1 INTRODUCTION

Enzymes are often used in paper conservation to aid in the removal of adhesive residues from previous repairs or to facilitate removal of poor-quality secondary backing supports and mats.1 It is often necessary to remove these materials from paper artifacts because they may contribute to the deterioration of the paper as they age, or it may be desirable to return the object to its original format. In many cases, these extraneous materials cannot be safely removed by mechanical means, and the use of enzymes is required. The enzyme amylase is used to remove starch-based substrates such as pastes. Proteases and trypsins are used to remove protein-based substrates such as animal glues, gelatin, and casein.2 Various rinsing procedures are employed to remove the enzymes after treatment. It is important to reduce their quantity as much as possible because it is not known whether they may also be harmful if allowed to remain in the paper.

The major thrust of research previously undertaken has focused on the application and use of various types of enzymes for treatment of artifacts in paper and painting conservation. The general procedure following an enzyme treatment has been to rinse the paper with room temperature water. In addition, some conservators employ an alcohol or hot water rinse in an attempt to denature any residual enzymes. Quantitative analysis has not yet been undertaken to determine the extent to which enzymes are removed from paper artifacts by rinsing alone. The aim of our research was to establish whether enzymes are in fact removed from paper after rinsing with water. The procedure involved tagging the enzymes with the radioactive iodine isotope, iodine 125, and determining if any radioactive enzyme was left in the paper after rinsing.