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Massachusetts Board of Library Commissioners Resource Guide Collection

Preservation in Massachusetts Libraries: Ensure Safe & Stable Storage

Subscribe and connect with Massachusetts Board of Library Commissioners (MBLC) Preservation Specialist Jessica Branco Colati and colleagues around the Commonwealth that work to advance the protection of cultural collections.


Note: We're renovating the Preservation in Massachusetts Libraries guide during Summer 2024. Please bear with us as we add, update, and reorganize MBLC's preservation resources.

Minimize risks, maximize safe space

A safe and stable storage space is the most important factor in the preservation of your special collections.

Safe - free from risks of damage, loss.

Stable - long-term viability, including room for growth

Minimize risks, maximize safe space

Manage Access

Minimize Theft, Vanadalism, Inadvertent Misplacement, & Loss. Lock up individual cases or rooms - create and clearly display any necessary access policies.

Mitigate Catasrophic Risks

Assess Risks. Monitor. Plan.

  • Flooding - Coastal, Riverine, Storm, Hydrostatic (floor)
  • Building Envelope Water Leaks - Roof damage, Icedams, Skylights, Windows, Doors
  • Plumbing and Equipment Failures / Leaks - Adjacent or Overhead - Water Supply Pipes, Sink / Toilet / Drain Backups, HVAC malfuncrtion (chiller leaks), Water / Steam Heating Pipe Leak or Bursting, Wet Pipe Fire Suppression Leak
  • Mold - Excessive humidities, temperatures, and air stagnation for extended periods
  • Fire - Adjacent electrical or heating equipment, particularly kitchens, without fire suppression tools or systems

Monitor Environmental Extremes

The following environmental impacts drive chemical and physical changes. Be sure to manage them in your collections spaces.

Temperature - Colder temperatures slow down natural chemical reactions of decay.

Humidity - High or low extremes in relative humidity (RH%) drive negative chemical and physical changes. High RH drives mold risk.

Light - Light exposure damage and fading, especially from UV light, is cumulative and irreversible.

Object Storage & Handling

Store objects in Appropriate Boxes & Enclosures

Clearly label the boxes / enclosures.

Stabilize, Isolate, or Fix Unstable Objects

Assess acute condition issues that risk further damage. For those, consider new strategies of isolation (restrict access), new enclosures, or conservation treatment.

Optimal environment for library collections?

You should optimize your collection's environment after you have minimized risks of severe or catastrophic losses -- such as those from from lack of security, flooding, mold, neglect, and repetetive damage from improper handling of popular objects.

What are the optimal environmental conditions for library collections? It can vary by format. But here are short, oversimplified answers:

  • Temperature: As cold as reasonably possilbe. Chemical decay of objects is slowest in cold storage environments.
  • Humidity: Moderate relative humidity (30-50%). Extremes can cause physical and chemical changes, and prolonged high humidities drive (potentially catasrophic) mold growth.
  • Light: As little light as possible. Fading caused by visible light and especially UV light is cumulative and irreversible.

Some of these standards are unreasonable for most libraries. But keeping these ideals in mind can be beneficial in how you manage their risks.

Current practices in temperature and humidity control for collections storage environments. Typically, in occupied spaces, temperature is around 70º F (±3º) and RH between 40%-50%. UV light blocked with window and flourscent bulb films.

Notice that all these targets accept small amounts of damage, so they should be understood as a balance between access, reasonableness, and preservation. These set point targets originally “emerged from a blend of human comfort needs, a limited amount of science, a considerable number of assumptions about possible damage from uncontrolled conditions, and an unfortunate tendency to generalize to a single rigid target." (Michalski, S. 2018, May 17. Agent of Deterioration: Incorrect Temperature. Canadian Conservation Institute.)

The current generally-accepted targets are actually currently under significant scrutiny and revision in the musuem community as institutions look for cost-savings and smaller energy footprints. For "smaller museums that never achieved such control anyway, the question becomes, where should it focus its temperature control efforts, and why?”" (Michalski, S. 2018, May 17.)

As you plan ways to optimize your collection environements for long-term preservation, consider the benefits of an environemtnal monitoring program. Not only can you gather data about the current environmental risk factors (Temp, RH, & Light), but you can identify and mititigate risks associated with improper environments that can be potentially catastrophic: mold growth, water damage, and pest infestation. Learn more about MBLC's free Environmental Monitoring Program (