Charp Knowledge Sessions #1: Humidity parameters for collection care

Absolute humidity, relative humidity, vapour pressure and dew point describe the same air, but answer different questions. This webinar explains these parameters in plain terms and shows how monitoring data translates into risk for your collections.

Absolute humidity, relative humidity, vapour pressure and dew point describe the same air, yet answer different questions. They are among the most important parameters in collection care, and among the hardest to interpret with confidence. This webinar builds these concepts up from the ground, starting with the physics of water in air and in materials, and then illustrates them in a specific case: the Odilia shrine, where monitored humidity data was translated into an assessment of risk to the object.

Part 1: Theory (Prof. Staf Roels, Departement of Building Physics and Sustainable Design, KU Leuven, Belgium)

How much water the air holds, why temperature turns that into relative humidity, and how hygroscopic materials take up moisture, store thousands of times more of it than the air around them, and swell and shrink as a result. The session ends with the dynamics: how quickly an object follows a change, and why that matters more than a single reading.

Part 2 — Case: the Odilia shrine (Greet De Saedeleer, Director - Preventive Conservation Conservator, Object Care, Belgium)

From the client’s question to an assessment of risk: how monitored humidity values were translated, how actual damage processes were uncovered, through damage functions and the object’s moisture exchange with the surrounding air, into potential damage to the object, and what this means for interpreting your own data.

This webinar is for conservators, collection managers, facility managers and staff dealing with collections climate in museums, archives and heritage libraries.