Abstract
Inert polyester sheets, such as Melinex and Mylar, are widely used in conservation to create envelope-like enclosures for storing and protecting flat objects (paper, parchment, papyrus, etc.). These materials are known to be chemically stable and present no direct risks to the enclosed items; however, as the films have a low permeability, such enclosures may lead to the creation of internal microenvironments. This will both limit the response to external changes and potentially trap any internally generated volatiles with the object. The likelihood of different forms of enclosures doing so is investigated in this paper. The resulting data will help to inform decisions about choices of construction of enclosures for particular objects, environments and purposes.