Cold Storage for Photographs: A guide for accessing photographs from cold storage

This guide should be followed when storing, handling, and accessing photographs and films placed into cold storage environments. Cold storage may be humidity controlled cold storage vaults, with or without an acclimation room, or non-humidity controlled vaults, refrigerators and freezers. Cold storage is defined in NARA 1571, Archival Storage Standards.

Cold storage is one of the best ways to slow deterioration of photographs, especially film-based photographs (negatives and positives). However, care must be taken to keep condensation from forming on items that are retrieved  from the cold and moved to a warmer environment such as a research room or designated holding area. 

Supplies needed for photographs stored in cold storage vaults

Depending on the type of storage vault or refrigerator, you should have the following supplies on hand:

• Clear plastic polyethylene or polypropylene bags with zipper-lock  closures or twist-ties, big enough for the item or box 
• Nitrile gloves
• Carts to move the photograph, film, or box

Accessing photographs from a humidity-controlled cold storage vault without an acclimatization room

• Handle gently – cold photographs and films are brittle and may be damaged by flexing. 
• Always wear nitrile gloves when handling individual photographs or films if the items are not in polyester sleeves. 
• Locate individual photographs, folders,  or boxes in the cold vault. Place the item(s) inside the clear plastic bag. Squeeze out the excess air from the plastic bag and seal the bag using the zipper-lock closure or a twist-tie. Do not use the bag if the zipper -lock seal does not work or if the bag has tears or holes. 
• Move the bagged photographs into a designated holding area. 
• Allow photographs to warm up slowly.
  • Small quantities of photographs will warm up faster than large groups or boxes. 
  • Warm up time to room temperature for less than five photographs: One  (1)  hour.  Photographs that are frozen may require more time to reach  room temperature.
  • Warm up time to room temperature for more than five photographs or a shoe-box: Four (4) hours.  Larger boxes may need to warm-up overnight.
  • Keep the plastic bag around the items until they feel at the same temperature as the surrounding room temperature. Never attempt to speed up warming of photographs by placing them near heat. 
• When bagged photographs or boxes no longer feel cool to the touch and are at room temperature, wipe off any moisture condensation on the bag prior to opening the bag to remove items.

Refiling photographs from office conditions to a humidity controlled cold vault

• Place unbagged photographs, film, or box inside the cold vault. 
• If the photographs are in a box, briefly open the box to let warmer air escape prior to reshelving. 
• Wear nitrile gloves as needed, and handle individual photographs carefully during refiling to avoid flexing other cold items that may be brittle.

Accessing photographs from a humidity-controlled cold storage vault with an acclimation room

Some cold vaults have an adjacent acclimation room  with a temperature and relative humidity that is between the cold vault setpoints and the research room or designated holding area setpoints. This means that bags are not needed in order to remove items from the cold vault as long as the following steps are followed:

Always use the acclimation room when entering and exiting a vault to minimize the influx of warm air and the resulting climate fluctuations in the vault. Open the outside acclimation room door and shut it completely before opening the vault door. 

The acclimation room climate is set at a temperature and relative humidity specific to the climate of the cold storage vault so that no moisture condensation will occur on materials when:

• Moving directly from the cold vault into the acclimation room; or,
• Once the items have warmed up to acclimation room conditions and then are moved to office conditions.
• Allow photographs to warm up slowly in the acclimation space
  • Small quantities of photographs will warm up faster than large groups or boxes. 
  • Warm up time to acclimation room temperature for less than five photographs: One (1) hour.
  • Warm up time to acclimation room temperature for one motion-picture reel: Eight (8) hours. 
  • Warm up time to acclimation room temperature for a shoe-box: Four (4) hours. Larger boxes may need to warm-up overnight.
• Photographs must warm up to the acclimation room temperature before moving the photographs to a research room or designated holding area because condensation could occur on the photograph. Also, plastic film is brittle at cold temperatures.

Accessing photographs from refrigerators, freezers or vaults without humidity control (where photographs are routinely stored sealed in airtight envelopes or bags)

• Photographs stored in stand-alone refrigerators, freezers, or non-humidity controlled storage vaults must be sealed for storage in heavyweight plastic bags or in special metallic foil/plastic barrier bags.  The National Park Service has a Conserve-O-Gram guide on how to pack photographs for these spaces. These types of cold storage appliances experience wide fluctuations in humidity during normal operation and when opened for access to the records. Humidity levels may fall below the levels recommended and cause extreme brittleness; or humidity levels can rise to the point where photographs become moist and allow mold to grow.
• Locate the wrapped package that you need to retrieve in the freezer and inspect it to ensure the package does not have tears or holes. If there are any tears, immediately place the package into a plastic bag and seal it.
• Move the wrapped package into a designated holding area.
• Allow the package to warm up slowly in the area
  • Warm up time to room temperature for a sealed package is Eight (8) hours to overnight. 
  • Keep the wrapping  on the package until the package feels the same temperature as the surrounding room temperature. Never attempt to speed up warming of photographs by placing them near heat. 
• When the sealed package  no longer feels cool to the touch, wipe off any moisture condensation on the outer bag prior to opening the packaging to remove photographs.
• Retain the packaging materials if possible to re-use when the item(s) are returned to the freezer.  Any torn or punctured bags should be replaced and new sealing tape should be used.
• Repackage the photographs following the guidance in step 1 and ensure an airtight seal before refiling. 

Precautions against Catastrophic Vault Failure

In some cases, photographs may be routinely bagged for cold storage as insurance against failure of the vault to retain the set temperature and relative humidity. Examples of possible failure include long-term power outages, a loss in climate control in which the temperature and/or relative humidity rises rapidly, frost accumulation, or water release. Bagging for storage is a wise precaution if the vault is unreliable in terms of climate control, where there are no backup power units or redundant climate control systems, or for extremely valuable photographs where any potential risk is considered unacceptable.

Precautions for Accessing/Refiling Records Taken to Offsite Locations

Records taken offsite should be placed in an insulated container, such as a small picnic cooler or chest, during transit. Insulated containers are available in a wide range of sizes from beverage size to several cubic feet in capacity. Insulated containers will prevent records being exposed to extreme weather conditions which could accelerate deterioration.

Records which were offsite should be allowed to acclimate to in-house office conditions before they are refiled to cold storage. This acclimation period should be either several days for single items or a week for boxes. This procedure is especially important where records might have been exposed to higher humidity levels at the offsite location.