What is the recommended relative humidity range for storing books?

What is the recommended relative humidity range for storing books?

• A. 20-30%
• B. 40-50%
• C. 70-80%
• D. 50-60%

Answer: (D)

Maintaining a stable mid-range humidity is key to preserving books. Relative humidity influences how wet or dry the paper and bindings stay: if the air is too dry, paper fibers become brittle, inks can crack or fade, and glue or paste in bindings can fail. If the air is too humid, paper swells, warps, and becomes a haven for mold, mildew, staining, and pests. The recommended range around fifty to sixty percent strikes a balance, keeping paper flexible enough to avoid cracking while staying dry enough to limit mold and moisture-related damage. Choices that are too dry (twenty to thirty percent) or too humid (seventy to eighty percent) push us toward those failure risks.

Maintaining a stable mid-range humidity is key to preserving books. Relative humidity influences how wet or dry the paper and bindings stay: if the air is too dry, paper fibers become brittle, inks can crack or fade, and glue or paste in bindings can fail. If the air is too humid, paper swells, warps, and becomes a haven for mold, mildew, staining, and pests. The recommended range around fifty to sixty percent strikes a balance, keeping paper flexible enough to avoid cracking while staying dry enough to limit mold and moisture-related damage. Choices that are too dry (twenty to thirty percent) or too humid (seventy to eighty percent) push us toward those failure risks.