Relative Humidity

Relative Humidity

Relative Humidity (RH) refers to the amount of moisture present in the air compared to the maximum amount the air can hold at a specific temperature. It is expressed as a percentage and is a critical factor in the preservation and display of artwork, documents, and framed objects.

Importance in Art and Framing

• Excessive humidity can cause warping, mold growth, and deterioration of paper, canvas, wood, and mat boards.
• Low humidity can lead to drying, cracking, and brittleness of materials.
• Maintaining stable RH levels is essential for archival storage and conservation framing practices.

Recommended Levels

• For most framed artwork: 40-55% RH.
• For sensitive works such as watercolors, photographs, or historic documents: 45-50% RH.
• Rapid fluctuations in RH are more damaging than consistently high or low levels.

Control Methods

• Use of climate-controlled storage or display environments.
• Employing desiccants or moisture-absorbing materials within frames or storage boxes.
• Use of zeolites or other humidity-buffering agents in enclosed display environments.
• Monitoring RH with hygrometers and adjusting HVAC systems accordingly.

Related Terms

• Archival Storage
• Climate Control
• Desiccant
• Zeolites