A football is an inflated ball used to play one of the various sports known as football. In these games, with some exceptions, goals or points are scored only when the ball enters one of two designated goal-scoring areas; football games involve the two teams each trying to move the ball in opposite directions along the field of play. A football is generally a tool of the offense.
The first balls were made of natural materials, such as an inflated pig bladder, later put inside a leather cover, which has given rise to the United States slang-term "pigskin". Modern balls are designed by teams of engineers to exacting specifications, with rubber or plastic bladders, and often with plastic covers. Various leagues and games use different balls, though they all have one of the following basic shapes:
- a sphere: used in Association football and Gaelic football
- a prolate spheroid
The precise shape and construction of footballs is typically specified as part of the rules and regulations.
The oldest football still in existence, which is thought to have been made circa 1540, was discovered in the roof of Stirling Castle, Scotland, in 1981. The ball is made of leather (possibly from a deer) and a pig's bladder. It has a diameter of between 14–16 cm (5.5–6.3 in), weighs 125 g (4.4 oz) and is currently on display at the Smith Art Gallery and Museum in Stirling.
American and Canadian football
In Canada and the United States, the term football usually refers to a ball made of leather, which is required in professional and collegiate football. Footballs used in recreation, and in organised youth leagues, may be made of rubber or plastic materials (the high school football rulebooks still allow the inexpensive all-rubber footballs, though they are less common than leather).
Leather panels are usually tanned to a natural brown color, which is usually required in professional leagues and collegiate play. At least one manufacturer uses leather that has been tanned to provide a "tacky" grip in dry or wet conditions. Historically, white footballs have been used in games played at night so that the ball can be seen more easily; however, this practice is no longer commonplace, as artificial lighting conditions have improved to the point where it is no longer necessary. Two indoor American football leagues, the Ultimate Indoor Football League and American Indoor Football, use a ball with red, white and blue panels. At most levels of play (but not, notably, the NFL), white stripes are painted on each end of the ball, halfway around the circumference, to improve nighttime visibility. The UFL used a ball with lime-green stripes. In the CFL the stripes traverse the entire circumference of the ball. The XFL used a novel color pattern, a black ball with red curved lines in lieu of stripes, for its footballs; this design was redone in a tan and navy color scheme for the Arena Football League in 2003.
The leather is usually stamped with a pebble-grain texture to help players grip the ball. Some or all of the panels may be stamped with the manufacturer's name, league or conference logos, signatures, and other markings.
Two of the panels are perforated along adjoining edges, so that they can be laced together. One of these lacing panels receives an additional perforation and reinforcements in its center, to hold the inflation valve.
Each panel is attached to an interior lining. The four panels are then stitched together in an "inside-out" manner. The edges with the lacing holes, however, are not stitched together. The ball is then turned right side out by pushing the panels through the lacing hole.
A polyurethane or rubber lining called a bladder is then inserted through the lacing hole.
Polyvinyl chloride or leather laces are inserted through the perforations, to provide a grip for holding, hiking and passing the football.
Before play, the ball is inflated to an air pressure of 12.5 to 13.5 pounds per square inch (86 to 93 kilopascals). The ball weighs 14 to 15 ounces (400 to 430 grams).
In an NFL game, the home club must have 36 balls for an outdoor game or 24 for an indoor game, and they must be available for the referee to test with a pressure gauge two hours before the game. Twelve new footballs, sealed in a special box and shipped by the manufacturer, are opened in the officials’ locker room two hours before the game. These balls are specially marked with the letter "K" and used exclusively for the kicking game.
Since 1941, Horween Leather Company has been the exclusive supplier of leather for National Football League footballs. The arrangement was established initially by Arnold Horween, who had played and coached in the NFL. During that time, he met and played against George Halas, an NFL player and later coach and owner of the Chicago Bears, with whom he became friends. Halas' connection with the Wilson sporting goods company and the NFL led to Horween Leather Company supplying the leather with NFL footballs. The company uses its own "Tanned in Tack" process. Although footballs are often called "pigskins," they are made from Horween Leather Company-supplied steer hides that are embossed with a pebble pattern. Horween Leather Company also supplies leather to Spalding (a division of Russell Corporation) for indoor Arena Football League footballs.
