Welcome to The Ounce, an occasional missive for Harvard Library colleagues from Preventive Programs in HL Preservation Services.

The Dry Humidity Season: November-February

During the fall and winter season, indoor humidity levels drop, presenting risks for library and archive collections. Humidity below 40% is drying and can cause organic materials to shrink, warp, crack, or become brittle. These changes can be permanent or require conservation treatment to resolve.

If humidity drops lower than 30%, some materials are even more susceptible to these...