Today I found a lovely insect nest to clean inside a document!
To clean something like this, the procedure goes from least aggressive to most aggressive – usually like this: first go over it with a soft brush to brush away any loose bits. Next, I take a microspatula and gently try to remove stuck-on bits from the surface of the paper. This is done with a magnifying device also, so that you can be very careful not to damage the paper. Each pass I make with the microspatula is followed by the brush to remove what is loose so that the view of the document is as clear as it can be for the next pass. The last step, after all is loosened and brushed away, is to take a soot sponge and go over the remaining staining and dirt that the microspatula can’t pick up. It is surprising how much dust and dirt remains and is picked up by this sponge. The staining of the paper and the damage the insect has done to it still remains, but many times it is enough to see the text underneath and make out the words, and will prevent any further damage.