it is stiffer along the grain and expands more across it.
Fibres follow the direction of travel of the paper machine (MD).
Long grain and short grain
Long grain
In a 70 × 100 cm sheet the fibres run parallel to the 100 cm edge. In sheet sizes the grain direction is usually given by the second dimension, or underlined.
Short grain
The same sheet written as 100 × 70 cm has its grain parallel to the 70 cm edge. Same paper, different behaviour in folding and binding.
Where it matters
| Stage | With the grain | Across the grain |
|---|---|---|
| Folding | A clean, straight fold. | Fibres break and the coating and ink crack, most visibly on heavier stock and dark solid colour. |
| Binding | With the grain parallel to the spine, pages turn easily and lie flat. | Pages resist opening, the spine ripples and the book will not stay open. |
| Dimensions | Small change with humidity. | The sheet expands two to three times more, which affects colour register. |
| Stiffness | The sheet stands up and does not droop. | The sheet flops. Important for cards, covers and hanging pieces. |
This is why, in offset printing, the sheet is normally fed with the grain parallel to the cylinder axis, so that paper expansion does not disturb the register of the four colours.
How it is identified
The grain direction is stated on the label of every pallet and ream of paper and is confirmed at the printer before cutting and folding. The simplest check is flexing: the sheet bends with less resistance when the curve runs parallel to the grain.
The rule by product
Books, catalogues, magazines. Grain parallel to the spine, without exception.
Folded leaflets. Grain parallel to the fold line. In cross folds, the last fold takes priority.
Cards, covers, folders. Grain parallel to the spine or the crease. See also the fold types.
Two-sided work with tight register. The same grain direction across the run and on every reprint.
We set the grain direction when each job is planned, according to the fold, the binding and the paper. Your file needs no adjustment.
Frequently asked questions
What do long grain and short grain mean?
Long grain: the fibres run parallel to the long edge of the sheet. Short grain: parallel to the short edge. The same paper is usually available both ways, and the choice depends on the product.
Why does paper crack at the fold?
Because the fold runs across the grain, or because the stock is heavy and has not been creased. Heavier papers and board are always creased before folding.
Do I need to state the grain direction when ordering?
No. We choose it according to the fold and binding of the piece. If the job has to match an existing publication or has a special requirement, mention it in your quote request.
Send us the specifications of your job.
Size, quantity, material and number of colours. We reply with a technical proposal and a quote.