The materials used to create baseballs have evolved over time, from rubber to cork and from horsehide to cowhide. But the weight of official MLB baseballs has been the same since 1872. The Rawlings company has made all official MLB baseballs.
MLB Regulations
Official Major League Baseball regulations state that a baseball used in official MLB games must between 5 oz. and 5 1/4 oz. For official game use, a baseball must be shaped like a sphere and have a cork or rubber core surrounded by wrapped yarn. The ball must be covered in white horsehide or cowhide and sewn together tightly. Baseballs for official MLB game use must be between 9 and 9 1/4 inches in circumference.
Baseball Composition
The center of a baseball typically consists of a cork core that weighs 1/2 oz. and is 2 9/10 inches in diameter. The cork core is surrounded by a layer of black rubber and then a layer of red rubber. Each rubber layer weighs 7/8 oz. Then 121 yards of blue-gray wool is wrapped tightly around the rubber layers. On top of the blue-gray wool is a layer made from 45 yards of tightly wrapped white wool. The outer layer of white cowhide is adhered to the core of the ball using rubber cement and 216 red stitches.
Weighted Balls
Baseball pitchers often use weighted baseballs when practicing their pitching skills. Practicing pitching with a weighted baseball can help you improve the speed of your in-game pitches, according to the Complete Pitcher website. Weighted baseballs used for pitching practice typically weigh 6 oz. If you want to practice pitching with a weighted ball, make sure your arm is warmed up first to prevent injury. Only skilled pitchers should practice using weighted balls.
History
Baseball was first played in the late 1800s. When baseball was a new sport, the baseballs used in games typically weighed between 3 and 6 oz. In 1876, the National League was formed. The official weight for baseballs was then set to be between 5 and 5 1/4 oz. Rubber cores were used in game balls until 1911, when balls with cork centers became the standard. In 1931, official game balls began being made with cork cores surrounded with rubber layers.
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