Card Modeling FAQ

Appendix: Glossary of Paper Terms

A4, A3, etc.
ISO standard paper sizes. See Markus Kuhn's excellent document International Standard Paper Sizes for a detailed description of the various ISO standard sizes, and EDS Incorporated's Guide to International Paper Sizes discusses Japanese standards.
Alkaline Paper
a non-acid paper with a high degree of permanence.
Basic Size
the standard size for a grade of paper, used to determine its basis weight; for example (in inches):
Bond - 17x22
Bristol - 22.5x28.5
Cover - 20x26
Dual Purpose - 17x22
Duplicator - 17x22
Index - 25.5x30.5
Ledger - 17x22
Lightweight Opaque - 25x38
Offset - 25x38
Safety - 17x22
Writing - 17x22
Also called basis size or parent size. The terms bond, cover, &c. are also called the paper's grade.
Basis Weight
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, 17x22 in., would weigh 20 lb.) See also: Substance.
Sometimes the same paper is assigned two basis weights, e.g. 24/60, meaning the same paper is sold in two different basis sizes. 24 lb. bond (basis size 17"x22") is approximately the same weight as 60 lb. text or offset (basis size 25"x38"). Note that basis weight is used mostly in North America. Outside North America, paper weight is usually specified in g/m². See also: gsm.
from Stephen Brown <>: The American measures of paper weights are nothing if not confusing. The weight (e.g. 80 pounds) of a paper refers to the weight of 500 sheets in the paper's basis size. The basis size varies with the type of paper. To convert to the more rational metric measure, you have to know both the weight and the basis size. Thus, for cover stock, the basis size is 20" by 26". A ream (500 sheets) is thus 500 x 520 square inches, or a total area of 260,000 square inches. Eighty pound cover stock is 80 lb per 260,000 square inches, or about 308 micropounds/square inch. One lb/square inch is about 704 kg/square meter; thus 80 pound cover stock is 216.5 gsm.

Twenty four pound bond or writing paper is measured with a basis size of 17" by 22", or 187,000 square inches per ream. Since the basis size is smaller than for cover stock, a sheet of bond paper would be heavier than a sheet of cover stock of the same nominal weight. 24 lb bond is about 90 gsm; 24 lb cover would be about 65 gsm. But cover stock isn't sold in a 24 lb weight, so in practice one rarely makes this sort of comparison. Wausau has a table for conversion of basis sizes.

It gets worse. The Wausau paper I've mentioned is sold as cover paper, but actually measured on a bristol basis, 22.5" by 28.5", or about 320,625 square inches per ream. The 67 lb bristol is thus 147 gsm, and is the weight equivalent of a 54 lb cover stock. It has a caliper (thickness in mils) of 8.4, approximately the same as Wilhelmshaven and JSC models, and very close to stuff I've seen identified as "65 lb cover stock". I'm beginning to suspect a certain sloppiness in distinguishing between cover stock and bristol stock in this country.

Caliper, of course, is an imperfect guide. Paper varies in density, so the same thickness can have differing weights. It has the virtue, however, of being easy to measure and compare.

