Just like museums and galleries, archives and libraries must pay close attention to the temperature and humidity conditions in their spaces. It would be tempting to think or expect that archive collections are not as materially diverse as ethnographic museum collections given that the first thing that may come to your mind when you think “archives” is paper. However, this would not be entirely accurate. For example, it would not be strange to find the following materials requiring carefully monitored archive temperature and humidity conditions:
- Paper and cardboard of different times and component materials (cotton, wood pulp)
- Parchment and leather or textile materials on bound books.
- Wax (seals)
- Metal (clips, bindings, applications)
- Dyes, pigments and resins (in illuminated manuscripts, for example)
- Photographic materials (early plastics, gelatin, modern prints, etc.)
Preserving the invaluable treasures housed within archives and libraries requires meticulous attention to environmental conditions. Among the many factors impacting the longevity of archival materials, temperature and humidity stand out as crucial elements. So, what environmental conditions are recommended for archival materials and how can you keep track of them?
Understanding ideal archive temperature ranges
Maintaining a stable temperature can be paramount in safeguarding archival materials from deterioration. According to the Society of American Archivists (SAA), the recommended temperature range for archive storage falls between 60°F to 70°F (16°C to 21°C), with emphasis on minimizing fluctuations. This range strikes a balance between mitigating the risk of mold growth in warmer conditions and preventing the brittleness caused by freezing temperatures. It also aligns with the traditional 50%-70F recommendations, although we recommend looking into these numbers a bit more before you make any decisions as there are many considerations to make depending on your region and what your building is capable of. The Smithsonian Institution Archives, for example, shares a variety of temperature settings used depending on the material stored in each particular space:
The recommended environmental standard for paper-based collections is 35-65°F and 30-50 percent relative humidity (RH). However, different materials may require different standards… Glass negatives, color photographic prints, compact discs (CDs), and magnetic video tapes are stored at 52°F (11°C) and 30 percent RH. Film-based materials, such as reels and still image negatives, are stored at 26°F (-3°C) and 30 percent RH. In addition to the storage at SISC, the Archives also has an on-site freezer for frequently accessed microfilm collections, and for the treatment of pests found in collections. The freezer is maintained at 18°F (-8°C).
Beyond maximums and minimums, why does the SAA recommend that fluctuations be minimized to remain within the suggested ranges? Consistency is key; fluctuations in temperature can accelerate chemical reactions within materials, hastening their degradation. For delicate items such as photographs and film, adherence to the lower end of the temperature spectrum is advisable to minimize the risk of fading and emulsion damage. For articles with mixed material composition, we must keep in mind that temperature changes will affect each material differently. Each material will expand and contract at different rates. If they are all together on the same object, this can cause component parts to pull away from each other and either warp or break up the object.
Thinking about levels and fluctuations can be complicated if you are running your environmental monitoring on Excel, so make sure you look into your monitoring software options. Conserv Cloud, for example, lets you input your desired minimum and maximum setpoints for different areas (and seasons of the year), and then shows them as green bands in your graphs so you can easily tell whether your spaces are within your desired ranges or not.
Balancing archive humidity levels
In some ways, humidity control is equally, if not more, crucial in preserving the integrity of archival collections. For example, the American Library Association (ALA) recommends maintaining a relative humidity (RH) level between 30% to 50% for photographic materials, although this does not necessarily extend to all other materials in an archival collection. In the case of photographs, this range helps prevent the absorption of moisture by hygroscopic materials, such as paper, which can lead to swelling, warping, and mold growth.
Excessive humidity can be particularly detrimental, fostering the proliferation of mold and mildew while accelerating chemical deterioration and even increasing the reproduction of certain humidity-loving pests like silverfish. Conversely, overly dry conditions can cause materials to become brittle and prone to cracking. Employing a reliable HVAC system equipped with humidity sensors and dehumidification capabilities is essential for achieving and maintaining optimal RH levels. If you are running a very small archive or library, and HVAC systems are not available to you, check out some of the conversations in the Conserv Community of different colleagues requesting de/humidification equipment recommendations.
