From SABR member David Kagan at The Hardball Times on May 1, 2019:
The first case study on the effect of humidors on baseballs goes back to 2002. The vagaries of mile-high baseball at Coors Field drove the decision to control the temperature and humidity in which the balls were stored. The typical humidity in Denver is about 30 percent, while humidors maintain 50 percent humidity at 70˚F.
Balls stored in the humidor have a higher water content than they would if they were stored in the Rockies dugout. The higher water content means the balls are “mushier.” In addition, they weight a bit more. As a result, such a ball will come off the bat with a lower exit velocity and thus won’t travel as far.
While home run numbers in the mountain air of Colorado remain high compared to other parks, they dropped about 13 percent from 2001 to 2002, demonstrably due to the humidor. The reason the home run numbers remain stubbornly above MLB averages is due to the thin air, which is a more difficult challenge to address. The Coors humidor remains in place to this day.
Read the full article here: https://tht.fangraphs.com/the-physics-of-humidors-a-second-case-study-at-chase-field/
Originally published: May 3, 2019. Last Updated: May 3, 2019.