A tennis ball is a ball designed for the sport of tennis. Tennis balls are yellow at major sporting events, but in recreational play can be virtually any color. Tennis balls are covered in a fibrous felt which modifies their aerodynamic properties, and each has a white curvilinear oval covering it.
Before the development of lawn tennis in the early 1870s, the sport was played as the courtly game of real tennis. England banned the importation of tennis balls, playing cards, dice, and other goods in the Act of Parliament Exportation, Importation, Apparel Act 1463. In 1480, Louis XI of France forbade the filling of tennis balls with chalk, sand, sawdust, or earth, and stated that they were to be made of good leather, well-stuffed with wool. Other early tennis balls were made by Scottish craftsmen from a wool-wrapped stomach of a sheep or goat and tied with rope. Those recovered from the hammer-beam roof of Westminster Hall during a period of restoration in the 1920s were found to have been manufactured from a combination of putty and human hair, and were dated to the reign of Henry VIII. Other versions, using materials such as animal fur, rope made from animal intestines and muscles, and pine wood, were found in Scottish castles dating back to the 16th century. In the 18th century, 3⁄4 in (1.9 cm) strips of wool were wound tightly around a nucleus made by rolling a number of strips into a little ball. String was then tied in many directions around the ball and a white cloth covering sewn around the ball.
In the early 1870s lawn tennis arose in Britain through the pioneering efforts of Walter Clopton Wingfield and Harry Gem, often using Victorian lawns laid out for croquet. Wingfield marketed tennis sets, which included rubber balls imported from Germany. After Charles Goodyear invented vulcanised rubber, the Germans had been most successful in developing vulcanised air-filled rubber balls. These were light and coloured grey or red with no covering. John Moyer Heathcote suggested and tried the experiment of covering the rubber ball with flannel, and by 1882 Wingfield was advertising his balls as clad in stout cloth made in Melton Mowbray.
Tennis balls must conform to certain criteria for size, weight, deformation, and bounce criteria to be approved for regulation play. The International Tennis Federation (ITF) defines the official diameter as 6.54–6.86 cm (2.57–2.70 inches). Balls must have masses in the range 56.0–59.4 g (1.98–2.10 ounces). Yellow and white are the only colors approved by the United States Tennis Association (USTA) and ITF, and most balls produced are fluorescent yellow (known as "optic yellow") the color first being introduced in 1972 following research demonstrating they were more visible on (color) television. The man credited with introducing the yellow ball in a tournament is Mike Davies. Tennis balls are filled with air and are surfaced by a uniform felt-covered rubber compound, although some manufacturers have produced balls filled with small polystyrene balls. The felt delays flow separation in the boundary layer which reduces aerodynamic drag and gives the ball better flight properties. Often the balls will have a number on them in addition to the brand name. This helps distinguish one set of balls from another of the same brand on an adjacent court.
Tennis balls begin to lose their bounce as soon as the tennis ball can is opened and can be tested to determine their bounce. A ball is tested for bounce by dropping it from a height of 254 cm (100 inches) onto concrete; a bounce between 135 and 147 cm (53 and 58 inches) is acceptable—if taking place at sea-level and 20 °C (68 °F) with relative humidity of 60%; high-altitude balls have different characteristics when tested at sea-level. Modern regulation tennis balls are kept under pressure (approximately two atmospheres) until initially used.
Pressureless balls vs Pressurized Balls
Traditional pressureless balls usually have a stiffer, woodier feel than pressurized balls and do not bounce as high as brand new pressurized balls. Unlike pressurized balls, though, they do not lose bounce over time. In fact, they get bouncier as they get lighter, due to fuzz loss. The balder they get, the more their flight, bounce, and spin responses change from what you would expect of tennis balls.
More advanced pressureless balls are more similar to the feel and play of pressurized balls, and last many times longer than traditional tennis balls.
Pressurized balls come in a pressurized can; once the can is popped open and the balls are exposed to the surrounding air, and the internal pressure (playability) starts to slowly diminish. Pressurized balls generally have more of a live feel (a nice bounce), more spin response, and travels faster pressureless balls. The only downside to pressurized balls are that they have a very short life span compared to pressureless balls. Cans of pressurized tennis balls are usually sold at 3 balls a can, and are used for matches.
Before 1925, tennis balls were packaged in wrapped paper and paperboard boxes. In 1925, Wilson-Western Sporting Goods Company introduced cardboard tubes. In 1926, the Pennsylvania Rubber Company released a hermetically sealed pressurized metal tube that held three balls with a churchkey to open the top. Beginning in the 1980s, plastic (from recycled PET) cans with a full-top pull-tab seal and plastic lid fit three or four balls per can. Pressureless balls tend to come in nets or bags (since they do not need to be pressure-sealed).
Each year approximately 300 million balls are produced, which contributes roughly 20,000 tonnes (22,000 tons) of waste in the form of rubber that is not easily biodegradable. Historically, tennis ball recycling has not existed. Balls from The Championships, Wimbledon are now recycled to provide field homes for the nationally threatened Eurasian harvest mouse. Tennis balls can also be rejuvenated or recycled using commercial services from reBounces. The BNP Paribas Open partnered with reBounces from 2009 through 2012 to collect 250,000+ tennis balls from tournament patrons from over 35 U.S. states and six countries.
The ITF Play and Stay campaign aims to increase tennis participation worldwide, by improving the way starter players are introduced to the game. The campaign promotes the use of slower red, orange and green balls that give players more time and control so that they can serve, rally, and score (play the game) from the first lesson.
By using slower balls the starter players have more time and more control to make the game more fun for them at the introductory stage. The ITF Intro to Tennis Task Force recommends the red, orange, green progression for starter players. This progression focuses on a range of slower balls and court sizes to introduce the game effectively to both adults and children.
Using these slower balls will help the players to develop the most efficient technique and to be able to implement tactical situations in matches that, in most cases, could not be performed using the normal ball on a full court.
The ITF recommends that, except for exceptional players, all players aged 10 and under should use a slower red, orange or green ball in training and competition.
Tennis balls in Literature
The gift of tennis balls offered to Henry in Shakespeare's Henry V is portrayed as the final insult which re-ignites the Hundred Years' War between England and France.
'When we have match'd our rackets to these balls, We will, in France, by God's grace, play a set' 
John Webster also refers to tennis balls in The Duchess of Malfi
'We are merely the stars' tennis balls, struck and banded Which way please them' 
- "U.S. Open Tennis Ball F.A.Q.".
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- "ITF tennis – TECHNICAL". itftennis.com. International Tennis Federation. Retrieved 12 September 2014.
- Recycling, PETRA (PET Resin Association), retrieved 21 July 2010
- "New balls, please" for mice homes
- BNP Paribas Sponsors Tennis Ball Recycling Program with reBounces
- Henry v, act 1, scene 2
- The Duchess of Malfi, act 5, scene 4
|Wikimedia Commons has media related to Tennis balls.|
- International Tennis Federation's history of the rules of the tennis ball
- ITF Grand Slam Rules:Section I:The Ball