Law 2 of the game specifies that the ball is an air-filled sphere with a circumference of 68–70 cm (27–28 in), a weight of 410–450 g (14–16 oz), inflated to a pressure of 0.6 to 1.1 atmospheres (60–111 kPa or 8.7–16.1 psi) "at sea level", and covered in leather or "other suitable material". The weight specified for a ball is the dry weight, as older balls often became significantly heavier in the course of a match played in wet weather. The standard ball is a Size 5, although smaller sizes exist: Size 3 is standard for team handball and Size 4 in futsal and other small-field variants. Other sizes are used in underage games or as novelty items.
Most modern footballs are stitched from 32 panels of waterproofed leather or plastic: 12 regular pentagons and 20 regular hexagons. The 32-panel configuration is the spherical polyhedron corresponding to the truncated icosahedron; it is spherical because the faces bulge from the pressure of the air inside. The first 32-panel ball was marketed by Select in the 1950s in Denmark. This configuration became common throughout Continental Europe in the 1960s, and was publicised worldwide by the Adidas Telstar, the official ball of the 1970 World Cup.
There are a number of different types of football balls depending on the match and turf including: training soccer balls, match soccer balls, professional match soccer balls, beach soccer balls, street soccer balls, indoor soccer balls, turf balls, futsal soccer balls and mini/skills soccer balls. 
Australian rules football
The football used in Australian football is similar to a rugby ball but generally slightly smaller and more rounded at the ends, but more elongated in overall appearance, being longer by comparison with its width than a rugby ball. A regulation football is 720–730 millimetres (28–29 in) in circumference, and 545–555 mm (21.5–21.9 in) transverse circumference, and inflated to a pressure of 62–76 kPa (9.0–11.0 psi). In the AFL, the balls are red for day matches and yellow for night matches.
The first games of Australian football were played with a round ball, because balls of that shape were more readily available. In 1860, Australian football pioneer Tom Wills argued that the oval rugby ball travelled further in the air and made for a more exciting game. It became customary in Australian football by the 1870s.
The Australian football ball was invented by T. W. Sherrin in 1880, after he was given a misshapen rugby ball to fix. Sherrin designed the ball with indented rather than pointy ends to give the ball a better bounce.
Gaelic football is played with a spherical leather ball, roughly 25 cm (10 in) in diameter and 69–74 cm (27–29 in) in circumference. A dry ball weighs between 370 and 425 g (13 and 15.0 oz). The pattern of panels is identical to the volleyball, consisting of six groups perpendicular to each other, each group being composed of two trapezoidal panels and one rectangular panel; 18 panels in all.
Gaelic footballs are also the standard balls used in international rules football.
Although Gaelic football has been played with a round ball since first organised in 1887, balls made by the Irish sports company O'Neills have been used sometime since the company was founded in 1918 and are recognised as the official ball to be played with, although it is now permitted to use the Gaelic ball manufactured by the Irish sports company Gaelic Gear.
Richard Lindon and Bernardo Solano started making balls for Rugby school out of hand stitched, four-panel, leather casings and pigs’ bladders. The rugby ball's distinctive shape is supposedly due to the pig’s bladder, although early balls were more plumb-shape than oval. The balls varied in size in the beginning depending upon how large the pig’s bladder was.
Until 1870, rugby was played with a near spherical ball with an inner-tube made of a pig's bladder. In 1870 Richard Lindon introduced rubber inner-tubes and because of the pliability of rubber the shape gradually changed from a sphere to an egg. In 1892 the RFU endorsed ovalness as the compulsory shape. The gradual flattening of the ball continued over the years. The introduction of synthetic footballs over the traditional leather balls, in both rugby codes, was originally governed by weather conditions. If the playing surface was wet, the synthetic ball was used, because it wouldn't absorb water and become heavy. Eventually, the leather balls were phased out completely.
