Research has shown that the special mud rubbed on all MLB baseballs has unique, “magical” properties

Summary

• For years, every baseball game was rubbed with a special mud before every major league game to make it less slippery.

• The history of mud goes back to the 1930s, and the MLB still relies on one small supplier.

• A new study explains why it works: the mud has the perfect proportion of clay and sand.

For more than 80 years, baseball has used supplies of special mud that remove the shine from the smooth skin of balls and give fielders a better grip. The substance is rubbed into every baseball before every major league game.

It’s called Lena Blackburne Baseball Rubbing Mud, and it comes from a single source: a secret place along the banks of a tributary of the Delaware River. Jim Bintliff, a retired printing press operator in New Jersey, collects mud about once a month from his grandfather’s old fishing spot. He compares the consistency after processing to “cold cream, or maybe stiff pudding.”

Despite the ubiquity of mud, no one has been able to scientifically explain why it makes it easier to catch balls, or even provide empirical proof that it even works. Until now.

Scientists at the University of Pennsylvania developed a series of tests to examine the mud and even constructed a synthetic rubber “finger” to measure its properties. Their results, published Monday in the journal Proceedings of the National Academy of Sciencesprovide the first published scientific evidence that the power of mud is more than just a myth.

“It spreads like face cream but grips like sandpaper. It has this magical ability,” said Doug Jerolmack, a geophysicist at the University of Pennsylvania and co-author of the study.

Jerolmack’s team found that the mud had the perfect ratio of sticky clay and sand particles. The latter punctures the surface of the ball like barnacles to increase friction, and yet the material still spreads thinly and evenly, like toothpaste.

“The more you push it, the more it flows,” Jerolmack said.

The authors concluded that any attempt to create a synthetic substance to replace mud – something Major League Baseball was exploring – would be foolish.

“It’s a unique combination of ingredients that nature created that makes it work,” Jerolmack said.

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The story of how the mud was created is rooted in tragedy.

In a match in August 1920 New York Yankees pitcher Carl Mays he fired the ball toward Cleveland shortstop Ray Chapman and hit him in the head. Ball struck Chapman in the skull, killing him.

The death raised concerns about wild pitches and the risk of fresh, shiny baseballs slipping from pitchers’ hands. So in 1929, the president of the National League demanded that umpires start dirtying the balls to get better grip, according to the Baseball Hall of Fame.

However, finding the right substance proved difficult.

“They tried to take advantage of the goal dirt. It scratched the skin too much. They tried using shoe polish and tobacco saliva; those things clouded the ball too much,” Bintliff said.

Finally, in 1938, Lena Blackburne, third base coach of the Philadelphia Athletics, recalled the well-filtered muck of her childhood in New Jersey. He went back to the source, collected it and began to apply it.

The mud was so popular that Blackburne started a company to process and sell it. He eventually passed the business on to a childhood friend with whom he fished and sailed, whose grandson, Bintliff, now runs the business with his wife.

Starting in 2022, MLB requires at least 156 balls for each game, each receiving at least 30-second mud rubbing in three hours.

Bintliff said MLB buys mud barrels for each team for $100 each – two for the regular season and more for spring training. He added that some clubs, such as the World Series winners Dodgers, are purchasing additional containers for their farming systems.

“This mud acts as a very fine abrasive and removes the shiny coating without causing any damage to the leather or laces,” Bintliff said.

He collects the mud into 5-gallon buckets – usually about 10 to 20 buckets during a visit to the riverbank – and then processes it in his garage by draining river water, removing twigs and rocks, and adding tap water. This process produces an average of approximately 150 pounds of product.

Have any special ingredients been added?

“It’s a proprietary part,” he said.

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The scientists studying the mud are not avid baseball players, but became interested in it after conducting an informal analysis of the substance five years ago. Then two students from Jerolmack’s lab set out to see if the mud worked. They developed three key tests.

First, they analyzed the adhesion, or viscosity, of the mud using an atomic force microscope, which measures the drag force of the mud as the instrument moves away from it. Then, to understand how well the mud flowed, the researchers placed some mud on a machine called a rheometer, which rotated the sample and measured its viscosity.

The third test assessed the friction between human skin and a baseball; this involved constructing a synthetic rubber “finger” in which a drop of whale oil replaced the oil secreted by human skin. The “finger” was pressed against strips of leather baseballs and then spun on a rheometer.

According to Emanuela Del Gado, director of the Institute for Soft Matter Synthesis and Metrology at Georgetown University, the properties revealed in these tests are rare and sought after in cosmetics and other fields.

“In the industry, people spend a lot of time tweaking the formulation to achieve these types of properties,” said Del Gado, who was not involved in the research.

“For us, simple materials can be incredibly complex and can teach us a lot,” she added, noting that the mud has been shaped by currents, rainfall and long cycles of seasonal environmental change.

Bintliff currently counts college coaches, Little League referees and National Football League teams among his clients. He plans to pass the company on to one of his children.

So far, the mud has survived the new technologies that are fighting to replace it.

In 2016 Balls tested in the MLB league, coated with a proprietary chemicaland last year, commissioner Rob Manfred said the league was working with Dow Chemical develop a “sticky ball” that remains “pure white”. However, this project has not yet developed a solution to replace the mud, an MLB source said.

The study’s authors advise against giving up the mud, given new evidence confirming what soccer players first suspected more than 80 years ago: “It works,” Jerolmack said.