Managing the Environment for Preservation: Our Philosophy

IPI has formulated a new definition of the preservation environment and has developed tools and procedures that allow cultural institutions to understand and improve long-term preservation of collections.

IPI’s view is based on thirty years of research into accelerated aging, equilibration rates, image stability, the effects of pollution, and material decay in general. IPI has put its research into practice at hundreds of institutions in the US and abroad, most significantly at the Library of Congress, the National Archives, the National Park Service, the New York Public Library, and the National Museum of Denmark. Over the last thirteen years, IPI has developed the best tools available to cultural institutions for monitoring, documenting, and analyzing the storage environment—these include the Preservation Environment Monitor® (PEM), Climate Notebook® software for data analysis, and the DewPoint Calculator. The most recent technology available to the preservation field includes the Myclimatedata websites, which were custom-designed for several large institutions, as well as the PEM2 and the PEMdata website.

Effective environmental management requires a nuanced view that considers the physical nature of the collection objects themselves and understands the mechanisms of decay to which the collections are most vulnerable.

Decades of preservation research at IPI and in other institutions have fundamentally altered our approach to managing the environment for preservation. Data from years of accelerated-aging tests on a variety of materials provide strong scientific evidence that heat and moisture are the primary rate-controlling factors in almost every form of decay. Research has also shown that no single environmental condition can ever be ideal—either for the different components of a composite object or for a collection of many types of objects. Choices have to be made based on the predominance of certain materials and their particular vulnerabilities.

IPI has developed preservation metrics, which transform temperature and humidity data into numerical estimates of collection decay risk and allow cultural institutions to assess the preservation quality of the storage environment.

Preservation metrics offer an alternative way to manage environments. Calculated from temperature and humidity data using algorithms developed by IPI, each metric integrates spans of time into a single value representing how the environment is likely to affect one particular form of deterioration, taking into account all the ups and downs of temperature and RH over time. Each metric measures a specific form of collection decay, including spontaneous chemical change in organic materials (natural aging), the risk of mold growth, metal corrosion, as well as mechanical decay based on excessive dryness, excessive dampness, and wide or frequent fluctuations in moisture that result in dimensional change.

Unlike targets and set points, metrics can quantify both the risks and benefits posed by any set of conditions over any period of time. The ability to integrate all the data you normally see on a chart or graph into a single numerical estimate of decay rate is a radical advance for the field of preventive conservation. Using metrics, collection care staff can easily assess the risk of collection deterioration and make appropriate changes to improve the preservation quality of the storage environment.

Preservation metrics have been used successfully in hundreds of institutions to manage and plan storage environments. All of IPI’s environmental monitoring and analysis tools—Climate Notebook and PEM2 as well as the PEMdata and Myclimatedata websites—are based on the use of preservation metrics.

IPI research has shown that the best way to achieve a storage environment that improves preservation quality is to take a long-term view.

The most effective strategy for museums, libraries, and archives is a proactive approach based on preventive conservation. We encourage institutions to move away from reacting to deviations from “ideal” ranges and to look more closely at long-term trends, particularly the seasonal extremes in temperature and RH.

The more common reactive approach encourages building operators to fix the immediate problem—if they can. Years of work within a number of institutions have shown that these reactions are unlikely to produce the desired result. Short-term (daily or weekly) fluctuations rarely matter to the collections in storage, and a quick fix of some part of the air-handling unit is not likely to improve the overall performance of the system.

IPI strongly recommends that a full year of temperature and relative humidity data be used for analysis. Seasonal variations in outdoor conditions are the most significant source of variation in indoor climates. Seasonal variations produce the most damaging extremes and pose the largest challenges to environmental management. The task of improving environments is mainly an effort to moderate summer heat and humidity and winter dryness as well as the range of moisture content that is created by the difference between them. Preservation metrics are most accurate and useful when based on a full year of data, which includes periods that are cool and dry as well as periods that are warm and humid.

Successful management of the environment for preservation requires a meaningful collaboration between collection care staff and facility managers. The storage environment is not something you fix, it is something that you manage.

In practice, the best environment you are able to achieve will be a balance between preservation quality, staff comfort, the ability of building envelopes and mechanical systems to modify the outdoor climate, and energy efficiency. The implementation of changes designed to improve preservation quality requires a process by which balanced and informed decisions can be made, with active participation from both collection care and facility management staff. In our experience, a willingness to understand the mechanical systems already in place, the ability to gather environmental data and compute the metrics, and the creation of a working forum where collections, preservation, and facilities staff all work together is the ideal approach.

This approach encourages a holistic view of the preservation environment that includes the varying needs of the collection and priorities for improvement, the capabilities of the mechanical system, and the broader functions and resources of the institution.

Future issues of IPI’s Climate Notes will provide in-depth information about preservation metrics, current research into issues of environment and preservation, why understanding dew point is essential, a range of preservation myths, the latest tools and technology, and much more.

Development of preservation metrics as well as other IPI technology for environmental assessment was made possible by grants from the Division of Preservation and Access of the National Endowment for the Humanities, the Institute of Museum and Library Services, and the Andrew W. Mellon Foundation.