If you look closely at the baseballs used in last month’s World Series, you will see that they are covered in a mysterious brown substance.
It wasn’t a mistake, and nothing illegal was found on the ball. It was just mud.
For decades, every ball used in Major League Baseball was coated with mud collected from a secret location along a tributary of the Delaware River in New Jersey. Only a few people knew its exact location, and until recently, only a few knew its exact contents.
Now researchers have dug deeper and discovered what they consider to be this clay’s surprising mechanical properties.
“It’s magical. It spreads like face cream and grips like sandpaper,” said Douglas Jerolmack, a professor in the Department of Earth and Environmental Sciences at the University of Pennsylvania and one of the authors of the paper published Monday in The Journal of the Proceedings. National Academy of Sciences.
Their research may be relevant for more than just studying baseball. The researchers say the techniques they used to understand how baseball mud behaves could be extended to developing sustainable materials for construction, agriculture and infrastructure.
“This research helps us find materials in nature that can replace the hydrocarbon-based materials we use today,” said Shravan Pradeep, a chemical engineer and postdoctoral fellow at Penn and another author of the study.
Baseball mud is part of the game’s mythology. Beginning in the 1950s, they were dug out along the Delaware River and then applied to new balls by clubhouse workers. They pick up a small amount from the container and apply it to the ball with their hands, leaving a thin brown film.
The reason for applying mud is because the manufacturer’s new ball is shiny and slippery, making it difficult for pitchers to catch. But the league allows pitchers to rub this substance, unlike other sticky substances they have tried using over the years, which is against the rules.
Where the mud comes from is a well-kept secret, but getting it isn’t difficult. The authors of the new study purchased a small bottle of Lena Blackburne Baseball Rubbing Mud for less than $30 from the company’s website.
They used a variety of tools to measure the composition, viscosity, friction and adhesion levels of the mud. They say that mud is made up of small particles of clay, quartz and other minerals, some sand, and very small amounts of material from plants and other living things. About 43% of its weight is water. The basic ingredients alone are neither surprising nor surprising. What makes clay special is the ratio of ingredients that give it two seemingly conflicting properties.
The mud spreads smoothly, but is a bit rough and sticky once it dries. The researchers found that angular particles in the sand appeared to play an important role. “The sand grains are held to the surface by the clay. Now you have a uniform layer with barnacle-like sand particles embedded in the surface,” Dr. Jerolmack said.
Researchers say this duality means that mud or similar substances can be used as both lubricants and friction agents. The mud can also fill the pores of the leather, making the surface of the ball more uniform, effectively doubling the contact adhesion, or stickiness, between the ball and the pitcher’s hand.
The companies that produce the mud are very secretive about the riverbanks from which the mud is harvested and their processing procedures. Researchers hypothesize that some filtering occurs, perhaps to reduce the proportion of sand. There may also be small additives. But they concluded that, as with many geological substances, years of production and observation helped the company arrive at the secret recipe.
“They know what they’re doing,” Dr. Jerolmack said. “This material has been processed to optimize its properties.”
In recent years, Major League Baseball has been exploring manufactured alternatives to clay. But researchers who conducted the new study say older products from the ground are effective and sustainable through tidal replenishment.
“You don’t have to use synthetic products,” said Paulo Arratia, a professor of mechanical engineering and applied mechanics at Penn.
The study’s authors said their method of studying clay could one day be applied to similar materials that could replace carbon-intensive building materials, but they acknowledged there were other motivations for conducting the study.
“It’s fun because it’s baseball-related,” said Dr. Pradeep.
