Archival polyester film for encapsulation and conservation.

Archival polyester is an uncoated, untreated film with nothing added that could migrate into what it protects. Polymex® archival film is free from plasticisers, UV stabilisers, dyes and coatings, so it is chemically inert in contact with paper, photographs and textiles.

It is also dimensionally stable and very strong for its thickness, so it supports fragile items without stretching or sagging, and it stays crystal clear so the item can be read and photographed through it. Encapsulated in polyester, an item is protected from handling, dust, airborne pollutants and spills, and the film forms a barrier against acid migrating from neighbouring materials.

That is why polyester is preferred to PVC sleeves for long-term storage: PVC contains plasticisers that can migrate and damage collections over time.

In encapsulation, a document is placed between two sheets of polyester film cut a little larger than the item, and the film is sealed around the edges, usually by ultrasonic welding or with double-sided archival tape set back from the item. The document is held in place by the film and its own static, not by adhesive, so the process is reversible: cut the seal and the item comes out unchanged.

Because polyester carries a static charge, encapsulation is not recommended for items with loose, flaking or powdery media, such as pastel, charcoal or flaking paint. Paper is often cleaned and deacidified by a conservator before it is encapsulated. Encapsulated leaves can be bound together into an album-style post binding.