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Tennis ball

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A Penn tennis ball.

A tennis ball is a ball designed for the sport of tennis, approximately 2.5 inches in diameter and are yellow-green in colour.

History

In the early days of tennis, balls were often made of leather stuffed with hair or wool. Early tennis balls were made by Scottish craftsmen. These tennis balls were commonly made 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 recent restoration were found to have been manufactured from a combination of putty and human hair, and were dated to the reign of Pope Leo X. 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, ¾" 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. This type of ball, but with a rubber core, is still used for the original game of tennis, today called real tennis. With the introduction of lawn tennis in the 1870s, vulcanized rubber was first used to manufacture balls, often in tubes of four with a package, but not with the name of the brand.

Modern balls

Modern balls are made from rubber mixed with 14 to 17 chemicals to get the proper consistency. Approximately 85% of the ball weight is the rubber/chemical mix. Over 90% of tennis balls are produced in Southeast Asia where the natural resource is abundant. The most expensive ingredient in the ball is the felt, which is adjusted in various ways to produce different properties. Steaming the felt raises its nap to make it fluffier, which increases wind resistance and control (through increased resistance when striking the players' rackets) while reducing bounce and speed. A compact nap causes the ball to skip on hitting the court or a racket.[1]

Pressureless balls

Pressureless balls usually have a stiffer, woodier feel than pressurized balls, and except for the Tretorn brand, they're not quite as bouncy new. 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 response changes from what you would expect of tennis balls.[2]

Standardization

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 "more than" 2 and 1/2 inches but "less than" 2 and 5/8 inches. Balls must weigh more than two ounces but less than 2 and 1/16 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 television. Tennis balls are filled with air and are surfaced by a uniform felt-covered rubber compound. 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.[3][4]

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 100 inches (2.5 m) onto concrete; a bounce between 53 and 58 inches (1.35 - 1.47 m) is acceptable (if taking place at sea-level and 20°C / 68°F; 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.

Disposal

Each year approximately 300 million balls are produced, which contributes roughly 32.3 million pounds of waste in the form of rubber that is not easily biodegradable. Historically, tennis ball recycling has not existed and the most common use has been to cut the ball into two semi-spheres and attach this to the bottom of chairs in schools, nursing homes and the like. Balls from the The Championships, Wimbledon are now recycled to provide field homes for the nationally threatened harvest mouse.

Notable manufacturers

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, The Duchess of Malfi

We are merely the stars' tennis balls, struck and banded
Which way please them

References

  1. ^ Feldman, David (1989). When Do Fish Sleep? And Other Imponderables of Everyday Life. Harper & Row, Publishers, Inc. p. 36. ISBN 0-06-016161-2.
  2. ^ Are pressureless tennis balls as good as regular, pressurized balls?, Jeff Cooper, About.com
  3. ^ What do the numbers on tennis balls mean and stand for?, Yahoo! Anwsers
  4. ^ Why are tennis balls numbered?, Jeff Cooper, About.com
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