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Tennis ball

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Tennis balls at the 2012 French Open

A tennis ball is a small, hollow ball used in games of tennis and real tennis.[1] Tennis balls are fluorescent yellow in professional competitions,[2][3] but in recreational play other colors are also used. Tennis balls are covered in a fibrous felt, which modifies their aerodynamic properties, and each has a white curvilinear oval covering it.

Specifications

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A tennis ball sliced open to show its rubber bladder
Tennis balls and internal "blanks" manufactured by Dunlop Slazenger

Modern tennis balls must conform to certain 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). A tennis ball generally has 12 pounds per square inch (80 kPa; 0.8 atm) more of a nitrogen and oxygen mixture than the sea level ambient air pressure.[4][5] Yellow and white are the only colors approved by the ITF. Most balls produced are a fluorescent color known as "optic yellow", first introduced in 1972 following research demonstrating they were more visible on television. What color to call the ball is mildly controversial; one poll showed that a little less than half of people consider this color yellow, while a slight majority consider it green.[6]

Tennis balls are filled with air and are surfaced by a uniform felt-covered rubber compound. Tennis ball felts comprise wool, nylon, and cotton in a mixture surrounding the rubber edge.[7] The felt delays flow separation in the boundary layer which reduces aerodynamic drag and gives the ball better flight properties.[8][9] Often, the balls will have a number in addition to the brand name. This helps distinguish one set of balls from another of the same brand on an adjacent court.[10]

Tennis balls begin to lose their bounce as soon as the tennis ball can is opened. Tennis balls lose bounciness because the air inside the ball is pushing harder when a can is opened compared to when a ball is packaged. When packaged, the pressure in the can equally pushes the ball from the outside as the air inside the balls, preserving the pressure inside. When a tennis ball is unpackaged, its frequent use allows for air to escape from the ball.[11] They can be tested to determine their bounce. Modern regulation tennis balls are kept under pressure (approximately two atmospheres) until initially used; balls intended for use at high altitudes have a lower initial pressure, and inexpensive practice balls are made without internal pressurization. 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.[12]

Slower balls

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A training tennis ball

The ITF's "Play and Stay" campaign aims to increase tennis participation worldwide by improving how starter players are introduced to the game. The ITF recommends a progression that focuses on a range of slower balls and smaller court sizes to introduce the game to adults and children effectively. The slowest balls, marked with red, or using half-red felt, are oversized and unpressurized or made from foam rubber. The next, in orange, are unpressurized normal-sized balls. The last, with green, are half pressured normal sized.[10]

History

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Tennis balls, advertisement, 19th century

Lawn tennis, as the modern game was originally known, was developed in the early 1870s as a new version of the courtly game of real tennis. England banned the importation of real tennis balls, playing cards, dice, and other goods in the Importation (No. 2) Act 1463 (3 Edw. 4. c. 4).[13] 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.[14] 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.[15] 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.[citation needed] In the 18th century, 1.9 cm (3⁄4 in) strips of wool were wound tightly around a nucleus made by rolling several strips into a little ball.[16] String was then tied in many directions around the ball, and a white cloth covering was sewn around the ball.[citation needed]

Vintage, original white tennis balls (Slazenger Lawn Tennis Balls)

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 lawn tennis sets which included rubber balls imported from Germany. After Charles Goodyear invented vulcanised rubber, the Germans had been most successful in developing air-filled vulcanised 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.[17] Tennis balls were initially entirely made of rubber, but they were later refined by using flannel and stitching it around the core, which used to be filled with rubber. The tennis ball quickly switched to having a hollow core, using gas to pressurize the inside. Originally, tennis ball manufacturing was done by cutting vulcanized rubber sheets into a shape similar to that of a three-leaf clover. Before the formation of the rubber into a sphere (which was executed via machinery), chemicals that reacted to produce a gas were added to produce pressure into the hollow inside once the sphere was assembled. The switch to the modern method of joining two hemispheres was done to improve uniformity of wall thickness.[18]

Until 1972, tennis balls were white (or sometimes black). In 1972, the International Tennis Federation introduced yellow balls, as these were easier to see on television, and these quickly became generally popular. Wimbledon continued using white balls until 1986.[18]

