MLB's official rule book says that each ball must be “properly rubbed so that the gloss is removed.” And before each game, a clubhouse attendant rubs the balls to be used that night with the South Jersey mud.

Does MLB still rub mud on balls?

Soon enough, the National League would be using it as well. According to the official Lena Blackburne Baseball Rubbing Mud site, it is now used by Major League Baseball, the minor leagues, most independent leagues and many colleges.

What kind of mud do they rub on baseballs?

So, what do umpires use to prep the balls and dull the shine? New Jersey mud. For nearly three quarters of a century, a special variety of Jersey muck, Lena Blackburne Baseball Rubbing Mud, has been removing the sheen from baseballs for just about every professional baseball team in the country.