Just as it was for the ancient Aztecs who played primitive games with a bouncing sphere thousands of years ago, rubber has been an essential ingredient in the balls used in America’s national pastime—baseball.

From the sport’s earliest days, baseball has been at the heart of American culture, and at the heart of the baseball itself has been rubber. During the dawn of baseball in the 1840s, players crafted homemade hardballs by wrapping whatever small objects they could find—rocks, walnuts and even fish eyes—with yarn before stitching a piece of leather around the orbs.

Soon, however, teams started to experiment with rubber cores. Zack Hample, author of “The Baseball: Stunts, Scandals, and Secrets Beneath the Stitches,” writes that shoemaker John Van Horn, a member of Brooklyn’s Baltic Base Ball Club who is recognized as the first commercial manufacturer of baseballs, cut strips from old rubbers shoes, wadded the material together and heated it until it could be molded into a spherical center of a baseball. According to Hample, the elastic baseballs resulted in such a scoring bounce that some teams plated over 100 runs in a single game.

While the National Association of Base Ball Players adopted rules in 1858 that required baseballs to have rubber cores covered with yarn and leather, the lack of precise regulations governing the ball’s weight, size and rubber percentage enabled home teams—which supplied baseballs for games—to tailor them to the strengths of their squads. Heavy-hitting clubs favored “lively” baseballs with added rubber, while slick-fielding squads relied on “dead” balls that were smaller and less bouncy.

Even in baseball’s infancy, there were controversies about whether baseballs have been “juiced” to stimulate scoring. Hample writes that the “first major juiced ball controversy in baseball history” occurred when the Washington Nationals were accused of using a hopped-up ball to defeat the previously unbeaten Cincinnati Red Stockings by a 53-10 score in 1867. Even for fans who enjoyed offense, the prolific scoring grew tedious, and when the newly formed National League restricted the rubber in baseballs to exactly one ounce in 1877, scores fell from their stratospheric levels.

Halves of two baseballs. On the left, a traditional cork-centered ball, and on the right, a rubber-centered ball used during World War II. (Credit: Roger Smith)
Halves of two baseballs. On the left, a traditional cork-centered ball, and on the right, a rubber-centered ball used during World War II. (Credit: Roger Smith)

Rubber remained the primary core of the baseball until 1910 when the A.J. Reach & Company began production of a ball with a center of cork encased in a layer of vulcanized rubber that had been patented the year before by Ben Shibe, owner of the Philadelphia Athletics. The new ball was not only more resilient and durable, but livelier as well since it was wound tighter to compensate for the use of the lighter cork at its center. It proved to be a fan favorite as well when it was used during the 1910 World Series and runs suddenly increased. When the American and National Leagues both adopted the cork-centered ball in 1911, the number of .300 hitters doubled and teams scored nearly a full run more on average.

Offense truly took over during the Roaring Twenties in what Baseball magazine called a “blind orgy of hitting.” While baseball fans were captivated by Babe Ruth swatting home runs out of ballparks at a record pace in 1927, few noticed Thomas Edison’s warning in Popular Science Monthly that the country would face a “rubber famine” in a second world war since America’s enemies would cut off supplies. “Lacking rubber, we would have to revert to balls stuffed with feathers or cork,” wrote the “Wizard of Menlo Park.”

Edison’s premonition became reality when the Japanese cut off rubber supplies after seizing Malaya and the Dutch East Indies at the onset of World War II. Four days after the 1941 bombing of Pearl Harbor, the United States banned the use of crude rubber in any items deemed non-essential to the war effort—including baseballs. While A.G. Spalding & Bros., which manufactured balls for Major League Baseball, had a large enough natural rubber inventory for the 1942 season, it was forced the following year to replace the core’s natural rubber shell with less-elastic balata, the same substance used to make the hard outer shell of golf balls.

From the first pitch of the 1943 season, players discovered that the balata ball was more than just dead. It was an “undertaker ball,” according to Boston Red Sox pitcher Tex Hughson. All four games on Opening Day resulted in shutouts, and as the season progressed, box scores sported more goose eggs than a poultry farm. At the end of April, the league was hitting a paltry .223.

Cincinnati Reds general manager Warren Giles, who complained the ball was filled with “ground baloney,” conducted his own experiment by dropping 12 of the new balls and a dozen of the prior year’s from the roof of Crosley Field and found the old balls bounced considerably higher. A more scientific study at Cooper Union found similar results. After first blaming cold weather and good pitching for the offensive drought, Spalding admitted the rubber cement applied between layers of yarn “proved of inferior quality” due to wartime restrictions that forced the company to substitute crude rubber with less-resilient reprocessed rubber. The replacement balls Spalding began to ship in May proved bouncier, but the average runs per game during the 1943 season dipped below four for the only time between 1919 and 1963.

By 1944, synthetic rubber production reached such a high level in the United States that Spalding was able to abandon the balata ball and resume normal manufacturing of baseballs. Two years later, the U.S. government lifted its wartime restrictions and crude rubber returned to baseballs once again.

Except for the wartime interlude, the baseball has changed little since the introduction of a cushioned cork center in 1931. Rubber remains an essential ingredient of the ball’s core with one layer of black semi-vulcanized rubber and another of red rubber cushioning the cork center and rubber cement coating layers of wound yarn. Over the decades, periodic surges in offense have renewed accusations of balls being juiced—and confirmed that the popularity of baseball controversies endure.