History
Early balls were made of various materials, including wood and clay (the latter remaining in use well into the 20th century). Although affordable ox-bone balls were in common use in Europe, elephant ivory was favored since at least 1627 until the early 20th century; the earliest known written reference to ivory billiard balls is in the 1588 inventory of the Duke of Norfolk. Dyed and numbered balls appeared around the early 1770s. By the mid-19th century, elephants were being slaughtered for their ivory at an alarming rate, just to keep up with the demand for high-end billiard balls – no more than eight balls could be made from a single elephant's tusks. The billiard industry realized that the supply of elephants (their primary source of ivory) was endangered, as well as dangerous to obtain (the latter an issue of notable public concern at the turn of the 19th century). Inventors were challenged to come up with an alternative material that could be manufactured, with a US$10,000 (worth approximately $ in ) prize being offered by a New York supplier. Although not the first artificial substance to be used for the balls (e.g.Types
Carom billiards
In the realm of carom billiards games, three balls are used to play most games on pocketless billiards tables. Carom balls are not numbered, and are 61–61.5 mm (approximately in) in diameter, and a weight ranging between with a typical weight of . Officially but somewhat poorly translated version, from the French original. They are typically colored as follows: * White: for player 1 * Yellow or white with a spot: cue ball for player 2 * Red (occasionally blue): ( four-ball uses an extra object ball.)Pool
Pool balls are used to play various pool games, such as eight-ball, nine-ball, and straight pool. These balls, the most widely used throughout the world, are smaller than carom billiards balls, and larger than those for snooker. According to World Pool-Billiard Association equipment specifications, the weight may be from with a diameter of , plus or minus . The balls are numbered and colored as in the table. Balls 1 through 7 are the of and 9 through 15 are the stripes . The 8 ball is not considered part of either suit. Striped balls were introduced around 1889. Rotation games do not distinguish between solids and stripes, but rather use the numbering on the balls to determine which must be pocketed. In other games such as straight pool neither type of marking is of any consequence. Some balls used in televised pool games are colored differently in order to make them more distinguishable on television monitors. Most commonly, the dark purple used on the 4 and 12 balls is replaced by pink to make it easier to distinguish the 4 from the black 8 ball, and similarly the 7 and 15 balls use a lighter brown color instead of a deep maroon. Other, less common color substitutions are also found, dependent on manufacturer. These sets often have a cue ball with multiple spots on its surface so that placed on it is evident to viewers. Coin-operated pool tables, such as those found at bowling alleys, arcades, or bars, may use a slightly different-sized cue ball, so that the cue ball can be separated from object balls by the table's ball return mechanism and delivered into its own ball return. Such different sized cue balls are considered less than ideal because they change the dynamics of the equipment. Other tables use a system where a magnet pulls a cue ball with a thin layer of metal embedded inside away from the object ball collection chamber and into the cue ball return, allowing the cue ball to more closely match the object balls in size and weight. More recently, optical systems that recognize the cue ball, which is more translucent than the other balls due to its solid white color, and separate it mechanically have been developed.Blackball pool
In blackball pool, fifteen object balls are used, but fall into two unnumbered , the (or less commonly ) and , with a white cue ball, and black 8 ball. Aside from the 8, shots are not since there is no reliable way to identify particular balls to be pocketed. Because they are unnumbered, they are wholly unsuited to certain pool games, such as nine-ball, in which ball order is important. They are typically smaller than the American-style balls; the most common object ball diameters are and . The yellow-and-red sets are sometimes referred to as "casino sets" as they were developed to make identification of suits easier for spectators at eight-ball championships often held in casinos. Such sets were sold by the Brunswick–Balke–Collender Co. as early as 1908. Similar to standard pool balls, there are also special sets designed for televised games; these sets have a black-striped 8 ball, and a spotted cue ball.Snooker
Ball sets for snooker consist of twenty-two balls in total, arranged as a rack of 15 unmarked red balls, six placed at various predetermined spots on the table, and a white cue ball. The colour balls are sometimes numbered with their point values in the style of pool balls for the home market. Snooker balls are standardized at in diameter within a tolerance of plus or minus . No standard weight is defined, but all balls in the set must be the same weight within a tolerance of ."Equipment"Other games
Various other games have their own variants of billiard balls. English billiards uses the same number of balls as carom billiards, but the same size as snooker balls, as the game is played on the same size table as snooker. Russian pyramid uses a set of fifteen numbered white balls and a red or yellow cue ball that are even larger than carom billiards balls at . Kaisa has the same pocket and ball dimensions but uses only five balls: one yellow, two red and two white cue balls, one for each player.Novelty balls
There is a market for specialty cue balls and even entire ball sets, featuring sports team logos, cartoon characters, animal pelt patterns, or other non-standard decorations. Entrepreneurial inventors also supply a variety of novelty billiard games with unique rules and balls, some with playing card markings, others with stars and stripes, and yet others in sets of more than thirty balls in several suits. Marbled-looking and glittery materials are also popular for home tables. There are even blacklight sets for playing in near-dark. There are also practical joke cue and 8 balls, with off-center weights in them that make their paths curve and wobble. Miniature sets in various sizes (typically or of normal size) are also commonly available, primarily intended for undersized toy tables. Even an egg-shaped ball has been patented and marketed under such names as Bobble Ball and Tag Ball.In popular culture
The 8 ball is frequently used in Western, especially American, culture as an element of T-shirt designs, album covers and names, tattoos, household goods like paperweights and cigarette lighters, belt buckles, etc. A classic toy is the Magic 8-Ball "oracle". The term "8-ball" is also slang both for of cocaine or crystal meth, and for a bottle of Olde English 800 malt liquor. It has also been used to refer to African-Americans, particularly those of darker skin tones, as in the film '' Full Metal Jacket''. The expression "behind the eightReferences
Patents
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