How Are Baseballs Made?
Official baseballs begin with cork centers, which are covered with a bouncy rubber cover. Machines build the balls to the correct, specified size by tightly wrapping layers of cotton and wool yarn around the rubber centers. Workers then dip the wrapped balls in rubber cement. This glue holds the inside of the ball together. A machine cuts the covers for the balls out of white leather. Finally, workers sew the covers on by hand.
The production of a baseball can be viewed as a process of placing successive layers of material around a small rubbery sphere not much bigger than a cherry. These materials are placed in three distinct ways: the rubber is molded, the fabric is wound, and the cowhide is sewn. The placement of materials around the sphere is done under carefully controlled conditions to ensure that consistent size, shape and quality are maintained.
In professional games the balls quickly become too dirty and scuffed by bats to use, or get lost in the crowd on a foul ball or home run. To feed the demand, the factory turns out as many as 2.4 million baseballs a year, all of which are made in the exact same way.
The baseball has undergone only one significant change since 1974, a shortage in the supply of horses prompted a switch from horsehide to cowhide covers. The size of baseballs and the raw materials used to make them are likely to remain unchanged in the foreseeable future. Also, few, if any, changes are expected in the process by which baseballs are manufactured.