Some of our users in small institutions have mentioned that even putting out buckets of water in spaces that get extremely dry during certain times of the year is enough to bring their relative humidity readings to less extreme levels. Being able to monitor the effect of these buckets in real time helps them avoid losing control of this low-tech humidification solution.
Impact of environmental factors
Various external factors can influence temperature and humidity levels within archival storage spaces. Factors such as building location, building materials and impermeability, and HVAC systems can all impact environmental stability. Proximity to sources of heat or moisture, such as windows, plumbing fixtures, and exterior walls, can introduce fluctuations in temperature and humidity, necessitating strategic placement of materials and monitoring equipment.
Furthermore, seasonal changes and regional climates must be taken into account when designing archival storage facilities and implementing environmental control measures and setpoints. Collaboration with HVAC specialists and preventive conservation experts can help mitigate the impact of these external factors, ensuring the long-term preservation of archival materials. Remember to evaluate your own spaces so you can define your own, realistic environmental monitoring goals.
Monitoring and maintenance protocols
Regular monitoring of temperature and humidity levels is essential to detect deviations from optimal conditions promptly. Automated monitoring systems equipped with alarms can provide real-time alerts, enabling prompt intervention in the event of HVAC malfunctions or environmental fluctuations. Whether you are in museums or library and archive settings, active environmental monitoring is key to reducing or even entirely preventing costly disasters.
In addition to automated systems, periodic manual checks can also be conducted using calibrated hygrometers and spot checkers. These checks serve as a supplementary measure to verify the accuracy of automated systems and detect localized environmental anomalies. Remember your data loggers are giving you a general reading for a space but may not necessarily be picking up on small microclimates.
If you are not sure about how to start a monitoring program, download our free Definitive Guide to Environmental Monitoring, which outlines the most important steps to setting up a successful environmental monitoring program in a heritage institution.
Implementing remedial measures
In the event of environmental fluctuations or HVAC failures, swift action is imperative to mitigate potential damage to both archival materials and infrastructure. Affected collections can cause more headaches than you’d expect. Not only are the collections themselves out of circulation, but you may have to close down entire affected areas to the public, change your working offices, and in worst case scenarios, throw out collection items and refurbish the whole area.
Establishing contingency plans and protocols for responding to emergencies, such as power outages or equipment malfunctions, is essential to minimize the risk of irreversible damage. Make sure you check out dplan.org if you need help creating or updating your disaster plan.
Even temporary measures taken promptly, such as deploying portable HVAC units or dehumidifiers, can help stabilize environmental conditions and stop a situation from getting worse until permanent repairs are undertaken. Communication and coordination among staff members, facilities personnel, and conservation experts are critical in executing timely and effective remedial measures. Don’t miss the upcoming webinar (Feb 29th, 2024) by Connecting to Collections (C2C) Care where our preventive conservator, Melissa King and facilities expert Christopher Cameron, will address the topic of Working with Facilities to Create a Fuller Picture of Your Collection Environment. If you miss it, there is probably a recording to watch on the C2C Care website!
Conclusions
Maintaining optimal temperature and humidity levels is fundamental to the preservation of archival materials. By setting and adhering to your own guidelines and implementing robust monitoring and maintenance protocols, collections care professionals working in archives can safeguard these invaluable documents for present and future generations.
Collaboration with other team members in the organization such as conservators and facility managers is essential to achieve any long-term preservation goals. It’s important not to take set number recommendations for archive temperature and humidity levels as if they were set in stone. Generally speaking, materials tend to be resilient and are used to their storage environments, so it’s more important to avoid extremes and be aware of what constitutes normality in your own spaces.
By following these recommendations, remaining vigilant, and engaging in active environmental monitoring as opposed to passive environmental data collection, collections care professionals can uphold the integrity of archival materials and contribute to the ongoing preservation efforts within the cultural heritage sector.
If you have any questions about environmental monitoring, integrated pest management, or just want to talk about preventative conservation, please reach out to us! Don’t forget to check out our blog or join our community of collections care professionals where you can discuss hot topics, connect with your peers or even take a course to get familiar with the Conserv platform.
