Pine tar is most widely known as the sticky substance baseball players use on their bats to improve grip; the substance has also been used by mariners, in soaps, in roofing projects, and in the treatment of skin diseases since its discovery in the middle 1600s.
Pine tar is produced by a process called destructive distillation of the wood from a pines. The wood is rapidly decomposed by applying heat and pressure in a closed container; among the byproducts is pine tar.
Today, while it still has many other, lesser-known uses, pine tar is applied liberally to Major League Baseball bats all over the country every season. Because of its sticky texture, pine tar is used by batters to improve grip on the bat and prevent the bat from slipping out of batters' hands during hard swings.
Rule 1.10(c) of the 2002 Official Rules of Major League Baseball states that batters may apply pine tar only from the handle of the bat extending up for eighteen inches.
Famously, George Brett of the Kansas City Royals hit a seemingly-game-winning home run off of New York Yankees reliever Goose Gossage on July 24, 1983, which was ruled invalid by umpire Tim McClelland . The umpire ruled that the bat Brett had used was illegal because of excessive pine tar that extended beyond the allowed limit. The home run was disallowed, but the game was protested and appealed to the league office. The rule was re-written as a result to state that umpires may not disallow, after the fact, hits gained using bats with too much pine tar on them. American League President Lee MacPhail overruled McClelland and declared Brett's home run valid. The game was finished on August 18, with the Royals winning 5-4. This came to be known as the "Pine Tar Bat Game".
External Links
Major League Baseball Rules
Box Score of the Pine Tar Bat Game