The remarkable qualities of baseball’s famous “magic” mud, utilized by MLB equipment managers on every World Series ball, have never been properly studied — until now. Researchers have uncovered the secrets behind the magic of this unique mud.
Until now, the extraordinary characteristics of baseball’s renowned “magic” mud had not been scientifically examined.
A recent study published in Proceedings of the National Academy of Sciences (PNAS) by scientists from the University of Pennsylvania’s School of Engineering and Applied Science (Penn Engineering) and School of Arts & Sciences (SAS) has unveiled what makes this mud so distinctive.
“It applies like a lotion and has a grip similar to sandpaper,” explains Shravan Pradeep, the lead author of the study and a postdoctoral researcher in the labs of Douglas J. Jerolmack and Paulo Arratia.
In 2019, responding to inquiries from sportswriter Matthew Gutierrez, the team examined the composition and behavior of the mud, which is traditionally collected by the Bintliff family from a hidden spot in South Jersey. This mud is applied to every game ball in Major League Baseball (MLB), including during this year’s playoffs. “We provided a quick analysis,” notes Jerolmack, “but it didn’t reach scientific validation.”
Although various articles and television features have highlighted the mud, featuring opinions from MLB players to the Bintliff family concerning its performance effects, the researchers did not find any scientific proof supporting claims that the mud enhances ball performance. “I was curious whether this mud’s use was more superstition than fact,” mentions Jerolmack.
Two years later, Pradeep took the initiative to create three different experiments to investigate if the mud was effective: one assessed its ability to spread, another evaluated its stickiness, and the third tested its impact on the friction experienced between baseballs and fingertips.
The first two properties were assessed using specialized equipment — a rheometer for spreadability and atomic force microscopy for stickiness — but for friction measurements, the researchers constructed a new setup that simulated human fingertip conditions. “We needed to quantify how the ball interacts with the finger along with the oils present,” says Arratia.
To tackle this, the researchers developed a rubber-like substance mimicking human skin elasticity, coated it with an oil resembling human skin oil, and then methodically rubbed this oiled surface against baseball strips covered in magic mud as per MLB specifications.
Xiangyu Chen, a senior in MEAM and a co-author of the study, played a pivotal role in creating this artificial finger device. “We required a consistent finger-like material,” he explains. “Using real fingers wouldn’t yield uniform results.”
The findings support what MLB players have long asserted: the magic mud is effective and not merely a superstition like playoff beards or rally caps. “It contains the right blend to enable these three functions: spreading, gripping, and stickiness,” states Jerolmack.
Despite MLB’s attempts to replace the magic mud with synthetic alternatives, they have so far failed to replicate its unique characteristics. The researchers advocate for continuing to use the original mud. “This family is engaged in a green and sustainable practice that’s producing results that are tough to replicate,” Jerolmack remarks.
Moreover, the researchers are hopeful that their study — along with the newfound fame of magic mud — will encourage broader interest in the use of natural materials as lubricants. “This presents a chance to demonstrate how geomaterials are already applied sustainably,” Arratia concludes, “and that they can provide remarkable properties that are challenging to create synthetically.”
This research was conducted at the University of Pennsylvania’s School of Engineering and Applied Science and School of Arts & Sciences, with support from various organizations including the National Science Foundation (NSF) and NASA among others.
Other co-authors include Ali Seiphoori from the University of Pennsylvania and the Norwegian Geotechnical Institute, and David Vann from the University of Pennsylvania.
