Magic Mud

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For more than 80 years, Major League Baseball (MLB) has used a mysterious “magic mud” to improve grip on baseballs that gives pitchers a vital edge.

Now, scientists at the University of Pennsylvania confirmed what players have long believed: It really works.

The new study marks the first scientific proof of the mud’s effectiveness, known as the “Lena Blackburne Baseball Rubbing Mud.”

“It spreads like face cream, but it grips like sandpaper,” Doug Jerolmack, a geophysicist and co-author of the paper told NBC News. “It has this magical ability.”

Collected from a secret spot along the Delaware River, this unique mud’s blend of sticky clay and sandy particles improves baseball grip without damaging the leather.

Its use began after a 1920 tragedy when Cleveland player Ray Chapman was killed by a wild pitch. In 1938, Philadelphia Athletics coach Lena Blackburne remembered a fine New Jersey mud from his childhood, tested it, and eventually started a business selling it to baseball teams.

Today, Blackburne’s legacy lives on through Jim Bintliff, who still harvests the mud from the same family spot.

To test its “magical” properties, Jerolmack’s team ran three key experiments.

First, researchers measured the mud’s stickiness using an atomic force microscope, which helped them understand how well the mud clings to surfaces. Next, they tested how smoothly the mud spread by using a rheometer, which spun the mud to determine its thickness, affecting its even application on baseballs. Finally, they created a synthetic rubber “finger” coated in oil, mimicking human skin, to measure the grip between mud and leather.

These tests showed the mud’s unique mix of easy spreadability, perfect stickiness, and reliable grip, making it difficult to replicate and ideal for preparing baseballs.

MLB has tested alternatives, including synthetic coatings and “tacky” balls, but none can compete against the mud.

“This family is doing something that is green and sustainable, and actually is producing an effect that is hard to replicate,” Jerolmack noted in a statement.

The authors hope the findings will inspire new applications of natural materials in other fields.

“This is just a venue for us to show how geomaterials … can give us some exquisite properties that might be hard to produce from the ground up,” added co-author Paulo Arratia.