Volume 6, Number 1
Feb 1982

Soluble Nylon Reevaluated

First mentioned in the conservation literature in 1958, soluble nylon (N-methoxymethyl nylon, sold under the name of Calaton CB by ICI) has been used as a consolidant for a variety of materials, including paper, textiles, stone, wood, wall paintings and feathers. In a recent article entitled "The Case Against Using Soluble Nylon in Conservation Work," Catherine Sease discusses its chemical structure, properties and behavior and reviews its 23-year history of use in conservation. Her experience in working on objects treated with the resin leads her to recommend that soluble nylon not be used for conservation purposes.

"Soluble nylon was advocated for conservation use because it had the following desirable properties: 1) flexibility; 2) a clear matt appearance; 3) it exerts no undue contractile forces; 4) good adhesive properties; 5) permeability to water vapor. Experience with a large number of objects made of widely differing materials that were treated with soluble nylon as long ago as the late 1950s and early 1960s has shown that, without exception, all of them exhibited the same problems: 1) the film had attracted dirt and dust, badly discoloring the objects and obscuring painted decoration; 2) the film was not matt; 3) the film had exerted strong contractile forces, peeling off the surface of the object with it; 4) the film was no longer flexible; and 5) the film was insoluble. Of the desirable properties originally claimed for it, permeability to water is the only one that seems to be maintained over time. . .

"There are so many other more suitable resins and materials now available which exhibit none of the undesirable qualities of soluble nylon that a replacement should not be difficult to find. For example, friable objects needing consolidation before soaking for soluble salts have been successfully treated with [Acryloid] B72 (a methyl methacrylate/ethyl acrylate copolymer manufactured by Rohm and Haas, Philadelphia, Pa.) which has not notice ably slowed down or impeded the movement of salts. More over, it has not discolored, attracted dirt or become in soluble. It can only be concluded that soluble nylon should no longer be considered a suitable material for conservation purposes."

This article was published in Studies in Conservation 26: 102-110, 1981. Studies in Conservation is published by the International Institute for Conservation of Historic and Artistic Works, 6 Buckingham St., London WC2N 6BA. The author is currently at the Metropolitan Museum of Art.

A related article in the 1980 Preprints of the American Institute for Conservation meeting in San Francisco reviews and evaluates consolidants for paint (which are often useful in book and paper conservation as well): "A Consolidation Treatment for Powdery Matte Paint." The author, Elizabeth C. Welsh, was at the Metropolitan Museum of Art at the time. She describes ten different paint consolidants or types of consolidant, and reports her systematic tests which enabled her to choose between the two that gave best results, Acryloid B-72 and polyvinyl acetate. By using different solvents for each consolidant, she got ten test areas on a painted panel, which she evaluated for appearance and quality of consolidation. Acryloid B-72 was chosen as the beat, in the slow-drying solvent diethylbenzene, which is in the same family as toluene and xylene but less hazardous.

Acryloid B-72, as well as polyvinyl acetate, soluble nylon, other consolidants, and a number of solvents, are sold both by Conservation Materials (340 Freeport Blvd., Box 2884, Sparks, NV 89431, tel. 702-331-0582) and Talas 130 Fifth Ave., New York, NY 10011, tel. 212-675-0718).

"'Acryloid B-72" is the trade name used by the manufacturer, Rohm and Haas Company, in America. In England it is known as "Paraloid B-72" and in Germany it has yet another name. It is sold as a granulated solid or in a concentrated solution.