Relative Humidity

A thorough understanding of relative humidity, and the ability to explain it to non-conservators, is necessary for environmental monitoring and artifact preservation.

This tutorial does not attempt to examine the effects of differing relative humidity on specific materials, but it does cover the general basic concepts of relative humidity.

Before working through this tutorial read the sections on states of matter in the AS and A Level Chemistry Through Diagrams (Oxford Revision Guides) or a similar basic chemistry book.

In this tutorial, you will learn:

• That steam, like many other gases, can't be seen by the human eye
• How water evaporation and condensation are related to temperature and pressure
• That relative humidity is really a measure of relative vapor pressures
• What the dew point represents
• How relative humidity is measured using a sling psychrometer
• How to use a psychrometric chart

 Enter tutorial.

Useful links on this topic:

• AS and A Level Chemistry Through Diagrams (Oxford Revision Guides)
• JAIC Online
• Bradley, Susan; “Preventive Conservation research and practice at the British Museum”; JAIC 2005, 44 (3), 159-173.
• Hansen, Eric F.; Lee, Steve N.; Sobel; Harry; “The effects of relative humidity on some physical properties of modern vellum”; JAIC 1992, 31(3), 325-342.
• Scott, David A.; “Bronze disease: A review of some chemical problems and the role of relative humidity”; JAIC 1990, 29(2), 193-206.