Before every pitch in Major League Baseball (MLB), a finger-sized dollop of mud is meticulously applied to the ball. This special mud, Lena Blackburne Baseball Rubbing Mud, is scooped from a secret location in New Jersey. The MLB has repeatedly attempted to find synthetic replacements but has always failed. For scientists, this natural mud holds many mysteries.

Bringing Science to the Sedimentary Secret Sauce

Researchers at the University of Pennsylvania took it upon themselves to study this rubbing mud. In a series of tests, they discovered that the mud had the perfect ratio of clay, water, and sand. It smeared evenly like a skin cream while providing pitchers with extra grip due to its gritty texture.One of the researchers, geophysicist Douglas Jerolmack, was initially fascinated by the lore of this mud. Even after a quick analysis for a sports story, he couldn't stop thinking about it. Years later, chemical engineer-turned-geoinspired materials researcher Shravan Pradeep joined the team and continued to explore the muddy mystery.They detailed the mud's mineral composition, mechanical properties, and its effects on baseballs. About half of the mud consisted of quartz silt and sand, with smectite clays, mica, kaolinite, and illite making up the other half. The grain size distribution was typical, except for a drop-off in grains larger than 0.007 inch, which might hint at the sieve used.Fine-grained sediments adhere to each other via electrostatic forces, and clays seem to fill the pores in baseball skins, providing a more even and grippy surface. Larger sand grains roughen the surfaces, adding to the grip. The clay content also gives the mud the property of shear thinning, similar to skin creams.

The Potential of Geomimicry

Claire Chassagne, a physicist who studies sediments, pointed out that systematically varying the mud's composition would help identify any unique characteristics. The mud also contains organic compounds and additives that were not considered in this study but could make a significant difference.Pradeep believes that these results showcase the potential of looking to nature for cheap, sustainable, and ready-made geomaterials with desirable properties. Just as biomimicry is used in engineering designs, geomimicry could lead to the discovery of new materials with various applications.In conclusion, the mystery of MLB's rubbing mud continues to intrigue scientists. While they have made significant discoveries about its properties, there is still much to learn. The potential of geomimicry offers exciting possibilities for the future of materials.