Study Finds Special Mud Rubbed on All MLB Baseballs Has Unique “Magical” Properties

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

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

• New research explains why it works: The mud has the perfect proportions of clay and sand.

For over 80 years, baseball used special mud that took the shine off the smooth skin of the ball and gave fielders better grip on the ball. This substance is rubbed onto every baseball before every major league game.

Called Lena Blackburn’s baseball mud, it comes from one source: a secret location on the banks of a tributary of the Delaware River. Jim Bintliff, a retired printing plant operator from New Jersey, collects mud from his grandfather’s old fishing hole about once a month. He compares its consistency after processing to “cold cream or maybe hard pudding.”

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

Researchers at the University of Pennsylvania have developed a series of tests to study mud and even constructed a synthetic rubber “finger” to measure its characteristics. Their results published Monday in the journal Proceedings of the National Academy of Sciences.offer the first published scientific evidence that the power of mud is more than a myth.

“It spreads like a face cream but lasts 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 proportions of sticky clay and sand particles. The latter is pressed into the surface of the ball like shells to increase friction, but the material is still distributed 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 dirt (as Major League Baseball has explored) would be foolish.

“It’s the special combination of ingredients that nature creates that makes it work,” Jerolmack said.

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The origins of mud are rooted in tragedy.

In play in August 1920 New York Yankees pitcher Carl Mays threw the ball toward Cleveland buddy Ray Chapman and hit him in the head. Ball hit 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 begin to dirty balls to improve grip. according to the Baseball Hall of Fame.

But finding a suitable substance was not easy.

“They tried to use the infield dirt. It scratched the skin too much. They tried using shoe polish and tobacco spit; those things darkened the ball too much,” Bintliff said.

Finally, in 1938, Lena Blackburn, third base coach for the Philadelphia Athletics, remembered the fine-filtered dirt of her New Jersey childhood. He returned to the source, collected it and began to apply it.

The mud was so popular that Blackburn created a business to process and sell it. He eventually turned the company over to a childhood friend with whom he used to fish and sail, whose grandson Bintliff now runs the company with his wife.

Beginning in 2022, MLB requires at least 156 balls to be prepared for each game, each receiving at least 30-second mud rub for three hours.

Bintliff said MLB purchases mud tubs for each team for $100 apiece — two for the regular season and more for spring training. Some clubs, such as the World Series-winning Dodgers, are purchasing additional containers for their farming systems, he added.

“This mud acts as an ultra-fine abrasive and removes the glossy finish without damaging the leather or laces,” Bintliff said.

He collects the sludge in 5-gallon buckets—usually 10 to 20 buckets per visit to the riverbank—then treats it in his garage by draining the river water, removing branches and rocks and adding tap water. This process produces an average of 150 pounds of product.

Are there any special ingredients added?

“It’s part of the property,” he said.

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The scientists who studied the dirt are not baseball fans, but they became interested in it after an informal analysis of the substance five years ago. After that, two students from Jerolmak’s lab went to see if the mud was working. They developed three key tests.

First, they analyzed the stickiness, or stickiness, of the mud using an atomic force microscope, which measures the drag force on the mud as the tool is lifted away from it. Then, to understand how well the mud flowed, the researchers placed it in a machine called a rheometer, which spun the sample and measured its viscosity.

The third test assessed the friction between a person’s skin and a baseball; it involved creating a “finger” from synthetic rubber with a drop of whale oil to replace the oils secreted by human skin. The “finger” was pressed against strips of leather baseballs and then rotated on a rheometer.

The properties identified by these tests are rare and sought after in cosmetics and other applications, according to Emanuela Del Gado, director of Georgetown University’s Institute for Soft Materials Synthesis and Metrology.

“In industry, people spend quite a lot of time adjusting the formulation to get this type of property,” said Del Gado, who was not involved in the study.

“Materials that are simple to us can be extremely complex, and they can teach us a lot,” she added, noting that mud is shaped by currents, precipitation and long cycles of seasonal environmental change.

Today, Bintliff’s clients include college coaches, Little League umpires and National Football League teams. He plans to pass the business on to one of his children.

So far, dirt has outlived the new technologies competing to replace it.

In 2016 Balls are MLB tested and coated with a proprietary chemical.and last year Commissioner Rob Manfred said the league was working with Dow Chemical to create a “sticky ball” that will remain “pure white”. But the project is no closer to a solution that could replace dirt, an MLB source said.

The study’s authors recommended sticking with the dirt, given new data confirming what ballplayers intuitively understood more than 80 years ago: “This stuff works,” Jerolmack said.