Exploring

Inherent Vice: Materials

Adhesives

The term adhesive refers to a compound that bonds one material to another. Adhesives are encountered in various types of paper-based collections, most commonly in book bindings, scrapbooks, documents that have been repaired, and photo albums. Adhesives can be natural (e.g., wheat starch paste) or synthetic (e.g., polyvinyl acetate); starch adhesives share common properties with cellulose, while synthetic adhesives are very similar to plastics.

Natural adhesives were first made from plant resins about 6,000 years ago. Later, animal, fish, and egg white-based adhesives were used. As modernization of adhesives continued during the 18th and 19th centuries, glues were made from various materials, including natural rubber and milk protein. Synthetic adhesives were developed in the early 20th century. Formulas for modern synthetic adhesives vary greatly, are often proprietary, and can change without notice.

Characteristic Types of Deterioration

The use of self-adhesive tape to repair tears causes staining.

Animal glues, traditionally used in bookbinding, break down over time, becoming discolored, dark, and brittle. They cause staining or simply crumble and fail. Synthetic adhesives react physically with water to produce swelling and chemically to produce structural weakening and acidic byproducts. In addition, evaporation of components within adhesives can cause them to become brittle.

Many adhesives used in collections in the past have not lasted well. Damage often includes discoloration, staining, and even failure of the adhesive, particularly in the cases of rubber cement and self-adhesive tape. While "archival" pressure-sensitive tapes that appear to be more stable than traditional pressure-sensitive tapes have been introduced, some problems have been observed with these tapes also. Natural adhesives such as wheat or rice starch paste are relatively stable and are often used in book and paper conservation.