Presented by Elissa O'Loughlin and Jayne Girod-Holt in February 1996 at the Washington Conservation Guild's annual "Three-Ring Circus" (simultaneous sessions on paper and textiles, objects and paintings). Reprinted with permission from the Washington Conservation Guild Newsletter, March 1996, p. 4-5.
In 1989, a collection of nineteenth-century ships' crew lists were discovered stuck to the bottom of a painted metal map drawer. The documents had been placed in the drawer without additional enclosures and were left largely undisturbed, until they were scheduled to be moved to a new location in the 1980s. Upon their discovery, the whole drawer was sent to the conservation lab; Elissa O'Loughlin, Senior Conservator, explored treatment options and Jayne Girod-Holt, a third year Winterthur intern at the Archives, helped carry out the treatment on two additional drawers that were found with the same problems.
Ms. O'Loughlin's research on the metal map drawers took her back to the construction of the Archives building on the 1930's. There was no information on the paint manufacturer, but research on contemporary materials and techniques indicated that the paint binder could be linseed oil, natural resin or cellulose nitrate (possibly with a final coat of shellac or cellulose nitrate), while the institutional green pigment was most likely iron-based. Solubility tests revealed that the paint was soluble in ethanol and acetone; it appeared stable in water at first but became blanched and soft after prolonged exposure. The paint was tentatively identified as cellulose nitrate binder with a cellulose nitrate or shellac coating.
Why were these particular documents stuck to just some of the drawers? It seems likely that the drawers may have been wiped with a solvent-containing cleaner just prior to storing the documents, or that the documents themselves had been exposed to a chemical such as ethylene oxide just prior to storage. The weight of a large stack of documents filling the drawer to capacity would have contributed to the problem of adhesion.
The key question was how to break the bond between the paint and the paper document. Because the paint was so readily soluble in alcohol and acetone, these solvents were avoided in treatment because of the risk of staining the paper. The media on the documents tested stable in water, so water applications were explored, including alkaline solutions and steam. Raising the pH had no appreciable effect on the paint and steaming caused skinning and delamination of the paper before the paint was affected. Immersion was also tested after first facing a scrap of a document with heat-set tissue. After two to three hours the heat-set tissue floated off but the paint had noticeably softened. A single- edge razor was used to pare the fragment away from the drawer with the paint still attached. The residual paint was then removed with a soft brush while the document was immersed in a second, smaller bath.
With these positive results, Ms. O'Loughlin decided to treat the embedded lists by submerging the drawers (with documents) in deionized water for a period of four to five hours. This was long enough to cause the paint to soften and loosen from the metal. The paint was detached with the aid of flat, chisel-edged tools cut for this purpose, and each document was removed with the paint still attached. A Plexiglas dowel was used to aid the removal: the document was gently rolled around the dowel as it released from the drawer and transferred to a bath of deionized water for brush cleaning. The curve of the dowel also helped to crack the paint residue on the document, aiding its removal. Any remaining stubborn paint flakes were left until after the document had dried overnight, and were then removed under the microscope with a scalpel. After removal the documents were deacidified in a magnesium bicarbonate bath, dried, and mended with Japanese paper and wheat starch paste.
There is some residual staining of the documents which appears to have been caused by their initial adhesion to the paint. The paint itself remained blanched on the drawers after drying. It was interesting to note that the heavily inked areas of the documents seem to have protected the paint; these areas remained darker, creating a shadow image of the document on the drawer bottom. The paint was more soluble in acetone and ethanol after immersion. It is possible that the water bath caused a component of the paint to leech out, leaving it brittle and more vulnerable to solvents.
Since the treatment began on the first drawer, 28 more have been located in the stack areas. This unusual problem is therefore more widespread than initially thought; the speakers invited suggestions from the audience that might speed up the treatment process; it was interesting to hear ideas from objects conservators, who were present because their session was canceled.