WASHINGTON (Reuters) - Shattered baseball bats pose real danger when shards of wood go flying, but this happens half as often as it did just five years ago after the U.S. Forest Service joined Major League Baseball to figure out how to make bats more shatter-resistant.
U.S. Agriculture Secretary Tom Vilsack announced the finding on Friday, in a statement timed to dovetail with baseball's All-Star Game on Tuesday.
The key is in the grain of the wood, said David Kretschmann, who coordinated the project at the Forest Products Laboratory in Madison, Wisconsin, with support from league management and the players' union, the Baseball Players Association.
No matter what wood a baseball bat is made of - traditional ash or the currently popular maple - the grain needs to be straight along the length of the bat, Kretschmann said in a phone interview.
Ash wood is naturally straight and its grain is easy to see in a baseball bat, while some kinds of maple bats can have what is called "slope of grain," where the grain goes at a slant, making them more likely to break.
Thousands of baseball bats break each season, including bats that crack but stay in one piece. Multi-piece failures - bats that shatter into two or more pieces when they hit the ball - are the hazardous ones.
Injuries caused to players or spectators by pieces of splintered wood can be serious, like the one suffered by Chicago Cubs outfielder Tyler Colvin in 2010, when he was hit in the chest with a piece of a maple bat that shattered.
In 2010, a New Jersey man sued the New York Mets after a 2007 incident in which a bat shattered by infielder Luis Castillo flew into his face, causing multiple fractures.
Kretschmann said that in 2008 there was an average rate of about one broken bat per game in the big leagues. Now, that rate is down to .46 per game.
"Multi-piece bat failures represented one of our foremost concerns," said Mike Teevan, an league spokesman. "We are very encouraged that the incidence rate on those has essentially been cut in half."
Maple bats have become popular over the last dozen years or so, comprising over 60 percent of all bats sold in 2012. Some observers attribute that popularity to slugger Barry Bonds' use of a maple bat in his record-breaking 73-home run season in 2001.
A maple bat feels different in the hand than a traditional ash bat and has a different sound when it hits the ball, Kretschmann said. Maple bats can be made more resilient to breakage if they are cut to minimize slope of grain.
Reporting by Deborah Zabarenko, editing by Ros Krasny and Philip Barbara