Baseball By The Numbers By Michael Salfino

September 1, 2006
Humidor Effect Called Into Question

A recent 2-1, 18-inning game at Coors Field has become Exhibit A in the prosecution’s case that the humidor used to store baseballs there has dampened them and scoring. The thin air at the stadium has increased runs anywhere from 24-to-40 percent in past years, but this year, runs are up a modest five percent.

The air hasn’t changed. So attention has turned to the humidor. Does this explanation, uh, hold water?

Former manager and current baseball announcer Buck Martinez is convinced. In a recent Denver Post article, he said, “…It’s changing the fundamentals of the game. It’s like going to a pitcher’s park and letting the hitters use aluminum bats.”

The Rockies began using the humidor in 2002 to counter the effects balls becoming dryer and lighter in the thinner air. Scoring dipped a little from 2002-to-2005, but Coors remained the best offensive park in baseball. This year, the Rockies reportedly began to leave the balls into the humidor for longer periods.

Physicist Robert Adair explained in his book “The Physics of Baseball” that the thinner air at Coors provides less resistance to fly balls and allows them to travel about nine percent farther than at a park at sea level. What does science have to say about the humidor? Could leaving the balls in longer alter them to the point where these altitude effects are completely cancelled out?

“I’d be very surprised if the weight of the baseball could be altered by more than one percent due to the humidor,” said Dr. Lawrence Krauss, Ambrose Swasey Professor of Physics and Astronomy at Case Western Reserve University. “That higher mass would result in a smaller acceleration and smaller distance traveled.” But Dr. Krauss said the reduction only would be equal to the increased mass of the ball.

“A one percent difference in the weight of a baseball could impact stats significantly,” he said. “And a softer, soggier ball could have more friction with the air and thus might travel lesser distance.

“But my best guess is that human factors are at play here. The humidor is known to the players. If they are intimidated and pitchers more confident, the effects could be self-determining.”

So, perhaps Coors merely has lost its mojo. But could all this just be a fluke? Can ballparks deviate far from average in a given year when it comes to runs scored and homers hit there versus what the same teams generate in other parks?

Absolutely. This season, Kauffman Stadium (Royals) has gone from reducing scoring by three percent in 2005 to increasing it 13 percent,  RFK Stadium (Nationals) from minus-20 percent to about neutral and Citizens Bank Park (Phillies) from plus-16 to plus-4.

As for homers, Coors has decreased from plus-12 percent to plus-5, nothing compared to U.S. Cellular (White Sox), plus-38 percent to plus-13.

Let’s see which individual players are most helped by their home environment and those most hurt and make some recommendations.

Buy

Chad Tracy, 3B, Diamondbacks: Chase Field is ridiculously homer-friendly this year, increasing from plus-5 percent to plus-35. Tracy has twice as many homers there as on the road, where he slugs a paltry .360.

Nick Markakis, OF, Orioles: Totally a product of Camden Yards, where homers are up 28 percent after being down five percent in ’05. Markakis is slugging well over .500 at home, but is around a Punch-and-Judy .400 on the road.

Chris Carpenter, P, Cardinals: The new Busch Stadium has really reduced homers, from plus-15 percent to minus-12. Carpenter takes advantage, allowing a puny .297 slugging percentage at home (.440 on the road).

Sell

Craig Monroe, OF, Tigers: He’s been a monster away from Comerica (.950 on base plus slugging percentage). At home, where homers are down 24 percent versus minus-6 in ’05, he has no claws (.688 OPS).

David Oritz, DH, Red Sox: A healthy Ortiz (irregular heartbeat) would have threatened Bonds’ homer mark: 30 road bombs,  but just 17 at Fenway (everyone seemingly a walkoff job).

Johnny Damon, OF, Yankees: Scoring is down 11 percent at the Stadium (plus-5 in ’05). Less real estate to Damon’s pull field has hampered his average (.273 at home, .327 away).