Tennis ball

A tennis ball is a ball designed for the sport of tennis, approximately 6.7 cm (2.63 in.) in diameter. Tennis balls are yellow at major sporting events, but in recreational play can be virtually any color. Tennis balls are covered in a fibrous fluffy felt which modifies their aerodynamic properties. Before the development of lawn tennis in the early 1870s, the sport was played as the courtly game of real tennis. 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.[citation needed] In the 18th century, ?" 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.[citation needed] 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 65.41-68.58 mm (2.575-2.700 inches). Balls must weigh between 56.0 g and 59.4 g (1.975-2.095 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 (colour) television. The man credit

d with introducing the yellow ball in a tournament is Mike Davies Tennis Hall of Fame 2012 Tennis Hall of Fame Inductees]. In 2007, company Whitetennisballs.com brought white balls back to the mainstream market. 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 (53-58 inches) is acceptable (if taking place at sea-level and 20C / 68F 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. 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, such as the TreTorn MicroX, are more similar to the feel and play of pressurized balls, and last many times longer than traditional tennis balls Each year approximately 300 million balls are produced, which contributes roughly 20,000 metric tons of waste in the form of rubber that is not easily biodegradable. Historically, tennis ball recycling has not existed and the most common re-use has been to cut a hole in the ball and attach the ball to the bottom of chairs in schools, nursing homes and the like to prevent scuffing or scraping the floor.[citation needed] 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 US States and six countries.