Volume 46, Issue 3

A survey of the document preservation technique referred to as encapsulation was conducted of United States institutions with catalogued archives and paper collections. The purpose of this survey was to inform: an estimation of the proportion and type of materials and documents encapsulated, the popularity of various methods and the materials used for encapsulation creation, and the condition of encapsulation materials and encapsulants in collections. The survey responses provided the first data pertaining to the state of encapsulation approximately fifty years after encapsulation for preservation was formally developed. Survey results suggest that: encapsulation is well-established and highly valued in the toolbox of preservation strategies yielded by conservators and collection managers; that most encapsulation construction materials used during the past fifty years evidence few deterioration problems such as yellowing or embrittlement; that it is not a frequent occurrence that conservation treatments like deacidification, washing or the introduction of pollution sorbents is common; and that there is general satisfaction with encapsulation as a preservation method for weakened paper, maps and posters, whether the encapsulation is used in an archival or exhibition environment. Several text responses from survey participants expressed that future research on polymeric material stability and permeability may alleviate some concerns regarding future use of encapsulation.

Permeability is broadly defined as the ability of a material to allow the transportation of liquids, gases, or vapors through it. Although numerous references can be found in the literature giving the permeability values of polymers, there is no standard unit of gas or vapor transport, making comparisons difficult. This review summarizes the permeability of single polymer films used in book and paper conservation, specifically addressing the permeability of storage materials and processes such as encapsulation. In particular, the permeability of the polymer films to oxygen, nitrogen, hydrogen sulfide, water vapor, and acetic acid is summarized. The permeability was found to differ by over 7 orders of magnitude when comparing different gases and vapors diffusing through the polymer films. The permeability is dependent on the molecular size of the diffusing gas or vapor, with smaller molecules diffusing faster than larger molecules. In addition, the chemistry of the film plays a role. Hydrophilic polymers have a much greater permeability of polar diffusants such as water vapor than hydrophobic polymers. In addition, the permeation increases significantly with temperature. The review provides data of the permeability properties of the films used by conservators and will enable them to make an informed decision of the best material for their application.

In this study, an alternative method for non-aqueous and non-alcoholic lining of paper documents is proposed, with Japanese tissue paper pre-coated with polyvinyl butyral (Butvar® B-76) adhesive used as the lining material. The adhesive layer is activated with a solvent mixture of dimethyl carbonate and n -hexane. The findings of the conducted tests indicate that the proposed method is safe with regard to the tested writing and printing media. Furthermore, it does not alter the paper structure or cause any deformation of the folios. In order to evaluate the effectiveness of the lining and the ageing characteristics of the pre-coated tissue, the mechanical properties of the lined samples, their colour stability, the pH values of the aqueous extracts and the removability of the lining tissue were tested both before and after accelerated degradation. The results were considered satisfactory.