The following are general descriptions of some of the basic characteristics of paper.
- Basis Weight is the weight of a ream of paper in the Basic Size for that grade (e.g. 500 sheets of Sub. 20 Bond paper in its basic size 17 x 22 in. would weigh 20 lb.) Sometimes the same paper is assigned two basis weights e.g. 24/60, meaning the same paper is sold in two different basic sizes; 24 lb. Bond (basis size 17” x 22”) which is approximately the same weight as 60 lb. Text or offset (basis size 25” x 38”). Note that basis weight in “pounds” is used mostly in North America. Outside of North America, paper weight is usually specified in grams per meter squared (g/m2).
- Caliper refers to the thickness of the paper in thousandths of an inch, or mils. Why does 500 17” x 22” sheets of 50 lb. Offset paper weigh the same as an equal amount of same size sheets of 20 lb. Bond? Why do equal quantities and sized sheets of 90 lb. Index and 100 lb. Tag weigh the same? The reason is thickness. Thickness means only that. It doesn’t mean heavy or light. A heavy sheet can be made heavy by the addition of coatings. So, caliper is only a measure of thickness. As an example, 50 lb. Offset can vary in caliper from .0013” to .0032” thick. Paper that is too high in either basis weight or caliper can cause misfeeding from the paper tray and paper jams in the paper path.
- Finish or Texture, refers to the surface smoothness of the paper. Paper that is too rough will wear out pick-up rollers, paper guides, and other components on the paper path prematurely. A rough surface finish also degrades the quality of printed output. The peaks and valleys on the paper cause poor toner adhesion, a striped appearance, or characters that have broken corners. Paper that is too smooth results in misfeeds, poor toner adhesion, and washout.
- Grain – During the paper manufacturing process, paper fibers are predominantly oriented in one direction, known as the grain direction of paper. Long grain paper has the grain direction running parallel to its longer dimension, and is the recommended choice for LTR direction. Also note the actual feed direction or placement of paper. Even though LTR is preferred long grain, the direction of feed is “short grain side”. Paper is normally stiffer in the grain direction. A little known fact is that a paper supplier can custom produce (cut) paper in the desired grain direction for a nominal increase in cost. When faced with a customer’s paper choice that does not yield satisfactory results, this approach might just “save the day”.
- Opacity – The degree to which images printed on the opposite side of a page can be seen. Generally, the thicker the sheet, the more opaque it is. However, with the addition of mineral fillers such as titanium dioxide, any paper can be made more opaque.
- Gain Curl – The measurement of the curl of the paper. Gain curl measures the highest point of a sheet of paper when it is laid flat on a surface.
- Cut Edge Condition – Refers to the smoothness of the edge surrounding that paper. If the edges are too rough, multi-feeds can occur.