Grammage and basis weight, in the pulp and paper industry, are the area density of a paper product, that is, its mass per unit of area. Two ways of expressing grammage are commonly used:
In the metric system, the mass per unit area of all types of paper and paperboard is expressed in terms of grams per square metre (g/m2 or gsm). This quantity is commonly called grammage in both English and French, [2] though printers in most English-speaking countries still refer to the "weight" of paper.
Typical office paper has 80 g/m2 (0.26 oz/sq ft), therefore a typical A4 sheet (1⁄16 of a square metre) weighs 5 g (0.18 oz). The abbreviation "gsm" instead of the standard "g/m2" symbol is also widely encountered in English-speaking countries.
Typically grammage is measured in paper mill on-line by a quality control system and verified by laboratory measurement.
In countries that use American paper sizes, a less verifiable measure known as basis weight is used in addition to or instead of grammage. The basis weight of paper is the density of paper expressed in terms of the mass of a ream of given dimensions and a sheet count. In the US system, the weight is specified in avoirdupois pounds and the sheet count of a paper ream is usually 500 sheets. However, the mass specified is not the mass of the ream that is sold to the customer. Instead, it is the mass of the uncut "basis ream" in which the sheets have some larger size (parent size). Often, that is a size used during the manufacturing process before the paper is cut to the dimensions in which it is sold. So, to compute the mass per area, one must know
The standard dimensions and sheet count of a ream vary according to the type of paper. These "uncut" basis sizes are not normally labelled on the product, are not formally standardized, and therefore have to be guessed or inferred somehow from trading practice. Historically, this convention is the product of pragmatic considerations such as the size of a sheet mold.
By using the same basis sheet size for the same type of paper, consumers can easily compare papers of differing brands. Twenty-pound bond paper is always lighter and thinner than 32-pound bond, no matter what its cut size, and 20-pound bond letter size and 20-pound bond legal size papers are the same weight paper with a different cut size.
However, a sheet of common copy paper that has a basis weight of 20 pounds (9.1 kg) does not have the same mass as the same size sheet of coarse paper (newsprint). In the former case, the standard ream is 500 sheets of 17-by-22-inch (432 by 559 mm) paper, and in the latter, 500 sheets of 24-by-36-inch (610 by 914 mm) paper. Here are some basic ream sizes for various types of paper. Units are inches except where noted.
Paper type | Paper size (inches) | Sheets per ream | |
---|---|---|---|
Bond, writing, ledger | 17 | × 22 | 500 |
Manuscript cover | 18 | × 31 | 500 |
Blotting | 19 | × 24 | 500 |
Box cover | 20 | × 24 | 500 |
Cover | 20 | × 26 | 500 or 1000 |
Watercolor | 22 | × 30 | 500 |
Bristol and tag | 22+1⁄2 | × 28+1⁄2 | 500 |
Tissue | 24 | × 36 | 480 |
Newsprint | 24 | × 36 | 500 |
Hanging, waxing, bag, etc. | 24 | × 36 | 500 |
Book, text, offset | 25 | × 38 | 500 |
Index bristol | 25+1⁄2 | × 30+1⁄2 | 500 |
Paperboard (all types) | 12 | × 12 | 1000 (1000 sq ft per ream) |
Sheets 17 by 22 inches (432 by 559 mm) can be cut into four 8+1⁄2-by-11-inch (216 by 279 mm) sheets, a standard for business stationery known conventionally as letter sized paper. So, the 17-by-22-inch (432 by 559 mm) ream became commonly used. The 25-by-38-inch (635 by 965 mm) book-paper ream developed because such a size can easily be cut into sixteen 6-by-9-inch (152 by 229 mm) book sized sheets without significant waste (nominally 6+1⁄4-by-9+1⁄2-inch (159 by 241 mm) before trimming and binding).
Early newsprint presses printed sheets 2 by 3 feet (610 by 914 mm) in size, and so the ream dimensions for newsprint became 24 by 36 inches (610 by 914 mm), with 500 sheets to a ream. Newsprint was made from ground wood pulp, and ground wood hanging paper (wallpaper) was made on newsprint machines. Newsprint was used as wrapping paper, and the first paper bags were made from newsprint. The newsprint ream standard also became the standard for packaging papers, even though in packaging papers kraft pulp, rather than ground wood, was used for greater strength.
Paper weight is sometimes stated using the "#" symbol. For example, "20#" means "20 pounds per basis ream of that kind of paper". When the density of a ream of paper is given in pounds, it is often accompanied by its "M weight" (M is 1000 in Roman numerals). The M weight is the weight (in pounds) of 1000 cut sheets. Paper suppliers will often charge by M weight, since it is always consistent within a specific paper size, and because it allows a simple weight calculation for shipping charges.
For example, a 500-sheet ream of 20# 8+1⁄2-by-11-inch (216 by 279 mm) copy paper may be specified "10 M". 1000 cut sheets (or two reams) will weigh 10 lb (4.5 kg), half of the four reams of cut paper resulting from the 20# basis ream of 17-by-22-inch (432 by 559 mm) paper.
Paper thickness, or caliper, is a common measurement specified and required for certain printing applications. Since a paper's density is typically not directly known or specified, the thickness of any sheet of paper cannot be calculated by any method. Instead, it is measured and specified separately as its caliper. However, paper thickness for most typical business papers might be similar across comparable brands. If thickness is not specified for a paper in question, it must be either measured or guessed based on a comparable paper's specification.
