From the center of pressurized rubber to the felt cover, the materials made by the Man make up a lot of tennis balls. In some cases, PET recycled plastics are used to make the felt covers of tennis balls. The International Tennis Foundation establishes rules to govern the standard size, composition and color of official tennis balls.
Today's tennis balls are made of an empty shell of two pieces of rubber covered with pressurized gas. The rubber cover is covered by felt made of nylon or wool. The ITF stipulates that tennis balls should be between 2 1/2 and 2 5/8 of an inch in diameter and weigh between 2 and 2 1/16 of an ounce. The felt used to cover the tennis balls intended for official matches of bright yellow.
Manufacturers of tennis balls mold rubber into two forms that are pressed together to form the center of the ball. To achieve the proper level of rebound, manufacturers inject a specific amount of pressurized air into the center of each rubber core. The manufacturers polish the sealed balls with pressurized rubber and cover them in glue. The machines cut pieces of bright yellow felt into two shapes that wrap around the tennis ball to form its cover. Manufacturers heat the entire tennis ball to make the glue form a seal that holds the two pieces of fabric together.
Tennis was played for the first time in 1870 and the first tennis balls were made of leather or cloth and filled with rags and horse hair. Rubber tennis balls were developed in India and quickly became the standard for grass tennis matches. Players added flannel covers to rubber tennis balls to increase their durability. To increase the bounce ability of the ball, manufacturers began adding pressurized air to the center of the rubber core. Originally, tennis balls were black or white, but the ITF introduced yellow tennis balls in the 1970s because the bright color made tennis balls easier to see on television.
The ITF stipulates that tennis balls should bounce between 53 and 58 inches tall after being thrown onto a concrete floor from a 100-inch elevation. To achieve this precise height of rebound, the manufacturers of tapered balls add a very specific amount of air in the center of the tennis balls. In general, the balls are pressurized to 12 pounds psi.