Vaseline Ball (Grease Ball)

aka grease ball · greaseball · petroleum ball

Illegal since 1920. A spitball with grease, usually Vaseline, swapped in for spit because it's easier to hide. The lost friction makes the ball dive and break the same way. Outlawed, and throwing it is cheating.

Schematic baseball cover. This pitch has no filed seam geometry yet — the grip and shape below are sourced in words, not measured here.

The grip

Petroleum jelly (Vaseline) or a similar grease is substituted for saliva and worked onto the ball or the fingers, making the pitch slip at release the same way a spitball does but with a substance that is easier to stash and hide.

Reputable analysisSpitball — Wikipedia (saliva/Vaseline mechanism, 17 grandfathered pitchers, Grimes 1934, Perry)

What it does

Like the saliva spitball, the lost friction makes the ball dive and break unpredictably instead of carrying.

Reputable analysisSpitball — Wikipedia (saliva/Vaseline mechanism, 17 grandfathered pitchers, Grimes 1934, Perry)

What it really is

A grease-based variant of the spitball, covered by the same February 1920 ban on doctored deliveries. Gaylord Perry was its most notorious practitioner — he reportedly hid Vaseline on his zipper, betting umpires would never check a player's groin, and demonstrated throwing it with Vaseline and K-Y Jelly.

Reputable analysisGaylord Perry — Wikipedia (Vaseline/grease ball concealment, late-career ejection)

Perry's specific concealment methods are relayed through his own accounts and secondary reporting; they are anecdotal/self-reported rather than independently documented in-game findings.

Who throws itGaylord Perry (alleged)

Basic file

This pitch has a sourced one-line grip and movement and an honest explanation — not yet a filed specimen with authored grip geometry and a full craft chapter. A fuller breakdown is coming. Sourced, not corrected.