Storing baseballs in humidors

Offense is down throughout Major League Baseball this season. For the first time since 2015, there was less than one home run hit per team, per game, for the month of April:

2022: 0.91

2021: 1.14

2019: 1.31

2018: 1.09

2017: 1.17

2016: 1.05

2015: 0.91

A number of factors are responsible for the reduction in home runs, and one of those factors involves how baseballs are being stored. During the 2021 season, 10 teams around the league stored their baseballs in humidors. This season, in 2022, all 30 teams are storing their baseballs in humidors.

Humidors are climate-controlled chambers that emulate the boxes used to preserve cigars. Humidors ensure baseballs are stored at average humidity. In places like Colorado and Arizona, where the parks are notoriously hitter-friendly, humidors prevent baseballs from drying out. This practice, therefore, helps pitchers, since dry baseballs have more bounce and can fly farther off the bat.

One would think the opposite effect would be true in the more humid ballparks, like Miami or Tampa Bay — that keeping the balls relatively dry would provide an advantage to the hitter. However, physics indicates that this is not the case. True, the dryer baseball would come off the bat at a faster rate. However, that lighter, dryer baseball would be flying into comparatively thick, humid air, which increases air resistance and slows the ball down.

The effect of humidors can be seen when comparing offensive numbers from 2021 to 2022 for teams that previously had humidors versus those for whom the humidor is a new addition this year.


Offensive numbers in the ballparks that already had humidors in 2021 look similar this season. However, in places where the humidor is debuting, offense is noticeably down around the league.

It does make sense that all 30 parks should be playing with the same baseballs, stored in similar conditions, as that can help preserve a more even playing field and reduce the varying effects of certain parks. This change could also be construed as a concession to pitchers, as humidors can make baseballs easier to grip.

Notably, the use of humidors isn’t the only change to the league’s baseballs this year. In response to the high home runs rates in recent seasons, tension was loosened on the first of three wool windings within the ball itself. Rawlings’ research prior to the start of the season estimated the adjustment would reduce the ball’s bounciness and also reduce the ball’s weight by 2.8 grams without changing its size. These changes were designed to lose one to two feet of distance on balls hit more than 375 feet.

It’s hard to tell with any definitiveness which of these factors is impacting offense more. It will be interesting to see how the season progresses, and whether offensive numbers remain consistently down through October.


Colorado Rockies humidor (AP Photo/Ed Andrieski)

A brief history of the baseball

The first baseballs were hand-made.  One of the first styles of baseball used in the mid-nineteenth century is known today as the “Lemon Peel” or “Rose Petal” baseball, due to the way it was stitched: a single piece of leather with four “petals” that were stitched around to cover the middle.  Inside the leather, a solid core was wound up in string or yarn.  The core itself could be any solid material, and sometimes, the baseball would also be stuffed with some other substance.  The leather used to make the ball was dark, since dark leather was readily available and it was easier for a player to spot a dark ball against a clear sky.  White baseballs were not used until 1861, when it was agreed that white would be easier to see against a backdrop of wooded surroundings.


Since they were typically made by players or local vendors, the first baseballs did not have a standard size or weight.  Until 1845, baseballs were also significantly lighter and softer than they are today.  One of the early rules of the game allowed that runners could be “soaked,” or hit with the ball, in order to be put out.  In 1857, the first baseball convention was held in New York, where fifteen New York teams voted on standard dimensions for the ball: it was to be 10 to 10.25 inches in circumference and to weigh 6 to 6.25 ounces.

“Figure Eight” stitched balls, which resembled the baseballs of today, were first created in the 1840s, though their use did not become popular until the 1870s.  These baseballs were not hand-stitched, but rather, professionally manufactured.  They were typically made to weigh 5.75 to 6 ounces and measured 9.75 to 10 inches in circumference.  By comparison, today’s regulation baseballs are required to weigh 5 ounces, measure 9 inches in circumference, and possess 108 stitches.  At the second baseball convention in 1858, it was determined that a baseball’s core was to consist of India-rubber, be wrapped in yarn, then covered in leather.


Credit: Rob L’s Baseball Memorabilia


In 1878, the Spalding baseball became the official baseball of the National League.  In 1883, Albert Spalding purchased Reach Sporting Goods, which had been supplying the official baseball of the American Association, thus giving Spalding a monopoly over the supply of major league baseballs.  The Rawlings baseball replaced Spalding’s in 1977.

Today, the core of a baseball consists of a cork nucleus, weighing half-an-ounce, which is encased in two rubber layers and then machine wound in nearly a mile’s worth of yarn.  This yarn-ball center is then coated in rubber cement and covered by two figure eight-shaped pieces of cowhide, which are sewn together with 108 cotton red stitches.






“Collecting Vintage Baseball Equipment.”  KeyMan Collectibles Newsletter.  Web.  Accessed 3 April 2013.

Miklich, Erik.  “Evolution of Baseball Equipment (Continued): The Baseball.”  19c Base Ball, 2007.  Web.  Accessed 4 April 2013.

“What’s That Stuff?: Baseballs.”  Chemical & Engineering News.  American Chemical Society, 1999.  Web.  Accessed 4 April 2013.