In 1869, John Wesley Hyatt invented a composition material called cellulose nitrate for billiard balls (US patent 50359, the first American patent for billiard balls). It is unclear if the cash prize was ever awarded to Hyatt, and there is no evidence suggesting he did in fact win it By 1870 it was commercially branded Celluloid, the first industrial plastic. Unfortunately, the nature of celluloid made it volatile in production, occasionally exploding, which ultimately made this early plastic impractical.
Subsequently, to avoid the problem of celluloid instability, the industry experimented with various other synthetic materials for billiards balls such as Bakelite, Crystalate and other plastic compounds.
The exacting requirements of the billiard ball are met today with balls cast from plastic materials that are strongly resistant to cracking and chipping. Currently Saluc, under the brand names Aramith and Brunswick Centennial, manufactures phenolic resin balls. Other plastics and resins such as polyester (under various trade names) and clear acrylic are also used, by competing companies such as Elephant Balls Ltd., Frenzy Sports, and Vigma
In the realm of carom (or carambole) games, billiard balls are the three (sometimes four) balls used to play straight-rail, three-cushion, balkline, and related games on pocketless billiards tables, as well as English billiards which is played on a table with pockets. The predominantly-Asian game four-ball uses four balls (the name literally means "four-balls"). Carom balls are not numbered, and at inches (61.5 mm) are larger than pool balls. They are colored as follows:
In the US, the term "billiard balls" usually (except among carom players) refers to balls used to play various pocket billiards (pool) games, such as eight-ball, nine-ball and one-pocket; they are commonly referred to as kelly pool or American balls in the UK. These pool balls, used the most widely throughout the world, are considerably smaller than carom billiards balls, slightly larger than British-style pool balls and substantially larger than those for snooker. According to BCA/WPA equipment specifications, the weight may be from 5.5 to 6 oz. (156 to 170 g) with a diameter of 2.25 in. (5.715 cm), plus or minus 0.005 in. (0.127 mm).. The balls are numbered and colored as follows:
Note that balls 1–7 are often referred to as and 9–15 as though there are many other colloquial terms for each of balls. Though it looks similar to the solids, the 8 ball is not considered a solid. Some games such as nine-ball do not distinguish between stripes and solids, but rather use the numbering on the balls to determine which object ball must be pocketed, in other games such as three-ball neither type of marking is of any consequence. In eight-ball, straight pool, and related games, all sixteen balls are employed. In the game of nine-ball, only object balls 1 through 9 (plus the cue ball) are used. Some balls used in televised pool games are colored differently to make them distinguishable on television monitors (thus the pink and tan variants). TV is also the genesis of the "measle" cue ball with numerous spots on its surface so that spin placed on it is evident to viewers.
Coin-operated pool tables such as those found at bars and college campuses historically have often used either a larger ("grapefruit") or denser ("rock", typically ceramic) cue ball, such that its extra weight makes it easy for the cue ball return mechanism to separate it from object balls (which are captured until the game ends and the table is paid again for another game) so that the cue ball can be returned for further play, should it be accidentally pocketed. Rarely in the US, some pool tables use a smaller cue ball instead. Modern tables usually employ a magnetic ball of regulation or near-regulation size and weight, since players have rightly complained for many decades that the heavy and often over-sized cue balls do not "play" correctly.
In WPA blackball and WEPF or English-style eight-ball pool (not to be confused with the games of eight-ball of English billiards), fifteen balls again are used, but are arrayed in 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 noticeably smaller than the American-style balls, and with a cue ball that is slightly smaller than the object balls, while the table's are tighter to compensate. Neither the WPA nor the WEPF (publicly) define ball or even table dimensions, though presumably league and tournament organizers are given some guidelines in this regard. Most manufacturers that supply this market provide 2 in. (5.08 cm) object balls and inches (4.76 cm) cue balls. The yellow-and-red sets are sometimes commercially referred to as "casino sets" (they were formerly used for televised eight-ball championships – most often held in casinos). The use of such sets, however, pre-dates television, as they were used for B.B.C. Co. Pool, the forerunner of modern eight-ball, at least as early as 1908.
Ball sets for the sport of snooker look at first glance like a mixture of American- and British-style pool balls. There are twenty-two balls in total, arranged as a rack of fifteen unmarked reds, six placed at various predetermined spots on the table, and a white cue ball. (See snooker for more information on ball setup.) The colour balls are sometimes numbered American-style, with their point values, for the amateur/home market. They are numbered as follows:
Various other games have their own variants of billiard balls. Russian pyramid and the related Finnish game kaisa make use of a set of 15 numbered but otherwise all-white balls, and a red or yellow cue ball, that may be even larger than carom billiards balls, at 68 mm (211⁄16 in) or 72 mm (24⁄5 in).. Bumper pool requires four white and four red object balls, and two special balls, one red with a white spot and the other the opposite; all are usually inch (approximately 52.5 mm) in diameter.
Several brands of practice balls exist, which have systems of spots, stripes, differently-colored halves and/or targeting rings.
For example, Saluc markets several practice ball systems, including the Jim Rempe Training Ball, a marked with rings and targets on the surface of the ball so that the practicing player can better judge the effects of very particular amounts of , , and other forms of cue ball control, and learn better control of cue . Various competing products, such as several other Saluc models and Elephant Practice Balls, use a similar aiming system. Some such sets consist of just a special cue ball and manual, while others contain both a cue ball and an object ball marked for aiming practice, along with the documenation.
There is a growing market for specialty cue balls and even entire ball sets, featuring sports team logos, cartoon characters, animal pelt patterns, etc. 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 under-sized toy tables.