1 INTRODUCTION

ACIDITY HAS LONG BEEN RECOGNIZED as a major factor contributing to the deterioration of cellulose containing materials. In an effort to combat the harmful influence of acidity, investigators have developed a variety of deacidification techniques capable of decreasing the acid content of most works on paper that are to be found in museums and libraries.1 These techniques have been widely applied by conservators in the care of books and works of art on paper. However, deacidification is not advisable for all papers, and conservators are required to make judgments about whether to deacidify and in what way to deacidify each object entrusted to their care. In making these judgments, a myriad of factors must be considered, and in some cases insufficient information is available about the influence of deacidification to allow an informed judgment to be made.

The research conducted in our laboratory has been undertaken in an effort to add to our understanding of the influence of deacidification on paper-containing objects. We have not, of course, been able to address all of the questions that have been raised by the conservation community about deacidification. We have, however, begun to explore the fundamental reasons why deacidification decreases the rate of paper degradation.

The fundamental question asked in our research is: “Why is deacidification beneficial to paper?” The simplest answer is that deacidification neutralizes acids in paper, and acids have been known for nearly a century to be harmful to cellulose-containing materials.2 However, knowing that acids are harmful is not the same as understanding why acids accelerate aging or why deacidification increases paper stability. On the basis of the known chemical reactions of cellulose, it has been suggested that the aging of paper is a result of hydrolysis reactions and that acids catalyze the hydrolysis.3,4 However, recent publications have shown that an entirely different process, atmospheric oxidation, may also play a major role in the aging of some papers.5,6,7

The possible occurrence of both oxidative and hydrolytic processes in the aging of paper makes it difficult to predict the influence of deacidification. Although a decrease in acidity will decrease the rate of cellulose hydrolysis, the influence of pH on the oxidation of cellulose is poorly understood and differs for different oxidizing agents. For example, it is known that the oxidation of cellulose with hypochlorite is inhibited both by alkali and by acids.8 The influence of acidity on the oxidation processes that occur during the aging of paper has not been explored. The objective of the research described below was to determine this influence.