Museum collections are expected to last for a really long time. To preserve objects in a collection for a really long time, museums attempt to control the environmental factors that affect preservation. Too much light, humidity, heat and improper handling all contribute to deterioration. So with a conditioned building and good collections management practices, the likelihood of an object surviving for hundreds of years improves. Improving the microenvironment inside a building or storage room can even further increase the life expectancy.
Some situations do not require a lot of analysis. Many of the Northwest Railway Museum’s large objects have been stored outside for years. Getting those large objects into a building and keeping them dry has extended their life expectancy by many years.
Other situations - for instance the conditions inside the building - require more information before improvements can be identified and implemented. The best compromise of conditions would be 45% relative humidity and a temperature of 60 degrees Fahrenheit. However these conditions are difficult – or impossible – to achieve most of the year unless special air handling equipment is installed. A related factor affecting preservation is the rate of change for temperature and humidity. Simplistically, it is preferable to have constant higher humidity and/or temperature than optimal conditions that cannot be held constant resulting in daily fluctuations. Environmental monitoring allows a museum to determine what is occurring so that the best compromise can be reached, and to plan for long term improvements such as the installation of supplementary dehumidification.
A collections grant from 4Culture has funded the purchase of 10 environmental monitoring units. The solid state devices record temperature and humidity readings every 30 minutes and retain up to 10 years of data. The PEM-2 units are manufactured by the Image Permanence Institute at the Rochester Institute of Technology and are among the most trusted devices in the museum field.
The PEM-2 monitoring units have been placed inside the Museum’s buildings, and in storage areas where the most vulnerable objects – including photographs, paintings, and books –are stored. The data will be used to help establish priorities for environmental improvements by identifying obvious problems and trends that lead to problems.
Thanks to 4Culture’s support, the Museum is able to study the environment that collections are stored in. The data will be used to optimize the settings of the existing environmental controls, and to plan for future investment that will further improve preservation.
Photo: A PEM-2 device displaying 74% RH - much too humid for preservation.