Hi -

It's common knowledge to not place photos and documents on paper in
contact with glass or plexi.  Yet with polyester encapsulation documents
are placed in direct contact with the Mylar.

Why is this ok?  Polyester film, such as Mylar, is permeable to moisture
and there's also the recommended small gap in the seal.  So what protects
against mold growing where the film meets the document, and what prevents
transfer of image to the film?

In short, why is it ok for Mylar to touch the document and not ok for
Plexiglass?

- Stephen Linhart