THE LAMINATION OF DOCUMENTS

Paper consists essentially of cellulose and, as such, is susceptible to deterioration when exposed to adverse conditions such as high relative humidity, which encourages mould growth of cellulytic organisms, and acidity, which causes hydrolytic breakdown of the cellulose molecules. This type of degradation causes a loss of mechanical strength with the result that paper becomes brittle and fragile. It is, moreover, an irreversible process so that the intrinsic strength of paper cannot be restored by any known means, and, therefore, some form of lamination will have to be adopted in which the fragile paper documents are sandwiched between two sheets of a supporting material. The classical method of lamination is that of ‘silking’—a process in which both sides of the document are covered with fine silk having an open weave which is attached by an adhesive such as starch paste or dextrin. This process has been used for a long time for the repair of valuable books and manuscripts, but it does suffer from the disadvantage that deterioration of the silk will inevitably occur unless care is taken in the choice of the quality of the silk and of the adhesive, and also the conditions of storage must be carefully controlled.