'Real-tennis' ball featuring hand stiched seams
white 20th-century lawn tennis ball
yellow cloth was introduced in the 1970's
The game of tennis (more properly known as lawn
tennis) was developed in the 1870s from the game of royal or real tennis, which
has been played for centuries. While both games are similar, in that they are
both based on two or four players opposing each other from different sides of a
net hitting a ball back and forth, the type and size of court, method of
scoring, etc., are very different.
Real tennis balls have been traditionally made from a spherical stitched
envelope of leather or cloth stuffed with rags, horsehair or similar material,
while tennis balls have always been based on rubber.
From the beginning of lawn tennis in the 1870s, India rubber, made from a
vulcanisation process invented by Charles Goodyear in the 1850s, was used to
manufacture lawn tennis balls.
Originally tennis balls were made solely of rubber, but the wearing and playing
properties of the balls were improved by covering them with flannel stitched
around the rubber 'core'. The ball was quickly developed by making the core
hollow and pressurising it with gas. Originally, core manufacture was based on
the 'clover-leaf' principle whereby uncured rubber sheet was stamped into a
shape resembling a three-leaf clover and this was assembled into a roughly
spherical space by machinery adapted for the purpose. Chemicals generating
pressurising gas were added prior to closing the assembly and these were
activated on moulding the core to a spherical shape in heated cavities. The
process was used for many years until the precision of the game demanded a
higher degree of uniformity (particularly relating to wall thickness) than
could be obtained with the clover-leaf method. Now it is usual to compression
mould two separate 'half-shells' which are assembled together to produce a
'core'. The original flannel cloth was replaced by special 'melton' cloth made
specifically for the purpose and the stitching has been replaced by a
vulcanised rubber seam.
Historically, balls were either black or white in colour, depending on the
background colour of the courts. In 1972 the ITF introduced yellow tennis balls
into the rules of tennis, as research had shown these balls to be more visible
to television viewers. Meanwhile Wimbledon continued to use the traditional
white ball, but eventually adopted yellow balls in 1986.
Until high altitude balls were introduced into the rules in 1989, only one type
of tennis ball was allowed. The Type 1 and Type 3 balls were introduced into
the rules in 2002.
Other properties of the tennis ball have changed over time. The range of
forward and return deformations - the change in the ball's diameter under an
increasing and decreasing load of 8.165 kg - have varied over the years,
reaching their current values in 1996.