Composite Materials Used to Make Baseballs

According to the American Composite Manufacturers Association, most of a baseball is made of composite materials. This organization defines a composite as "two or more dissimilar materials which when combined are stronger than the individual materials." Composites can be either natural -- such as wood, a combination of lignin and cellulose fiber -- or synthetic and man-made in origin. Both natural and synthetic composite materials are used in the manufacture of baseballs in a process that is said to date from 1872.

  1. Overall Baseball Construction

    • A baseball begins as a small cork-and-rubber ball encased in a rubber shell. Glue is applied to the shell and a series of four separate types of wool yarns is wrapped around the sphere. These spheres are spun in a machine with a latex adhesive to allow the glue to soak into the different layers of yarn. Two leather pieces in a "figure 8" shape are then wrapped around the ball and hand-sewn into place with 108 stitches of waxed red thread. After rotating in a press to compress the stitches tightly into the ball, a baseball is complete.

    Natural Composite Components

    • The wood cork in the small cork-and-rubber ball at the center of a baseball is the first natural composite component; both wood and rubber are considered natural composite materials. The latex adhesive applied to the outside of the small rubber ball core is another natural composite; latex is the polymerized sap of rubber trees. Finally, the wax applied to the red stitching of the leather cover is also a natural composite.

    Synthetic Composite Components

    • After wrapping the adhesive-covered ball core with three wrappings of differing ply natural wool yarn, the fourth and final layer of yarn is a polyester/wool blend, and therefore a synthetic composite component. The chemical adhesive allowed to saturate the balls after the four applications of yarn is also a synthetic composite.

    Reasons for Composites

    • The American Composite Manufacturers Association emphasizes that composites are used in place of completely natural materials because of the strength and durability they lend to the product. These qualities, required for a piece of batted sports equipment, are why so many composite materials are used in baseball construction.