Caliper is usually measured in micrometres (μm), or in the United States also in mils (1 mil = 1⁄1000 in = 25.4 μm). Commonly, 20-pound bond paper ranges between roughly 97 and 114 μm (0.0038 and 0.0045 in) in thickness. [3]
The paper density is calculated by dividing the grammage over the caliper, and is usually expressed in grams per cubic centimetre (g/cm3) [4] to cancel out the mathematical need for unit conversions between metres and micrometres (a conversion factor of 1,000,000).[ citation needed ]
ISO 216 is an international standard for paper sizes, used around the world except in North America and parts of Latin America. The standard defines the "A", "B" and "C" series of paper sizes, which includes the A4, the most commonly available paper size worldwide. Two supplementary standards, ISO 217 and ISO 269, define related paper sizes; the ISO 269 "C" series is commonly listed alongside the A and B sizes.
United States customary units form a system of measurement units commonly used in the United States and most U.S. territories, since being standardized and adopted in 1832. The United States customary system developed from English units that were in use in the British Empire before the U.S. became an independent country. The United Kingdom's system of measures was overhauled in 1824 to create the imperial system, which was officially adopted in 1826, changing the definitions of some of its units. Consequently, while many U.S. units are essentially similar to their imperial counterparts, there are noticeable differences between the systems.
Lumber is wood that has been processed into uniform and useful sizes, including beams and planks or boards. Lumber is mainly used for construction framing, as well as finishing. Lumber has many uses beyond home building. Lumber is referred to as timber in the United Kingdom, Europe, Australia, and New Zealand, while in other parts of the world the term timber refers specifically to unprocessed wood fiber, such as cut logs or standing trees that have yet to be cut.
Corrugated fiberboard, corrugated cardboard, or corrugated is a type of packaging material consisting of a fluted corrugated sheet and one or two flat linerboards. It is made on "flute lamination machines" or "corrugators" and is used for making corrugated boxes. The corrugated medium sheet and the linerboard(s) are made of kraft containerboard, a paperboard material usually over 0.25 millimetres (0.01 in) thick.
Paper size standards govern the size of sheets of paper used as writing paper, stationery, cards, and for some printed documents.
In guns, particularly firearms, but not artillery, where a different definition may apply, caliber is the specified nominal internal diameter of the gun barrel bore – regardless of how or where the bore is measured and whether the finished bore matches that specification. It is measured in inches or in millimeters. In the United States it is expressed in hundredths of an inch; in the United Kingdom in thousandths; and elsewhere in millimeters. For example, a US "45 caliber" firearm has a barrel diameter of roughly 0.45 inches (11.43mm). Barrel diameters can also be expressed using metric dimensions. For example, a "9 mm pistol" has a barrel diameter of about 9 millimeters. Since metric and US customary units do not convert evenly at this scale, metric conversions of caliber measured in decimal inches are typically approximations of the precise specifications in non-metric units, and vice versa.
Paperboard is a thick paper-based material. While there is no rigid differentiation between paper and paperboard, paperboard is generally thicker than paper and has certain superior attributes such as foldability and rigidity. According to ISO standards, paperboard is a paper with a grammage above 250 g/m2, but there are exceptions. Paperboard can be single- or multi-ply.
The area density of a two-dimensional object is calculated as the mass per unit area. The SI derived unit is the kilogram per square metre (kg·m−2). A related area number density can be defined by replacing mass in by number of particles or other countable quantity.
Letter is a paper size standard defined in ANSI/ASME Y14.1 by the American National Standards Institute, commonly used as home or office stationery primarily in the United States, Canada, and the Philippines, and variably across Latin America. It measures 8.5 by 11 inches and is similar in use to the A4 paper standard at 210 mm × 297 mm used by most other countries, defined in ISO 216 by the International Organization for Standardization.
The gauge of a firearm is a unit of measurement used to express the inner diameter of the barrel.
Bristol board is an uncoated, machine-finished paperboard.
Wire gauge is a measurement of wire diameter. This determines the amount of electric current the wire can safely carry, as well as its electrical resistance and weight.
Paper density is a paper product's mass per unit volume. The density can be calculated by dividing the grammage of paper by its caliper.
Textile fibers, threads, yarns and fabrics are measured in a multiplicity of units.
Card stock, also called cover stock and pasteboard, is paper that is thicker and more durable than normal writing and printing paper, but thinner and more flexible than other forms of paperboard.
Various measures of paper quantity have been and are in use. Although there are no S.I. units such as quires or bales, there are ISO and DIN standards for the ream. Expressions used here include U.S. Customary Units.
A book paper is a paper that is designed specifically for the publication of printed books.
Paper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, rags, grasses, or other vegetable sources in water, draining the water through a fine mesh leaving the fibre evenly distributed on the surface, followed by pressing and drying. Although paper was originally made in single sheets by hand, almost all is now made on large machines—some making reels 10 metres wide, running at 2,000 metres per minute and up to 600,000 tonnes a year. It is a versatile material with many uses, including printing, painting, graphics, signage, design, packaging, decorating, writing, and cleaning. It may also be used as filter paper, wallpaper, book endpaper, conservation paper, laminated worktops, toilet tissue, currency, and security paper, or in a number of industrial and construction processes.
A variety of tests are used to determine ink and paper and paperboard quality, and to measure their interactions. They are necessary to balance print quality, cost, and wear on the press. Some of the important paper and ink tests are listed here:
Paperweight is a small solid object which is placed on top of books to keep the papers from blowing in the breeze or to keep a sheet from moving when painting with a brush as with Japanese calligraphy