Our POLYESTER SLEEVES are made from 2mil or 4mil archival polyester that has been approved by the Library of Congress for long-term storage. We use DuPont inert Melinex® or a suitable equivalent. This material has passed the Photo Activity Test (P.A.T.) which means that this material will not cause deterioration or harm to items stored in it.
Polyester is a sturdy, crystal clear material with a glass-like surface and archival properties that are approved by museums for indefinite storage (hundreds of years).