The Role of Gelatin in Paper Permanence, Part II, Phase One: Gelatin as a Relative Humidity Buffer

Abstract

For over four decades, conservators and scientists have been interested in why papers produced in the 15th and 16th centuries have remained in much better condition than many modern papers. One factor, overlooked until recently, is the presence of gelatin as size in many early Western papers. Size was applied to finished sheets of paper in order to render them impervious to water and inks.

Recent studies, such as the groundbreaking work by Barrett and Mosier, have determined that "a positive correlation may exist between the present, good condition of historical papers and the amount of gelatin size they contain." In their study, Barrett and Mosier examine gelatin in relation to calcium content, pH and lightness of paper color in order to determine which combination of factors affects permanence. While their research suggests that pH, calcium content and gelatin content may work together to improve paper permanence, Barrett and Mosier state that "gelatin is an important component in the chemical and physical systems of paper...that deserves additional research attention" (Barrett and Mosier 1995).

As evidenced by Barrett and Mosier's conclusion, gelatin's role in promoting paper longevity is not well understood. It is known that amino acids of which gelatin is composed are able to buffer against the addition of both acidic and basic entities into paper. However, as Barrett and Mosier suggest, future work is needed on "temperature and humidity cycling to understand more fully the role of gelatin in paper stability" (Barrett and Mosier 1995).