What is encapsulation?
Encapsulation is a technique developed
by the Library of Congress for the long-term preservation of rare and
valuable sheet documents.
It is done in two steps.
First the item is chemically stablized
and deacidified, and then it is sealed in an acid-free polyester enclosure.
The polyester (Mylar) capsule is a tough,
clear and attractive material that can withstand routine handling and
moving for many years.
The seal keeps the item dry and free of
contaminants, while the transparent polyester allows the paper to be viewed
from both sides.
The polyester capsule itself is not attached
to the paper in any way, and thus the poster can always be safely removed.
The only loss in the event of removal would be breakage of the seal, but
the unsealed capsule could still be reused as a protective sleeve.
It's like sticking your poster in a clear
envelope and it can still be framed.