Protocols for freezing collection materials - smith-special-collections/sc-documentation GitHub Wiki

Why to freeze collection materials

There are two possible reasons we would freeze collection materials:

To inactivate active mold
To kill insects

Freezing will not kill mold, but will put active mold into a suspended, inactive state. The materials may then be cleaned. This document covers only the freezing process, and does not include instructions for cleaning the mold once inactivated.

How to identify active mold

Active mold is soft and may smear when touched with a fine brush or similar object. Inactive mold is powdery, dry, and will seem to brush off materials, rather than smear.

Either active or inactive mold may give off a “musty” smell (though it is not recommended that you intentionally smell it up close).

How to identify silverfish

The insect we are most likely to encounter in incoming paper-based collection materials are silverfish. Silverfish thrive in warm, humid environments like attics and basements, in addition to bathrooms and kitchens.

Silverfish damage to paper is characterized by ragged, scraped-looking areas and irregular holes. They may also be present in fabric, and their presence can also be detected from their feces, which is described as pepper-like, that is, small, black, and visible to the naked eye, and yellowish stains.

What to freeze

If an incoming accession is found to have insects or signs of infestation in it, the entire accession (excepting any materials listed below under “what not to freeze”) should be frozen before it is transported to Neilson library.

Any collection materials found to have active mold on them can be frozen at the box-, folder- or item-level.

What not to freeze

The following types of materials should not be frozen, as they have been found to suffer damage from this treatment:

oil and acrylic paintings
photographic materials other than acetate film and modern photographic prints. For example, cased photographs (daguerreotypes, ambrotypes, tintypes) and glass archival materials including plates negatives, glass color transparencies (autochromes), lantern slides, mounted glass slides should not be frozen.
audio-visual items (other than film) including computer media (tapes, discs, optical), magnetic media (reel to reel, cassettes, VHS, Beta), audio grooved media (cylinders, discs)

How to freeze materials

If freezing to eliminate insects, allow the materials to come up to room temperature fully before freezing. This should be done in the quarantine room. This is particularly important during winter, when the materials may have gotten cold enough to allow insects to acclimatize to low temperatures during shipment.
Label the materials clearly with information about what accession or collection they are from, and if it’s less than a full box, what box the item or folder should be returned to after freezing. The label can be on the outside of a box, or on a piece of paper added to the outside of an item or folder.
If you are not going to be stacking multiple boxes on top of each other, consider leaving the lid off of any boxes to reduce insulation
Put materials in a plastic bag, remove as much air from the bag as possible, and seal the bag with the impulse sealer. Test the seal and add a second seal if needed.
Stack the materials in the freezer, leaving as much room for air circulation as possible.
Leave the materials in the freezer for a minimum of 72 hours and a maximum of one week. Check daily (except weekends) to ensure that the freezer maintains a consistent temperature at or near -40.
When materials are done freezing, remove them from the freezer and allow them to return to room temperature for at least 24 hours before you remove them from the plastic bags

How to document

Write a collection-level processing note that includes the following pieces of information:

What was frozen
Why it was frozen
How long it was frozen for
When it was frozen
What temperature it was frozen at