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.
Specifications Modern tennis balls must conform to
certain criteria for size, weight, deformation, and bounce criteria to be
approved for regulation play. The International Tennis Federation defines
the official diameter as 6.54–6.86 cm. Balls must have masses in the range
56.0–59.4 g. Yellow and white are the only colors approved by the ITF, and
most balls produced are a fluorescent yellow known as "optic yellow", first
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. 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. Modern regulation tennis balls
are kept under pressure 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 onto concrete; a bounce between 135 and 147 cm is
acceptable—if taking place at sea-level and 20 °C with relative humidity of 60%;
high-altitude balls have different characteristics when tested at
sea-level. Slower balls
The ITF's "Play and Stay" campaign aims to increase tennis participation
worldwide, by improving the way 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 effectively to both adults and
children. 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. History
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 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. Packaging
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 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 do not need to be pressure-sealed.
Disposal Each year approximately 300 million
balls are produced, which contributes roughly 20,000 tonnes 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 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. John Webster also refers to tennis balls
in The Duchess of Malfi. References
External links International Tennis Federation's
history of the rules of the tennis ball ITF Grand Slam Rules:Section I:The Ball