The quality of any printed document is vital. Whether a brochure, book, business card or set of inkjet labels, the products you have professionally printed will pass through a number of hands during their lifetimes. Unfortunately, there is one ‘silent killer’ which can render your printed materials practically unusable if overlooked. This killer is not understanding how paper grain affects printed items.
Paper Manufacturing and Printing
During papermaking, pulp is spread across a wire, and paper grains – also known as fibres – align themselves in a single direction, according to how the paper machine moves. This direction will either be parallel to the longest dimension of the sheet, or to the short side of the paper. Grain short paper is the result when fibres align to the paper’s short side, where grain long indicates fibre alignment with the long side of the paper. The direction of the grain will ultimately depend on how that paper has been cut.
During the printing process, paper is exposed to a wide range of conditions that cause it to expand and contract. As well, any glues or moisture that happen to be present will also cause expansion and contraction. In fact, paper fibres running against the grain can expand and contract up to 400% more than those running with the grain.
How Grain Affects Paper After Folding
When folded in a direction that goes against paper grain, there is far less risk of structural damage to the paper. However, if the paper being folded is of a heavier weight, the paper surface can crack. Therefore, the best way to fold paper is by whichever grain direction is parallel to your desired fold or score.
When folding occurs parallel to the grain, far fewer paper fibres get broken, and the fold is much stronger. If there is any doubt, the theory can be tested at home, simply by folding light stock paper in each direction, and then examining the quality of the folds. The fold which will appear cleaner and smoother will be the one that was folded parallel to the paper grain.
Smooth Paper is the Ideal
All printing, including that of inkjet labels relies on paper smoothness. The smoother the paper being printed on, the higher the image and print quality will be. The rougher that a paper’s surface is, image quality in terms of half-tones and solids will suffer. Paper that’s extremely rough will not even hold ink; instead, the roughness will cause ink to flake off or disintegrate when rubbed.
Rough paper will also not display images or print correctly in terms of fineness; for example, if an image contains delicate lines or a font is in fancy scripted format, these details may not accurately display on rough paper. This is because the many varied surfaces of rough paper don’t allow it to come in close enough contact for ink to adhere to it.
Roughness can be worked with
A printing press cannot correct the surface irregularities which cause paper roughness. However, they can be worked with by the application of ink in higher densities. However, this may not necessarily prevent ink from rubbing or flaking off when handled.
Some inkjet labels such as those used on cartons may indicate their grain direction. But if the paper being used doesn’t indicate this, grain direction can be determined simply by looking at the numbers. For example, paper sizes are indicated in width by length format. So if you’re using 11×17 paper. The grain direction would be long, with the paper fibres going in the 17-inch direction. Other times, the long grain side of the paper may appear in bold font.
Many printing production errors can be completely avoided by paying attention to grain direction.