When the Geography and Map Division acquired an atlas commemorating the Marquis de Lafayette's 1824 visit to the United States, it gained a document that presented particularly vexing problems to the Conservation Division.
Paper loss, caused by mold, before and after treatment by the Conservation Division - Marita Clance
The maps are drawn with two types of inks with watercolor washes outlining the borders. They are on tracing paper, which is yellow with age. The use of this paper is unusual, and according to John Hébert, chief of the Geography and Map Division (G&M), the maps were traced. Mr. Hébert has identified an 1826 American atlas as the source for the map images. Each map is attached around its perimeter to a sheet of rag paper, presumably to support the delicate tracing paper and facilitate handling. Each map is folded in the center to fit the format of the atlas.
Their conservation presented a host of problems beyond those associated with caring for typical 19th century documents. Treatment of the mold damage was further complicated by the tracing paper. Old tracing papers are fragile, tear easily and distort with moisture. The translucency of the tracing paper is an important characteristic that can easily be altered during treatment. Early tracing papers were made by impregnating the paper with an agent such as gums or resins that allow light to pass through, unlike traditional paper that reflects light and appears opaque. Unfortunately, these agents eventually embrittle and discolor the paper, so few early examples have survived, making these maps even more rare.
Some time ago, water entered through the spine of the atlas and mold grew along the center fold of each map and support sheet. The mold caused dark stains, losses and altered translucency and consumed the paper hinges that once attached the maps in the atlas. The water caused the tracing paper to ripple and the iron gall ink (often acidic) to bleed into the paper, making it brittle and resulting in breaks and tears.
Water vapor from an ultrasonic humidifier helps to remove cockles from the paper. - Marita Clance
As part of the conservation process, Library conservators evaluated the maps to determine their physical and chemical stability. Photographs and a written report document the condition of each map. Tests were conducted to determine the best course of action. This treatment would be limited to mending the tears, reinforcing weakened areas, filling the losses, reducing the ripples and placing each map in a protective housing.
Temporary mends were applied over the embrittled ink areas to support them during treatment. An extremely sheer Japanese tissue coated with a cellulose ether adhesive was used throughout the project. It has an advantage over the customary wheat starch adhesive when working on tracing paper because it is made tacky with ethanol instead of water; it prevents mends from showing through the tracing paper, and it is easier to remove from fragile paper in the future.
The mold was loosened from the surface with a soft brush and gently captured in the small nozzle of a variable suction vacuum fitted with a HEPA. filter. This procedure was carried out in a fume hood, using a respirator and gloves to minimize any health risks associated with mold.
The maps were then separated from their paper supports for mending. The starch adhesive that joined them was softened by introducing water through Gore-tex fabric, best known for its use in waterproof rain wear. The advantage of using Gore-tex is that water is introduced into the paper slowly enough to soften the adhesive without wetting the paper. Once the maps were separated, all ink-damaged areas and tears were reinforced from the back with more sheer tissue mends, and the temporary mends over the front were removed.
One of the big problems of working on mold-damaged paper is that despite a few stains, the paper looks reasonably unaffected yet it disintegrates when touched. This is because mold consumes the interior of the cellulose fiber, leaving an empty shell that lacks mechanical strength. The mold-weakened areas were strengthened and the translucency of the paper restored with the application of warm water or dilute gelatin applied with a fine brush in tiny amounts to control expansion. The warm water seemed to regenerate the agent that made the paper translucent in the first place, and the gelatin also seemed to strengthen the paper. Gelatin has been used for centuries to size paper to give it strength. The affected areas were also reinforced from the back. Japanese tissue mends and losses were filled with a slightly heavier weight Japanese tissue toned with acrylic paint to match the surrounding paper.
Map before and after water vapor treatment. - Marita Clance
Unfortunately, regular methods of flattening paper did not eliminate the pronounced ripples, or cockles, in the maps. After some research, the cockles were successfully reduced by expanding the paper and allowing it to "stretch-dry." To do this, each map was placed on silicon-coated polyester film that has a slippery surface. Working on one quadrant at a time, the paper was humidified with water vapor generated by an ultrasonic humidifier that delivers a fine mist until the paper is sufficiently expanded. Light weights were then placed around the outer edges, and the cockles were gently pulled out as the paper dried. What makes this approach work so well is that the fine mist expands the paper slowly, giving the conservator a great deal of control. And the silicon-coated film allows the weights to glide as the paper dries, thereby preventing excessive strain on the delicate paper.
The support sheets were washed, given an alkaline reserve and mended with Japanese tissue and wheat starch paste. The flattened maps were then reattached to the supports using hinges of mending tissue around the perimeter.
Acid ink has embrittled the paper, causing it to tear. - Marita Clance
After conferring with the curator from G&M, it was decided that the fragile maps should be stored flat and not returned to their original bound format. This will facilitate use and their exhibition in the future. Each map is now protected in a mat structure made of preservation-quality board with clear polyester film over the opening for protection. The maps are stored together in a protective box with the original atlas cover. These maps were treated by senior paper conservators Linda Morenus, Ann Seibert, Sylvia Albro, Holly Krueger and this writer.
