What characteristics should you consider when choosing paper for your printed product? Here are the four main criteria that will help you choose paper for routine as well as special projects.
Brightness refers to the percentage of light that is reflected back to the eye. A perfectly bright paper would be rated 100%.
Brightness varies according to paper category. For example, newsprint brightness usually ranges from 56 – 59. Optical brighteners such as fluorescents increase brightness. Bright sheets contrast with shaded areas and show the most clarity.
Gloss is an optical property of a surface to reflect light in a specular (mirror-like) direction. It is one of a number of important parameters that are used to describe the visual appearance of a printed piece. The factors that affect gloss are the refractive index of the material, the angle of incident light and the surface topography.
Opacity is the ability of paper to prevent show-through, which is measured as a percentage of the amount of light that passes through a sheet of paper. Most papers fall between 88 and 98 % opacity.
Caliper, filler and brightness all affect opacity.
- Thick paper is more opaque than thin.
- Rough paper is more opaque than smooth.
- Dark paper is more opaque than light.
The caliper of a paper will vary according to the basis weight and the finish of the paper. For example, a 30 lb. paper will be thicker than a 27 lb. paper for the same paper category, assuming the finish is the same for both. And a calendered paper will be thinner, since it has been squeezed between the calenders.
Book manufacturers tend to express the thickness of a paper in pages per inch (PPI). This is because papers of the same weight can have fairly dramatic differences in thickness. 50 lb. book papers, for example, can vary from 310 to 800 pages per inch, depending upon how it is made. Thickness can obviously affect a variety of important factors from the appearance of the final product to how many copies can fit into a truck or onto a display.
Basis Weight and M Weight
Don't feel bad if you find paper weights confusing, especially when you move from one grade to another – like bond to offset. The key point is that all paper is based on the weight of 500 sheets of paper (a ream) cut to a given standard size for that particular grade. The tricky part is that the standard size can change from grade to grade as well as with cover stocks. Here is more information and a guide to help you conquer the paper weight issue.
Adding further complexity to the weight issue is the introduction of foreign-manufactured papers that use the metric system to determine basis weight. In this system, it is the weight of one square meter of paper expressed as grams per square meter or g/m2. Basis 60# in the North American system means that 500 sheets 25" x 38" of 60 lb. book paper weigh 60 pounds. The metric equivalent of the same paper is 89 g/m2.
M weight is the weight for 1,000 sheets. For example, newsprint paper 60M means that 1,000 24" x 36" sheets weigh 60 lb.
To learn more about paper characteristics, contact us.