For many classes of object[s] containing hygroscopic material (such as canvas paintings, textiles, ethnographic objects or animal glue) a stable relative humidity (RH) is required in the range of 40–60% and a stable temperature in the range 16–25°C with fluctuations of no more than ±10% RH per 24 hours within this range.
More sensitive objects will require specific and tighter RH control, depending on the materials, condition, and history of the work of art. A conservator’s evaluation is essential in establishing the appropriate environmental conditions for works of art requested for loan.
The AICCM recommended Interim Temperature and Relative Humidity Guidelines for acceptable storage and display conditions of general collection material are:
Temperature – between 15–25°C with allowable fluctuations of +/-4°C per 24 hr
Relative Humidity – between 45-55% with an allowable fluctuation of +/- 5% per 24 hr
Where storage and display environments experience seasonal drift, RH change to be managed gradually across a wider range limited to 40% – 60%
Temperature and Relative Humidity parameters for preservation of cultural materials will differ according to their material, construction and condition, but stable conditions maintained within the parameters above are generally acceptable for most objects.
AIC Interim Guidelines endorsed by the Association of Art Museum Directors:
For the majority of cultural materials, a set point in the range of 45-55% relative humidity with an allowable drift of +/-5%, yielding a total annual range of 40% minimum to 60% maximum and a temperature range of 59-77oF (15-25oC), is acceptable.
- Fluctuations must be minimized.
- Some cultural materials require different environmental conditions for their preservation.
- Loan requirements for all objects should be determined in consultation with conservation professionals.