Table showing equivalent weight in grams per square meter for various American paper weights and basis sizes. Note that not all the paper weights listed actually exist (e.g. cover stock is not sold in a 20 pound weight.)
Dual Purpose
Cover Bristol Index Offset
Basis size (inches)
17.0x22.0 20.0x26.0 22.5x28.5 25.5x30.5 25.0x38.0
20 75.3 gsm 54.1 gsm 43.9 gsm 36.2 gsm 29.6 gsm
24 90.3 gsm 65.0 gsm 52.7 gsm 43.4 gsm 35.6 gsm
28 105.4 gsm 75.8 gsm 61.5 gsm 50.7 gsm 41.5 gsm
60 225.8 gsm 162.4 gsm 131.7 gsm 108.6 gsm 88.9 gsm
67 252.1 gsm 181.3 gsm 147.1 gsm 121.2 gsm 99.3 gsm
80 301.0 gsm 216.5 gsm 175.6 gsm 144.8 gsm 118.5 gsm
110 413.9 gsm 297.7 gsm 241.4 gsm 199.1 gsm 163.0 gsm
Bond Paper
paper manufactured generally for stationery, letterheads or forms. Distinguishable in the more popular grades by a watermark and excellent writing surface.
the measurement of a paper's light-reflective qualities that affect contrast and halftone reproduction. A paper with 85% brightness reflects 85% of the light that strikes it. Brightness increases the contrast between the ink and the paper and makes a document easier to read. Brightness is only a factor in white papers.
thickness of the paper relative to its weight. High bulk paper is thicker than low bulk paper, but not heavier. (See also: Caliper.)
the process of running paper between polished steel rolls on the paper machine to produce a desired smoothness. Uncoated paper is calendered in this sequence from roughest to smoothest: Vellum, Antique, Wove, Smooth. (Note: Superior smoothness and gloss can also be accomplished off machine by supercalender equipment.)
the thickness of a sheet, or stack of sheets of paper as expressed in thousandths of an inch (mils); also referred to as Bulk.
Coated Paper
paper with a coated surface that gives the paper a smooth finish. (See also: Uncoated Papers.)
Cover Paper
a heavyweight paper designed particularly for covers of brochures and catalogs, business cards, posters, and similar applications.
generally paper that is 8 1/2x11 in., 8 1/2x14 in., or 11x17 in., or paper that does not exceed 16x21 in. in size.
identifies the weight of the paper compared to the thickness. Density is directly related to stiffness, absorbency, opacity, and resiliency.
Embossed Finish
a paper surface textured in one of a variety of patterns (e.g., Pearl, Linen, Ripple, etc.) by passing the paper through engraved steel rolls.
Felt Side
the "top" side of the paper as it is formed on the wire of the paper machine, and the side recommended for best printing results.
infinitesimally small particles of rag or wood pulp, which are the major raw ingredients in the papermaking process.
the special characteristics of a paper's surface, which differ from grade to grade. High, low and textured finishes, for example, exhibit varying degrees of smoothness, ink receptivity and printability.
Folio Size
paper that is 17x22 in. or larger.
the degree of uniformity with which fibers and other solids (fillers) are distributed in a sheet of paper. The more uniformity, the more level and smooth the sheet and the better the print quality.
the predominant alignment of fibers in the direction of the flow of stock during papermaking. (See also: Against the Grain, With the Grain.)
gsm or g/m²
grams per square meter.
Ink Holdout
the ability of the paper to keep ink on its surface rather than absorb it into the sheet (e.g., paper with good ink holdout would require less ink and exhibit less "feathering" than a highly absorbent paper).
Ink Receptivity
the degree to which a paper resists or accepts ink penetration based on variations in its size and coating.
Long-Grain Paper
paper in which the predominant fiber orientation parallels the longest sheet dimension. (See also: Short-Grain Paper.)
M Weight
the weight of 1,000 sheets of a grade of paper cut to its basic size; e.g., 17x22 in. Sub. 20 Bond is 40M. Sometimes this is the weight of 1,000 sheets of paper sold in sizes other than its basic size; e.g. 70 lb. text (basis size 25"x38") sold as a carton of 19"x25" sheets is said to have an M Weight of 70 lb.
Moisture Content
the percentage of moisture found in finished paper.
Offset Paper
an uncoated or coated paper, available in several finishes that incorporates characteristics specially suited for offset printing.
the amount of light that penetrates the paper and therefore the degree to which type shows through from the other side of the paper. Usually, the lower the basis weight, the less opacity.
Pages per inch. Divide 2 by the caliper to yield PPI. (Don't confuse pages per inch with sheets per inch; there are two pages, front and back, per sheet.)
500 sheets of paper, regardless of size. More specifically, a ream is 20 quires of paper. A quire is 24 or 25 sheets of paper, making a ream of paper 480 or 500 sheets. However, quire is an archaic unit; in modern usage, a ream is 500 sheets.
alignment of the printed area, so that two or more colors are accurately positioned with respect to each other on the sheet.
Short-Grain Paper
paper in which the predominant fiber orientation is parallel to the shortest sheet dimension. (See also: Long-Grain Paper.)
the surface characteristic relating to the flatness of a sheet, which affects ink receptivity.
quite simply, the paper.
weight in pounds of a ream of paper cut to its standard size (e.g., 500 sheets of 20 lb Bond in 17x22 in. size would be Substance 20). (See also: Basis Weight.)
Uncoated Paper
paper on which the printing surface is the paper itself and which may or may not be surface sized.
a paper manufacturer's name or faint design pressed into paper while it is still wet.
Wire Side
the "bottom" side of the sheet of paper, that is next to the wire when on the papermaking machine; opposite the "felt" or "top" side.
With the Grain
the position of the sheet that is parallel to the predominant orientation of the fibers. (See also: Grain, Against the Grain.)
Back to Card Modeling FAQ
Copyright © 1997-2002 by Steve Brown. Copyright notice

Mail | Steve Brown |