The physics of baseball's most popular illegal pitches.

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Oct. 23 2006 6:50 PM

How To Throw the Goopball

The physics of baseball's most popular illegal pitches.

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Detroit's Kenny Rogers and his mysterious goo. Click image to expand.
Detroit's Kenny Rogers

Detroit's Kenny Rogers may not have been playing by the rules when he pitched his team to victory in Game 2 of the World Series on Sunday. Television footage showed some goopy black stuff smeared on Rogers' palm as he started the game. (Video footage shows similar stuff on his hand during his previous postseason starts.) Questioned later, Rogers said the stuff was "a big clump of dirt" that he used to get a better grip. How might the goop have given him an edge?

Daniel Engber Daniel Engber

Daniel Engber is a columnist for Slate

It depends on the goop. To be effective, a hurler has to vary the speed and movement of his pitches. He can do this legally by changing his grip on the ball and the spin he creates when he throws it. A pitcher who's willing to break the rules can create other effects by doctoring the surface of the ball. There are three basic techniques: He can scuff the ball, moisten it, or make it sticky.

To scuff a ball, the pitcher marks one side with whatever's handy. (Some pitchers rub the ball against the ground or grate it on a sharpened belt buckle. Joe Niekro was caught with an emery board and a square of sandpaper stuck to his finger.) The pitcher then has to throw the ball in such a way that the scuffed side stays in one place as the ball travels toward the plate. That creates unusual turbulence and can force it to swerve in one direction. (If the scuffed side spins, its effect on the air gets spread out and won't do much at all.) It's possible that Rogers used the goop on his hand to scuff up or alter the surface of the ball, but engineers who study pitching say it would take a lot of schmutz to get a useful effect.

Cheaters who don't scuff can throw the "spitter" instead. By lubricating the ball—with saliva, Vaseline, hair grease, or something else—the pitcher can throw a pitch that slides off his fingers without generating too much backspin. A greased-up pitch behaves kind of like a split-fingered fastball—it drops to the ground faster than a typical pitch. If Rogers had wet, slippery mud or clay on his hand, he might have been moistening up his pitches.

One Cardinals player suspected that Rogers had a sticky substance called pine tar on his hand. What advantage would sticky fingers provide? If a pitcher makes the ball sticky—or if he makes his fingers sticky—he might be able to get a tighter grip and throw the ball with more spin. A fastball with more backspin would stay up longer; a curveball with more spin would have a larger break.

Many people in baseball view doctoring with pine tar as a minor offense, at least compared with throwing scuffed balls and spitters. In 1988, the Dodgers' Jay Howell was ejected from a playoff game against the Mets for having pine tar in his glove. "I don't feel like I did anything wrong," said Howell. "If I'd scuffed, that's different." The Mets' team captain agreed: "I don't think a pitcher using pine tar is cheating … he's just trying to get a better grip. It's ridiculous."

Last year, Rogers' teammate Todd Jones defended the use of pine tar in a column for the Sporting News. "Pine tar is no big deal to players," Jones wrote. "Everybody uses pine tar. … It's almost a basic part of the game. Sandpaper and Vaseline, however, are looked at as cheating." (Jones had a neat explanation for the goop on Rogers' hand: "It could have been chocolate cake.")

Bonus Explainer: Some baseball researchers argue that a sticky ball could actually help the hitters. When a sticky ball makes contact with the top part of the bat, it's less likely to glance off as a foul ball. This allows the hitter to swing under the ball a bit and put backspin on it as he makes contact. The backspin could, in turn, make the ball travel farther off the bat.

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Explainer thanks Terry Bahill of the University of Arizona and Robert Watts of Tulane University.