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Dirt: If the item is extremely dirty, the dirt can be "erased" with an eraser sponge from the preservation kit located in the mailboxes outside of Room 420 on the 4th floor and in Putnam. If you have a lot of material that needs erasing, consult the Collections Conservator, and determine with your team lead whether a student can do the work.
Specific formats often have their own preservation issues.
Bound volumes and scrapbooks
Photographs