The mud is found during low tide, shoveled from the banks of the waterway and stuffed into buckets to be brought back to a garage at the Jersey Shore.

It has been harvested -- which is how Jim Bintliff describes the act of digging up mud -- in South Jersey for more than 80 years, ever since one of Connie Mack’s coaches discovered it could help grip baseballs.

And as Major League Baseball clamps down this month on pitchers using foreign substances to doctor balls, this mysterious mud remains the only agent approved by the league to be applied to baseballs.

But where exactly is it found?

“The way I describe it and the way it’s always been described, is it’s a tributary to the Delaware River on the Jersey side,” Bintliff said. “That’s the best I can do.”

The mud -- which is officially called Lena Blackburne Baseball Rubbing Mud -- is used by every team in both the major and minor leagues.

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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.

It takes Dan O’Rourke, the Phillies’ manager of equipment and umpire services, roughly 30 minutes to rub the balls before each game at Citizens Bank Park. The mud takes the sheen off the baseball, exposes the leather, and provides the pitcher with a better grip.

Other companies have tried to duplicate the mud and Major League Baseball tried recently to produce a baseball that no longer needs to be rubbed with mystery mud. But both failed.

“It’s the geology of the mud,” said Bintliff, who owns the company and runs it with his wife, Joanne. “The properties of it. It’s a real fine, super-fine abrasive. It’s all in the mineral content of the mud. They haven’t been able to duplicate it and they weren’t able to replace it.”

The use of foreign substances by pitchers emerged this season as baseball’s latest cheating scandal, causing the league to announce this week that pitchers will be suspended for 10 games if they are caught applying substances to the balls.

Beginning Monday, umpires will check pitchers throughout the game for sticky substances. Commissioner Rob Manfred said he determined that “new enforcement of foreign substances is needed to level the playing field.”

Pitchers had long used spit, pine tar, and sunscreen to get a better grip on their pitches. But the recent use of advanced substances like Spider Tack -- which is used to lift atlas stones in Strongman competitions -- was allowing pitchers to maximize the spin rate on their pitches.

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“It has become clear that the use of foreign substances has generally morphed from trying to get a better grip on the ball into something else -- an unfair competitive advantage that is creating a lack of action and an uneven playing field,” Manfred said.

Offense reached historic lows this season in both batting average and strikeouts, causing Major League Baseball to curb the practice of doctoring baseballs in hopes that it would inject more action into a game desperate for it.

“This has been a rule in baseball forever, and you took it upon yourself to start using it,” Phillies manager Joe Girardi. “Now they’re saying you can’t, but you weren’t supposed to use it before. It’s an admission of guilt to me.”

Now MLB will try to make sure the only foreign substance added to the ball is the mud that is found somewhere in South Jersey.

Mud harvest

The mud story begins in 1938, when an umpire complained to Russell “Lena” Blackburne, a third-base coach for the Philadelphia A’s, about the condition of the baseballs after they were prepped for the game by simply using water and infield dirt.

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The mixture made the covers soft and easily tampered with. So Blackburne, who grew up in Palmyra, tried using mud from the same South Jersey tributary that Bintliff now digs his harvest. It worked, as the mud removed the sheen from the ball but did not soften the cover.

Every American League team would soon use Blackburne’s mud and eventually the National League was on board, too. Blackburne played parts of eight seasons in the majors for four teams and managed the White Sox for two seasons before joining Mack’s staff.

Shortly before his death in 1968, Blackburne gave the mud business to Bintliff’s grandfather, John Hass. The company then moved to Bintliff’s father, Burns Bintliff. The mud business became Jim Bintliff’s in 2000 and he calls it a labor of love.

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“My grandfather had it given to him in 1965. I was 9 years old,” said Bintliff, who retired in 2015 from his job as a printing press operator after 33 years. “I can remember going out the first time to help him get some mud. It’s so unique. I think it’s really neat and I feel like I’m part of the game. I’m proud to be the guy who supplies the mud. I’m proud to carry on the family tradition.”

The mud business has expanded outside of baseball. Bintliff said half of the NFL teams -- and a growing list of colleges -- apply the mud to their footballs.

“Man, football is kicking my butt,” he said of the increased business.

The Bintliffs do not advertise or make sales pitches. The product sells mostly by word of mouth.

Bintliff goes out seven or eight times a year for a harvest, driving his pick-up truck from his home in Longport, N.J., to the same mud hole that his grandfather used. He brings help, he said, and a good harvest can yield as much as 20 five-gallon buckets filled with mud.

He brings the mud back to his garage, filters it, and washes it.

“That’s pretty much it,” he said. “I like to compare it to wine. I let it age a little bit. After five or six weeks after I harvest it, it’s ready to go.”

The mud is then packaged and sent to ballparks across the country. Every baseball this season -- just like it has been for decades -- is rubbed with Bintliff’s mud.

And if Major League Baseball’s crackdown is successful, it will be the only foreign substance added to the ball. But MLB still won’t know where to find it.

“It’s kind of funny when you think about it,” Bintliff said. “I’m just this man in Longport who has mud in his garage.”