Topics in Photographic Preservation 1997, Volume 7, Article 11 (pp. 88-90)
The merits of methyl cellulose, one of the most stable cellulose ethers, have been extensively discussed during past years.1 A material with excellent aging characteristics, it has been found suitable for a variety of paper conservation treatments, among them, to name only some important ones, aqueous lining, sizing, consolidation, poulticing and temporarily supporting paper objects.2 Especially as a lining adhesive, used separately or in mixture with wheat starch paste, methyl cellulose offers several advantages over the exclusive use of wheat starch paste. It allows the adjustment of the working properties of the wet adhesive and, more significantly, forms a discrete, flexible film upon drying. Unlike a dried wheat starch paste film of comparable thickness, it is almost free of distortions and contraction, and is easily reversible with only a moderate application of moisture. These useful properties make methyl cellulose ideal for one type of lining technique discussed here, the so-called remoistenable backing. The idea of preparing lining papers in advance of treatment by coating them with an adhesive film that is dried and later remoistened evidently was first experimented with in the 1980s by Bob Futernick, and was further developed by Cathy Baker. Her short, explanatory article appeared in 1990 in the Paper Conservation News.3 Since that time, however, no update has been given on this lining method which offers an interesting alternative to other backing techniques aimed at reducing the amount of moisture contacting the object during treatment (so-called "dry" linings). In most of these treatments, the wetness and bulk of starch- or other water-based adhesives is adjusted during the lining treatment and before the pasted paper touches the object. Remoistenable linings allow even greater control over these crucial parameters and are therefore suitable for the treatment of particularly moisture-sensitive objects. The lining technique has been used on a variety of objects including drawings on fragile papers and planographic prints, and on crayon enlargements. In a series of experimlinings have been used for the support of unmounted, curled albumen prints.4
The thickness of the adhesive layer can be adjusted by varying the concentration and composition of the mixture, and by choosing an appropriate screening material. The weave of Pecap (76-T), for example, is comparatively fine and thin, and therefore produces a more discrete adhesive layer than the coarser structure of generic window fly screens, which can be used alternatively.
By modifying the amount of moisture applied to the dried adhesive film, the degree of adhesive tackiness or activation can be adjusted. Under all circumstances, however, the adhesive layer has to be moistened evenly to ensure its uniform attachment to the object. If the remoistening step is carried out unevenly or excessively, the adhesive will penetrate the lining paper further than during the initial preparation, which can result in a mottled pattern on the reverse of the lined object.
Aside from a variety of kozo papers and tissues, gampi paper has been used for the remoistenable lining of distorted objects (e.g. tracing papers) to counteract their tendency to curl.
Remoistenable linings are probably most useful for the support of moderately-sized objects and for objects that are returned to relatively stable climate conditions. First, the lining steps have to be carried out swiftly which can be more easily accomplished with objects that allow relatively easy handling. Second, a remoistenable lining may not support large or heavy objects because the bond between the remoistened adhesive and the object may not be strong enough. Third, the lining is relatively easily reversed due to the hygroscopicity of methyl cellulose, and should not be used for supporting objects that will be stored under very humid storage conditions.
Art Conservation Department
Rockwell Hall 230
Buffalo State College
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Buffalo, NY 14222
1 R. Feller et al., Evaluation of Cellulose Ethers for Conservation, The Getty Conservation Institute, 1990. C. Baker, "Methylcellulose and Sodium Carboxymethylcellulose: An Evaluation for Use in Paper Conservation Through Accelerated Aging”, Adhesives and Consolidants -IIC Paris Congress Preprints, N.S. Bromelle et al., eds., London, England, IIC, 1984: 55–59. Jirina Strnadova and Michael Durovic, “The Cellulose Ethers in Paper Conservation”, Restaurator, 15 (1994): 220–241.
2 C. Smith et al., compilers, “Adhesives”, Paper Conservation Catalog, The Book and Paper Group, AIC: 103.
3 C. Baker, “Polyester Screening Material: Uses in the Paper Conservation Lab”, Paper Conservation News, 55, (Sept. 1990): 11.
4 Unpublished student project carried out by Lee Ann Daffner, Art Conservation Department, Buffalo State College, 1993. The idea of testing the application of this lining method on albumen photographs grew out of Paul Messier's research, “Work in Progress: An Analysis of the Effect of Water on the Cracking of Albumen Photographs”, Topics in Photographic Preservation, Photographic Materials Group, AIC, 1991: 170–178.