Tuesday, June 22, 2010

Bulk Freezing

Although it's not cryogenics, freezing is a tool for archival preservation. Collection materials that are damaged by water in a disaster such as a flood or burst water pipe can be frozen to retard further deterioration. The frozen materials can then be thawed in small batches and treated. This is a job for preservation professionals, as you'll see from these leaflets about salvaging wet papers and wet photographs.

Freezing can also be used to eliminate insects and other pests from newly acquired collections. That's just what we did in December with a collection that had been stored in a barn. All magnetic media--audiotapes, videotapes, floppy disks--had to be removed first because they can be damaged by freezing. Each box of papers also had to be bagged in plastic, with excess air eliminated and the bag tightly sealed. By eliminating as much air as possible and freezing the materials very quickly, few ice crystals form. When the materials are gradually returned to room temperature while remaining in the bag, moisture condenses on the outside of the bag but not on the materials inside. This prevents any water damage to the materials that are frozen.

What I like about this use of freezing is the mass-treatment approach. Five pallets of boxed papers received preservation treatment as a big group--that's a cost-effective process! This is the way archivists approach many aspects of our work. It's when we have to deal with items individually, be it applying intensive conservation treatments to each or describing every single document individually, that our systems break down and our backlog grows exponentially. In archival work, we're always looking for an aggregate approach.

Supplies were at the ready as we prepared an archival collection for freezing.

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