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#AskAConservator: freezing negatives

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"Film Negative Size Comparison - 35mm, 120, and 4x5" by Shawn Hoke is licensed under CC BY-NC-ND 2.0

CAPC is participating in #AskAConservator Day! Nick from Region of Peel Archives asks:

We’re looking to freeze a few thousand medium format film negatives from the 1940s and 1950s. Is it okay to house more than one negative in the same acid-free envelope, or does it have to be 1:1?

Photograph conservator Chloé Lucas answers:

For freezing, photographs should be housed following the Critical Moisture Indicator method, as follows:

  • Photograph is housed in an archival folder.
  • Approximately 2-3 cm of folders are placed in a Ziplock®️ type polyethylene bag,.
  • Each bag is sandwiched between two dried archival 4-ply matboard and placed in another Ziplock®️ type polyethylene bag, with a visual relative humidity indicator.
  • Packages are placed vertically in an archival box.
  • Box is wrapped in polyethylene (sealed with tape), with another visual relative humidity indicator.

It is preferable to have each photograph in a separate folder to protect the surface of the print or negative, in order to prevent the gelatin image layer swelling and blocking with another photograph in case of higher humidity or condensation.

However, it is possible to have several photographs in one envelope, to keep original grouping or to save space, provided the package is airtight.