Preservation and Access: Research and Development

Period of Performance

1/1/2019 - 12/31/2023

Funding Totals

$349,879.00 (approved)
$349,879.00 (awarded)

Encapsulation: Past, Present, and Future

FAIN: PR-263932-19

Johns Hopkins University (Baltimore, MD 21218-2608)
Patricia McGuiggan (Project Director: June 2018 to present)

A Tier II project to conduct experimental analyses on polyethylene-terephthalate (PET) encapsulation products used in preserving historical documents, along with the testing of newer encapsulation materials and the execution of a national survey about the number and condition of encapsulated documents in library and archival collections.

The preservation of documents by PET encapsulation is one of the most popular methods of paper conservation. In spite of this, there are concerns regarding whether the PET envelope traps acidic gases naturally produced by paper which might harm the document. We propose measuring the permeation of gases through archival PET as well as the properties of encapsulated papers. We will also survey the encapsulation methods used in libraries and archives in the US and test the condition of naturally aged PET in local libraries. We will also investigate newer, breathable films which might be used for archival storage of paper documents.

Media Coverage

Of Paper and Permeability (Media Coverage)
Author(s): Christen Brownlee
Publication: The Johns Hopkins Whiting School of Engineering Magazine
Date: 8/14/2018

Associated Products

The breathability of PET to water vapor: Thickness effects (Article)
Title: The breathability of PET to water vapor: Thickness effects
Author: Andrea K.I. Hall
Author: Molly K. McGath
Author: William D. Minter
Author: Patricia M. McGuiggan
Abstract: A model study of the permeation of water vapor through archival polyethylene terephthalate (PET) in the context of encapsulation is reported. Using intentionally wetted paper, the rate of mass loss of a wet, encapsulated paper was measured and found to be 1000 times slower than the rate of mass loss from wetted unencapsulated paper. The results show that water vapor can permeate through the PET film and the measured rate of vapor flux increases with decreasing PET thickness. The measured mass loss from the encapsulate was used to calculate the relative humidity (RH) inside the encapsulate and the moisture content of the encapsulated paper. The moisture content of encapsulated paper was calculated to be slighter higher than the moisture content of unencapsulated paper, which might be due to a modified cellulose network structure caused by the slower mass loss or variability in the paper, or due to condensation of water vapor on the PET within the encapsulate. The results of this paper quantify the movement of water vapor through PET film and provide conservators insight on the microenvironment in their PET enclosures.
Year: 2020
Primary URL:
Access Model: Subscription
Format: Journal
Periodical Title: Journal of the American Institute for Conservation
Publisher: American Institute for Conservation

Directional dependence of the mechanical properties of aged paper (Article)
Title: Directional dependence of the mechanical properties of aged paper
Author: Sophie Leheny
Author: Thomas C. Robbins
Author: Catherine K. Robbins
Author: Fangyi Zhou
Author: Andrea K.I.Hall
Author: Molly K. McGath
Author: Louise Pasternack
Author: Jay Wallace
Author: Thomas C. O'Connor
Author: Patricia M. McGuiggan
Abstract: Tensile testing
Year: 2021
Primary URL:
Access Model: subscription
Format: Journal
Periodical Title: Mechanics of Materials
Publisher: Elsevier

The Permeability of PET by Formic and Acetic Acid Vapors (Article)
Title: The Permeability of PET by Formic and Acetic Acid Vapors
Author: Patricia M. McGuiggan
Author: Andrea K.I. Hall
Author: Molly K. McGath
Author: Louise Pasternack
Abstract: The permeability of biaxially oriented polyethylene terephthalate, PET, to vapors from 5%, 30% and 100% formic acid solutions as well as the vapor from a 30% acetic acid solution was measured by gravimetric analysis in order to determine the transmission rate of the vapors through PET and ultimately understand the microenvironment that is created inside an encapsulate. The data shows that the permeation of formic acid vapor is at least two orders of magnitude slower than the permeation of water vapor. Measurements of the permeation of 30% acetic acid vapor through PET seemed to be due to the permeation of the water only, and the permeation of the acetic acid, if it occurred, occurred too slowly to be measured. The size of the diffusing molecule determines the permeation. Since the permeability decreases as the size of the diffusing vapor molecule increases, a plot of permeability versus vapor size allows the permeability of various other vapors through PET to be predicted. Colorimetry showed that porous PET allowed ambient vapors to diffuse into the encapsulate and the entire paper within the encapsulate was affected, not only the paper near the holes in the PET.
Year: 2022
Primary URL:
Access Model: subscription only
Format: Journal
Periodical Title: Studies in Conservation
Publisher: Routledge, Taylor & Francis Group