Rugby league is played with a prolate spheroid shaped football which is inflated with air. A referee will stop play immediately if the ball does not meet the requirements of size and shape. Traditionally made of brown leather, modern footballs are synthetic and manufactured in a variety of colours and patterns. Senior competitions should use light coloured balls to allow spectators to see the ball more easily. The football used in rugby league is known as "international size" or "size 5" and is approximately 27 cm (11 in) long and 60 cm (24 in) in circumference at its widest point. Smaller-sized balls are used for junior versions of the game, such as "Mini" and "Mod". A full size ball weighs between 383 and 440 g (13.5 and 16 oz). Rugby league footballs are slightly more pointed than rugby union footballs and larger than American footballs.
The ball used in rugby union, usually referred to as a rugby ball, is a prolate spheroid essentially elliptical in profile. Traditionally made of brown leather, modern footballs are manufactured in a variety of colors and patterns. A regulation football is 28–30 cm (11–12 in) long and 58–62 cm (23–24 in) in circumference at its widest point. It weighs 410–460 g (14–16 oz) and is inflated to 65.7–68.8 kPa (9.5–10.0 psi).
In 1980, leather-encased balls, which were prone to water-logging, were replaced with balls encased in synthetic waterproof materials. The Gilbert Synergie was the match ball of the 2007 Rugby World Cup.
- "Scottish Cup – World's Oldest Football". Homecoming Scotland 2009. Retrieved 30 May 2011.
- "Oldest football to take cup trip". BBC News. 25 April 2006. Retrieved 2 May 2010.
- "Collections – Stirling Smith Art Gallery and Museum". Smithartgallery.demon.co.uk. Retrieved 30 May 2011.
- Cochems, Eddie, "The Forward Pass and On-Side Kick", Spalding's How to Play Foot Ball, American Sports Publishing, Walter Camp, Editor, Revised 1907 edition
- "Rulebook". Nfl.com. Retrieved 30 May 2011.
- "The NFL’s centenarians". Profootballhof.com. February 7, 2010. Retrieved March 27, 2013.
- Scott Oldham (October 2001). Bombs Away. Popular Mechanics. Retrieved March 26, 2013.
- John Maxymuk (2012). NFL Head Coaches: A Biographical Dictionary, 1920–2011. McFarland. Retrieved March 26, 2013.
- Barbara Rolek (October 27, 2003). "Horween's leather bound by tradition". Chicago Tribune. Retrieved March 27, 2013.
- Howard Wolinksy (May 16, 2008). Horween Leather Faces an Uncertain Future. Business Week. Retrieved March 26, 2013.
- "'Pigskin' They're Kicking is Cow". Chicago Tribune. September 30, 1954. Retrieved March 27, 2013.
- Horween Leather Company. encyclopedia.com. Retrieved March 26, 2013.
- "Laws of the Game". FIFA. Retrieved 30 May 2011.
- Soccer Balls, Soccer, 2013-10-14. Retrieved: 2013-10-14.
- Flanagan, Martin. "Why Tom Wills is an Australian legend like Ned Kelly", Australian Football. Retrieved 7 November 2013.
- "International Australian Football Council". Web.archive.org. 23 August 2006. Retrieved 30 May 2011.
- "Official Website:: SalthillKnocknacarraGaa.ie". Web.archive.org. 3 May 2008. Retrieved 30 May 2011.
- Simon Hawkesley. Official Richard Lindon Site. Retrieved 7 August 2008.
- Blood, mud and aftershave in The Observer Sunday February 5, 2006, Section B is for Ball by Oliver Price
- RLIF (2004). "Section 3: The ball". The International Laws of the Game and Notes on the Laws. Rugby League International Federation. p. 8. Retrieved 30 July 2008.
- "Rugby Union: Law 2 – The ball". Web.archive.org. 15 January 2007. Retrieved 30 May 2011.
- Angela Royston, 2005. How Is a Soccer Ball Made? Heinemann. ISBN 1-4034-6642-4.
- FIFA Quality Concept for Footballs
- Antique association football balls
- Construction of Soccer Balls
- club soccer balls Website
- Correct football care
- Ki-o-Rahi history and rules
- Official FIFA Football BALL Website
- More About WC Balls & Finals
- Paper model truncated icosahedron (association football ball)
- Popular Mechanics article on American football manufacturing process
- Soccer Ball World