Packaging

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Importation (No. 2) Act 1463
Act of Parliament
Parliament of England
Long titleCertain merchandises not lawful to be brought ready into this realm.
Citation3 Edw. 4. c. 4
Dates
Commencement29 April 1463
Repealed10 August 1872
Other legislation
Repealed byStatute Law Revision (Ireland) Act 1872
Status: Repealed

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)[19] cans with a full-top pull-tab seal and plastic lid fit three or four balls per can. Pressureless balls often come in net bags or buckets since they need not be pressure-sealed.

Disposal

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Recycling bin for tennis balls, at a sports equipment store in Spain

Each year approximately 325 million balls are produced, which contributes roughly 20,000 tonnes (22,000 short 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.[20]

In literature

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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.[21]

John Webster also refers to tennis balls in The Duchess of Malfi.[22]

References

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  1. ^ Oxford English Dictionary. Tennis ball (n.), sense a. "The small ball used in real tennis or lawn tennis."
  2. ^ "ITF Technical - History". International Tennis Federation. Retrieved 4 June 2015.
  3. ^ "Inside Wilson's tennis ball factory". ESPN The Magazine. 30 August 2015. Retrieved 2 November 2015.
  4. ^ Communications, Grainger Engineering Office of Marketing and. "Tennis Ball Facts". van.physics.illinois.edu. Retrieved 2023-04-01.
  5. ^ TennisCompanion (2017-11-18). "Ball in Tennis | Definition, Examples, and Common Questions About The Ball". TennisCompanion. Retrieved 2023-04-01.
  6. ^ Koren, Marina (2018-02-15). "What Color Is a Tennis Ball?". The Atlantic. Retrieved 2023-08-07.
  7. ^ Fischetti, Mark (April 2005). "Uniform Variety". Scientific American. 292 (4): 94–95. Bibcode:2005SciAm.292d..94F. doi:10.1038/scientificamerican0405-94. ISSN 0036-8733. PMID 15915818.
  8. ^ "Golf Balls, Cricket Balls and Tennis Balls". Princeton University. 5 October 2005. Retrieved 2009-10-20.
  9. ^ Dr. Rabi Mehta of NASA-Ames, entitled Aerodynamics of sportsballs, Annual Review of Fluid Mechanics, 17:151–189, 1985.
  10. ^ a b "Colors & Numbers on Tennis Balls". Epic Tennis Academy. 16 March 2013. Retrieved 2 September 2015.
  11. ^ Labmate, International. "How Long Before a Tennis Ball Loses its Bounce? And Where Does It Go?". Labmate Online. Retrieved 2023-04-01.
  12. ^ "ITF Approved tennis balls, classified surfaces & recognised courts — A guide to product & test methods" (PDF). International Tennis Federation. 2023. Archived (PDF) from the original on 19 July 2024. Retrieved 5 October 2024.
  13. ^ Bell, R. C. (1981). Board and table game antiques. Osprey Publishing. ISBN 0852635389.
  14. ^ Morgan, Roger (1995): Tennis, The Development of The European Ball Game, ISBN 0-9510251-8-X
  15. ^ "The Hammer Beam Roof". www.parliament.uk.
  16. ^ Cross, R. "Dynamic properties of tennis balls." Sports Engineering 2 (1999): 23-34.
  17. ^ Gillmeister, Heiner (October 1, 1998). Tennis:Cultural History. A&C Black. ISBN 9780718501952 – via Google Books.
  18. ^ a b "History of Tennis Balls" (PDF). International Tennis Federation. November 2019. Retrieved 2023-03-05.
  19. ^ Recycling, PETRA (PET Resin Association), retrieved 21 July 2010
  20. ^ "'New balls, please' for mice homes". BBC News. Retrieved 6 November 2015.
  21. ^ "When we have match'd our rackets to these balls, We will, in France, by God's grace, play a set" Henry V, act 1, scene 2
  22. ^ "We are merely the stars' tennis balls, struck and banded/Which way please them" The Duchess of Malfi, act 5, scene 4
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