Grain direction of the paper
How important is the grain direction while printing? how can one figure out the grain and how is the planning of the job to be done?
Does grain direction effect binding more or printing also as much
I can't speak for offset work but for digital work the grain direction plays a role in how well it runs through the printer. For instance running 12x18 sheets (grain direction 18") will produce flatter output since the grain direction makes the sheet stiffer while running through. However depending on the sheet I've noticed that it also tends to jam more since it won't curl as easily to round corners in the equipment. 12" grain direction would curl more requiring some sort of decurler to flatten the output. This is probably not noticeable on text weight sheets but more on cover weights.
As you noted the grain direction is much more important in binding and finishing. Scoring/Creasing should be done with the grain in mind for the best possible outcome and you'll get better page pulls on binding if the grain is parallel to the spine of the book. When folding you'll also get cleaner folds when taking this into account.
The grain direction on a sheet is represented by the second measurement. For instance paper that is 23x35 has the grain running in the 35" direction. It can also be represented by underlining the dimension that is the grain direction. I've been told to think of grain as a row of pencils placed side by side to make up a sheet, obviously folding perpendicular to the pencils will force the pencils to break (wrong grain direction for folding) and folding parallel to the pencils is much easier.
You can determine the grain direction of an unknown sheet usually by folding it both directions and checking for cracking and roughness on the folded edge. The smoother of the two folds will indicate the grain direction. This is not always easy to tell though depending on the weight of paper and it's type.
grain direction is extremely important to how the final piece turns out. trying to print multicolor tight register work can be much more difficult if the grain is not correct. there will also be issues in the bindery when folding. sometimes a job printed on wrong grain paper will require additional post press operations in order to have the job fold without cracking.
the easist way to determine grain direction is to look at the carton or the skid. if the skid is labeled 25X38 it means that the grain goes in the 38 inch direction. if it goes in the 25 inch direction it will be labled 38x25. you could also just hand fold a sheet. you will get a much cleaner fold in the direction of the grain.
My primary concern with grain direction is for the press operator not the bindery guy. Grain should be parallel to the grippers. If you run a DI it would be grain short if you run a Speed Master it would be long grain. We have actually seen that scoring and folding against the grain produces a better score then going with the grain. Our thoughts on this is that if the sheet is not square when being cut from the folio sheet the grain can be a few degrees off from printing straight. this would cause an issue of the fold following the score or the grain when folding. When doing board or heavy card stocks you will get better fit and less slapping using the correct grain.
To find the grain, either:
- wet the paper; it will curl parallel to the grain (i.e. the grain will run down the 'valley' or 'trough' that the paper makes)
- slide your fingernails, pinched, down the edges of the paper. The side parallel to the grain will remain quite straight, whereas across the grain side will become wavy.
- tear the paper in either direction; the tear parallel to the grain will be straighter and neater than the tear across the grain, which will go skew and be jagged. (Most noticeable with newsprint.)
- simply bend the paper; bending against the grain, the paper will be stiffer - think of it like a bamboo sushi rolling matt, where the 'skewers' are like the grain of the paper. (Most noticeable with heavier papers.)
The wetting method works best when the water is applied to one side of the paper only,
The grain direction can impact your register for the print run. Short grain paper tends to move more.
Also, if you're running labels, grain direction may be EXTREMELY important to the client. Some labeling lines have very specific grain requirements.
In my experience if you run a DI short grain you are at the mercy of paper stretch, which as you have already imaged your plates could result in fit problems
Originally Posted by RGPW17100
On a DI it's suggested that you run long grain on text weight stock and short grain on cover stock. We followed this rule for the 5 years we had our DI and we never had any problems.
Originally Posted by stu
We're assuming a DI is fed portrait-wise, right? And, obviously, a SM landscape...