I have been traditionally made from a spherical stitched envelope of leather or cloth stuffed with rags, horsehair or similar material, while I 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 me.
Originally I was made solely of rubber, but the wearing and playing properties of myself were improved by covering me with flannel stitched around the rubber 'core'. I 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original flannel cloth was replaced by special 'melton' cloth made specifically for the purpose and the stitching has been replaced by a vulcanised rubber seam.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, I was either black or white in colour, depending on the background colour of the courts. In 1972 the ITF introduced the yellow version of me into the rules of tennis, as research had shown that I am more visible to television viewers. Meanwhile Wimbledon continued to use the traditional white version of me, but eventually adopted the yellow in 1986.
My other properties have changed over time. The range of forward and return deformations - the change in my diameter under an increasing and decreasing load of 8.165 kg - have varied over the years, reaching their current values in 1996.
In recent years I have been discovered by the canine community and have become a great favorite there. I enjoy having a good romp with my new firneds as long as I am not destroyed in the process.
April 2008 Photo Contest Winner!
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This is Kyla! The winner of the April 2008 Photo Contest! Congratulations!!!