<ul><li>Since 1938, every ball in Major League Baseball has been covered in a special “rubbing mud” harvested from a secret location in New Jersey.</li><li>Researchers studied the composition and rheology of the mud and found it to be a typical river mud with clay, silt, and sand particles.</li><li>The mud fills in pores and imperfections, creating a more uniform surface on the baseballs.</li><li>The residue of the dried mud doubles the ball's contact adhesion and the large sand particles add friction, resulting in a grip like sandpaper.</li></ul>

Baseball’s Mysterious Rubbing Mud

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