Real Tennis balls are hand-made, following methods which have changed little down the centuries. Traditionally, a full set of tennis balls would number 108.
The earliest balls were known as esteufs – a name derived from the estouffes or etoupes of wool (latin: stups) from which they were made. Wool though, was costly: less conscientious ball-makers would stuff the dog- or sheepskin casings with any old thing: bran, barley or tightly-tied rags.
In 1461, Louis XI of France issued an edict ordering that Paumiers cease cost-cutting by making dangerous balls with chalk, sand, ash or sawdust. Shakespeare alludes to the use of human hair:
“The barber’s man hath been seen with him; and the old ornament of his cheek hath already stuffed tennis balls”
Claudio scoffs at Benedick: Much Ado about Nothing Act III, Scene II
Tennis balls have a hard core – in former times, of compacted cloth. During the Napoléonic wars, uniforms confiscated from French prisoners were cut into strips and recycled as balls for the Royal Tennis Court at Hampton. Those same balls were still in use when the Crimean War was being fought – and, ere long, strips from uniforms worn in that conflict would also make their way into the store cupboards of Britain’s Maître-Paumiers.
Today, tennis balls feature a cork core. Although some clubs now buy in machined spheres of solid Portuguese cork, Leamington uses old wine corks; Kevin strongly favours traditional, real cork over budget, agglomerated cork closures, however.
The core is covered by some ten metres of tightly-wound woven tape, then placed in a cup and beaten into shape. Possibly the most challenging part of ball-making is the tying of a tight lattice of criss-crossed string over the taped ball. Once this is done, two figure-of-eight shaped sections of dense melton wool cloth are hand-stitched together to form a cover.
The agreed parameters for the size and weight of tennis ball are as follows
Ball weight 72-78 grams
Ball diameter 62-66mm
For a detailed account of ball-making, see How to make the Real Tennis Ball – from core to cover by Sir Richard Hamilton, (pub. Tennis & Rackets Association, 1977)