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 <cardfaq@bellsouth.net>: 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.)

Weight in Pounds	Bond Dual Purpose Duplicator Ledger Safety Writing	Cover	Bristol	Index	Offset Text Book
	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.

Brightness

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.

Bulk

thickness of the paper relative to its weight. High bulk paper is thicker than low bulk paper, but not heavier. (See also: Caliper.)

Calendering

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.)

Caliper

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.

Cut-Size

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.

Density

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.

Fibers

infinitesimally small particles of rag or wood pulp, which are the major raw ingredients in the papermaking process.

Finish

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.

Formation

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.

Grain

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.

Opacity

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.

PPI

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.)

Ream

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.

Registration

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.)

Smoothness

the surface characteristic relating to the flatness of a sheet, which affects ink receptivity.

Stock

quite simply, the paper.

Substance

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.

Watermark

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.)

• Hammermill Papers.
• Paperplace USA.
• Wausau Papers.
• Weyerhaeuser.