The Society of Rheology and Physics Today Present:
Webinar Series | Editor’s Choice
Soft Matter Mechanics of Major League Baseball’s Rubbing Mud
April 22, 2026 | 11am EDT
Presenters:
Dr. Shravan Pradeep, Prof., Douglas J. Jerolmack, Prof. Paulo E. Arratia, University of Pennsylvania
and
Alex Lopatka, Physics Today
About this Webinar
For nearly a century, Major League Baseball has relied on a peculiar tradition: rubbing every new baseball with mud harvested from a secret location along a New Jersey river. While this practice has been trusted by players and umpires alike, the scientific basis for why this particular mud works has remained a mystery. Is it genuine mechanical behavior, or simply baseball superstition?
This webinar presents a comprehensive soft matter investigation that finally answers this question. Using multiscale rheological and tribological techniques designed to mimic baseball-relevant conditions, from the application of mud to the gripping and throwing dynamics, we reveal three distinct mechanisms by which Rubbing Mud transforms baseball surfaces.
The webinar will explore how the mud’s unusual composition creates a material that “spreads like skin cream and grips like sandpaper”. We’ll examine the rheological measurements that reveal the mud’s shear-thinning behavior, driven by clay and organic cohesion, which enables it to uniformly fill pores in the leather surface. Tribological experiments demonstrate how the cohesive residue doubles contact adhesion while sparse angular sand grains, bonded by clay particles, create a studded surface that enhances friction.
Beyond baseball, this work addresses broader challenges in sustainable materials engineering. The investigation demonstrates how natural geomaterials can achieve seemingly contradictory properties, high spreadability yet strong grip, through optimized proportions of cohesive, frictional, and viscous elements. The techniques and insights presented have implications for developing sustainable materials for lubrication and gripping applications, modeling natural hazards like mudslides, and understanding locomotion in muddy environments. Attendees will gain both specific insights into an iconic sports tradition and general principles for characterizing and engineering soft matter systems with tailored mechanical properties.
About the Physics Today Editor’s Choice Webinar Series:
Hear from innovative researchers addressing real-world challenges in this bespoke series from Physics Today. The Editor’s Choice webinar series runs throughout the year and comprises a range of popular topics hand-selected by the Physics Today editorial team based on their alignment with our audience’s diverse interests.
To view all Physics Today upcoming and on demand events, visit our webinar page .
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The Society of Rheology is an international community of rheologists committed to advancement and promotion of the rheological sciences and practice of rheology broadly across diverse groups of individuals, disciplines and industries.
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