Hermetically sealed encasements for historic document display and preservation

Abstract

The goal of this thesis was to develop designs and methods for the preservation and display of historic documents. The results were applied via the design, manufacture, and installation of five hermetic display encasements for the original Massachusetts Constitution (1780), a Goddard broadside of the Declaration of Independence (1777), an original copy of the Bill of Rights (1789), the 1629 Charter of Massachusetts Bay, and the 1692 Charter of the Province of Massachusetts Bay. In addition to meeting the aesthetic requirements for a permanent exhibit, the encasements had to have leak rates that would maintain less than 0.5 % oxygen content over 20 years and preserve 40 % relative humidity at 70 'F. Furthermore, the encasement portion of the project had a 300,000 USD total budget, approximately one tenth the budget allocated for the "Charters of Freedom" project at the National Archives. The encasements designed for this project incorporated a novel seal arrangement that "floats" the glass and allows for helium leak testingat any time, without disturbing the document. These design choices were motivated by developing a model for permeation of gases through a network of polymer seals. Preparing the preservation environment also required the design and fabrication of the "Moisturematic", a device that allows for controlled filling of a vessel with precisely humidified gas. Continuous monitoring of the atmosphere inside the encasements was made possible by the development of specialized instrumentation. In January 2009, these historic documents were put on permanent display in the Treasures Gallery at The Massachusetts Archives. Initial leak testing indicates that all encasement have preservation quality environments exceeding 20 years. In addition to design rules for developing high quality, relatively low cost environments for preservation, this thesis presents a roadmap for design of more generalized hermetic sealing and conditioned environments.