Polyester is an excellent material for photographic storage in many ways; it is acid free, passes the silver-tarnish test, is inert, brilliantly clear, contains no plasticisers and will not crack or yellow with age, and is light and strong.
The cautionary notes are, firstly, that when using polyester for negative
storage one should avoid careless handling - kinking will raise ridges
in the surface which will not disappear, but remain to abrade the emulsion
surface if the negative is frequently accessed. Secondly, polyester
can build up a significant static charge, and to avoid the problem of
pulling in dust, an enclosed storage box should be used. In the case
of punched file sheets, the ringbinder boxes are ideal.
Many photographers now use polyester sleeves for prints as they used to use lamination, with the advantages that they are more transparent as a starter, and can be replaced when they become too scuffed with handling. A useful tip to make insertion of the print into the folder easier, is to use two folded pieces of paper acting as 'shoehorns'. Place one at both sides of the interior of the sleeve, and slide the print in. Then remove the paper guides. Saves a lot of aggravation, especially with glossy surfaced papers.