Because the stock jet and the wire travel the same way, more fibers line up along the machine direction, which gives the sheet its grain. Paper is stiffer and stronger along the grain and swells more across it when moisture changes. Grain also matters for optical work, because gloss, smoothness and readings taken with directional geometry often differ along and across it.
Heard on the job
Cut it grain parallel to the spine or the bindery will send the whole job back.
Insider tip
Tear a sheet both ways: it tears straighter and more easily along the grain, a quick check when the label is missing.
Also heard as
- grain direction