Museums: environmental control guide
Why is it important to control humidity in the museums and fine art sectors?
This comprehensive guide outlines:
What is humidity, how is it controlled and what happens to works of art if humidity is not controlled. It also covers the important topic of of the effects of humidity on humans to ensure that your visitors as well as your collection can be suitably protected
Why is it important to control humidity in the museums and fine art industry?
The stability of the surrounding environment is a vital and basic factor in the conservation of art, requiring temperature and humidity to be strictly controlled.
Fluctuations in temperature and humidity caused by external factors, such as the weather or the number of visitors, are a major problem for museums. Fluctuations that occur repeatedly over a short period of time will have the most damaging effect as the materials do not have enough time to acclimatise.
For example, an influx of people at one time will increase the humidity considerably, especially on a rainy day.
Effects of humidity on art
Poor humidity control can cause irreversible damage to art and antiques made from a wide variety of materials. Maintaining specific humidity levels is often a condition of benefactors in deciding whether or not to loan works of art to galleries.
Most organic materials react with their surrounding environment and will absorb or desorb water accordingly from the air to become acclimatised or at ‘equilibrium’.
Consequently, many works of art within museums and heritage could potentially be damaged if relative humidity is too high or too low. For example, very low humidity
may cause shrinkage and cracking of panel paintings, or very high humidity could lead to distortion of paintings or corrosion of metals.
These effects may be very visible such as materials warping, splitting or cracking or they can be microscopic but over time will become more obvious. As works of art grow older they become brittle and fragile, and less able to readjust their internal moisture level without damage.
For most general collections, the acceptable band of humidity is between 40 – 60% RH at normal room temperature (17-25°C), with no more than 10% fluctuation over 24 hours.
Most heritage collection environments are now monitored for relative humidity and temperature surroundings with the plotting of analytical graphs, using electronic sensors
coupled with software-based data logging systems.
To correct high humidity, dehumidifiers are used and for low humidity problems, humidifiers are used.