What is rosin and is rosin allowed in MLB?

Explaining what rosin is in baseball and looking into if it’s allowed in MLB with the league’s crackdown on pitchers with the sticky substance rules. 

On Wednesday, April 19 in the early parts of the 2023 MLB season, New York Mets ace Max Scherzer was ejected from his start against the Los Angeles Dodgers after a sticky substance check that the umpire determined he had something on his glove and hand.

Baseball has cracked down with strict sticky substance rules in MLB to try and essentially help hitters who were facing absurd spin rates and pitching, assumedly thanks to some assistance that is now banned by the league.

However, there is some confusion about rosin in this matter. Scherzer was clearly seen defending himself, saying that the stickiness was the result of rosin. That led to many baseball fans wondering if rosin is illegal in MLB and, more importantly, what exactly is rosin?

What is rosin in baseball?

If you’ve ever seen the millions of instances in a baseball game with the pitcher tossing the bag on the mound, that is the rosin bag. The white bag is filled with rosin powder, which is a sticky substance derived from the sap of fir trees, that helps pitchers combat sweat and moisture to get a firm grip on the baseball. It is considered the only officially legal “sticky substance” in MLB.

Is rosin allowed in MLB?

As mentioned, yes, rosin is the only sticky substance allowed in MLB. The powder’s ability to fight sweat on the mound is crucial to not necessarily gain spin rate, which is what the rules were designed to crack down on but, instead, to make sure they can grip the ball normally and have full control of their pitches. In reality, it can be as much about safety as it is helping the pitcher in his plight.

Having said that, there are specific rules that apply to rosin.

In a memo sent out to MLB teams and umpires in 2022, the league said that, in light of the crackdown on sticky substances, pitchers are allowed to use the rosin bag on their hands, wrists and forearms. However, they are “prohibited from applying it to their gloves and uniforms, nor are they allowed to combine rosin with any other substance, such as sunscreen.”