Study reveals science behind baseball's 'Magic Mud'

A new study has revealed the science behind Lena Blackburne Baseball Rubbing Mud, a specialized substance applied to Major League Baseball (MLB) baseballs to make them easier to grip. In a paper published in the *Proceedings of the National Academy of Sciences* (PNAS), researchers at the University of Pennsylvania detailed the unique properties of this naturally occurring substance, which has been harvested since the 1930s by the Bintliff family at a secret location along the Delaware River estuary in southern New Jersey.

The research team, led by geophysicist Douglas J. Jerolmack and including first author and doctoral student Shravan Pradeep, performed a series of mechanical analyses to uncover what makes the "magic mud" special. They measured its stickiness, spreadability, and frictional effects, providing the first published scientific evidence that its power is more than myth. According to the team, the mud possesses a unique combination of clay, water, and sand, making it perfect for application to baseballs and improving grip for pitchers by reducing the balls' slickness.

"It spreads like a skin cream and grips like sandpaper," Pradeep said, echoing Jerolmack's description of its unique properties. Jerolmack added, "When you take a dollop out of it and you put it on your hand, it's just like a nice facial cream and feels smooth. It doesn't feel gritty at all when it's a dollop of paste in your hand. It's after you spread it that it dries and feels gritty."

The researchers' interest in the mud began after an informal analysis of the substance five years ago, leading to a more detailed study at the request of sportswriter Matthew Gutierrez in 2019. Two years later, when Pradeep joined the labs, he took the lead in devising three sets of experiments to determine if the mud actually works, including measuring its spreadability and stickiness. The team developed three key tests: one to measure the mud's spreadability, one to measure its stickiness, and one to measure its effect on baseballs' friction against the fingertips.

First, they analyzed the mud's adherence, or stickiness, by using an atomic force microscope, which measures the mud's resisting force as an instrument pulls away from it. Second, to understand how well the mud flowed, they placed some on a machine called a rheometer that spun the sample and measured its viscosity. "The rheometer measures spreadability," the team noted. To simulate the effect of human grip on baseballs, the researchers had to build a new experimental setup. They constructed a synthetic rubber "finger" that mimicked the properties of human fingers and covered it with oil similar to that secreted by human skin.

"We needed to have a consistent finger-like material. If we just held our fingers to it, it wouldn't produce very consistent results," said co-author Xiangyu Chen, a senior in Mechanical Engineering and Applied Mechanics (MEAM) who played a key role in devising the artificial finger apparatus. The team carefully rubbed the oiled material against strips of baseballs that had been mudded in the manner specified by Major League Baseball.

The instruments revealed that the mud has the right amounts of stickiness, spreadability, and friction to allow pitchers to get a good grip on the ball. Jerolmack said, "It has the right mixture to make those three things happen: spreading, gripping, and stickiness." The researchers found that the mud has the perfect proportions of fine, sticky particles and sparse amounts of large, angular particles, which contribute to its unique texture and performance. "It's the fact that it spreads as if there's no sand in it at all. But once it dries, the sparse amount of sand that is there provides this friction effect," Jerolmack explained.

Lena Blackburne Baseball Rubbing Mud has been a staple in Major League Baseball since 1938, when Lena Blackburne, a third-base coach for the Philadelphia Athletics, discovered a fine filtered mud from his childhood in New Jersey. The mud comes from a secret spot along the banks of a tributary of the Delaware River and has been harvested by the Bintliff family since the 1930s. "The mud was so popular that Lena Blackburne created a business of processing and selling it," NBC News reported.

Today, each MLB team's equipment manager applies the magic mud to every game ball to enhance grip and reduce slipperiness. Since 2022, Major League Baseball has mandated that at least 156 baseballs get prepared for every game, each getting at least a 30-second rub with the mud within a three-hour period. The mud works as a superfine abrasive and takes the gloss coating off without damaging the leather or laces. "This stuff works," Jerolmack said.

Despite the mud's ubiquity, no one had been able to explain the science behind why it makes baseballs easier to grip or provide empirical proof that it worked until now. Major League Baseball has explored replacing the magic mud with synthetic lubricants but has not found a viable substitute, as attempts to replicate the mud's properties have failed. "It's a very special combination of ingredients that nature makes that make it work," Jerolmack said. The authors concluded that any attempt to create a synthetic substance to replace the mud—something Major League Baseball has explored—would be foolish.

Beyond baseball, the researchers hope their work and the mud's star status will spark more interest in the use of natural materials as lubricants. The study furthers the concept of "geomimicry," which looks to natural substances to create more sustainable materials. "This is just a venue for us to show how geomaterials are already being used in a sustainable way, and how they can give us some exquisite properties that might be hard to produce from the ground up," said co-author Paulo Arratia, a fluid dynamicist at the University of Pennsylvania.

The study was conducted at the University of Pennsylvania School of Engineering and Applied Science and School of Arts & Sciences and was supported in part by the National Science Foundation (NSF) and other grants. Additional co-authors include Ali Seiphoori of the University of Pennsylvania and the Norwegian Geotechnical Institute, and David Vann of the University of Pennsylvania.

The researchers hope their work can lead to more study of mud properties and understanding erosion. Pradeep said, "Nature creates these materials and we were able to look at their mechanical properties. So there are other materials out there which we don't know what they do, but have exotic mechanical or transport properties that we might want to look at. They could be an inspiration for a different group of lubricants or gripping materials to engineer them."

Sources: Popular Science, Home, NBC News, Science Daily, The Daily Caller

This article was written in collaboration with generative AI company Alchemiq