Most tears, particularly those alone the fold
lines, can be repaired by re-adhering the tear
with the use of non-acid archival tape on the back side of the poster. NOT
SCOTCH, MASKING OR ANY OTHER TYPE OF HOUSEHOLD TAPE.
We recommend an Archival Document Repair Tape
that is released by Lineco. It's easy to handle, non-acidic, can be removed,
and almost invisible. You don't normally use that much at a time so one box
usually last quite a while.
Unlimited has this item in stock if you don't have access to any.
For larger tears, a restorer should be used:
Here are LAMP Approved restorers: