Baseballs, like other pieces of equipment for the game of baseball, have changed a great deal since the sport's early days. In the late 19th century, sports equipment manufacturers patented cushion corks for use in the center of baseballs. During World War II, government restrictions on the use of certain materials forced manufacturers to switch to rubber centers, similar to those used in golf balls. While the construction of baseballs can vary, all manufacturers start with a rubber or cork center, wrap it in yarn and cover it in leather.
Mold the two hemispheric shells of black rubber to the sphere of rubberized cork. The hemispheric shells will not fully cover the cork, so seal the opening separating the two shells with the rubber gasket.
Mold the layer of red rubber to the black rubber encasement. Apply a thin layer of rubber cement to the surface of this sphere. The cement will hold the first layer of wool yarn in place.
Wrap all four types of yarn around the baseball's center in the following order: 121 yards of four-ply gray yarn, 45 yards of three-ply white yarn, 53 yards of three-ply gray yarn and 150 yards of fine poly/cotton finishing yarn. Professional manufacturers use a computerized winding machine for this process. If you are doing the winding by hand, be sure to roll the finished ball around on a smooth, flat surface to ensure a uniform surface for the center of the ball.
Use the scissors to trim any excess fabric from the yarn ball and cover the ball in a thin layer of rubber cement.
Cut the cowhide into two figure-eight patterns. Each pattern should cover half of the ball. Dampen each piece to ensure pliability, and cover the inside of each piece with a thin layer of rubber cement.
Staple the two figure-eight coverings to the wound ball, then hand-sew them together using the curved needle and the red waxed thread. Start stitching by inserting the needle from the between the two coverings to hide the knot at the end of the thread. Then insert the needle from the outside of the opposite covering, and draw the thread across both coverings. Tighten the loop and continue stitching back and forth across the edges of the two coverings. Each stitch should be separated by 1/6 of an inch, and you should make a lock knot after every six inches of stitch. A lock knot is the same as a shoe-lace knot, except without a bow. In total, a baseball will have 88 stitches and take 13 to 15 minutes to sew by hand.
Remove the staples and roll the ball on a smooth, flat surface to compress any raised stitches. Measure and weigh the ball to ensure that it is perfectly round.