Control of relative humidity and temperature is decisive in the preservation of libraries and archival materials, for the reason that unacceptable levels of these accelerate significantly the deterioration of materials.

Library and archival materials are hygroscopic, giving off or absorbing moisture according to their surroundings, responding to changes in relative humidity by expanding and contracting. Dimensional changes accelerate deterioration and lead to visible damage as flaking ink, warped covers on books and cracked emulsion on photographs.

High relative humidity values can promote harmful chemical reactions in materials and, in combination with high temperature, encourage mould growth and insect activity. Low relative humidity values lead to dehydration, shrinking, cracking and embitterment of the paper materials and glue.

To guarantee optimal paper conservation the ambient should be between 18-20°C and 60-65%rh.  

Traditional humidifiers for libraries include humiSteam or compactSteam and for dehumification needs see our DryClim Dehumidifier.