Treatment of a Pope County Map
By Sherelyn Ogden
The director of the Pope County Historical Society recently contacted the Minnesota Historical Society's Manager of Outreach Services to enquire whether the Society would be interested in conserving a map of Pope County. The map had been hanging in the offices of a local business firm for what was believed to be decades. It was in very deteriorated condition and had seriously discolored. The firm offered the map to the Pope County Historical Society in exchange for a copy to display in its place. The Minnesota Historical Society did not appear to have a copy of the map, so the suggestion was made that we conserve the map in exchange for permission to make a copy for our collections.
The Society's map cataloger conducted a search of published sources and discovered that the Minnesota Historical Society did indeed have a copy of the map, which he located among our uncataloged maps. Our map was in better condition than Pope County's, but it was nonetheless in poor condition and needed considerable treatment before it could be used. The Society decided to conserve our own map instead of Pope County's and to provide copies of it to the Pope County Historical Society and the local business firm.
Map of Pope County Minnesota Compiled From Official Sources By W. J. Carson, Glenwood, Minnesota, is the complete title of the map. It measures 41 inches wide and 34.5 inches high. Although we are not certain of the date, we believe the map was produced about 1884. The call number is MAP 6F G4143.P7 G46 1884 .C27.
It was printed in black printing ink on a short-fiber, machine-made paper that had become dirty, weak, discolored, and acidic over time. Areas of the map were hand-colored in pink, blue, and yellow. These colors were, however, very difficult to discern because the surface of the map was extremely discolored. The front surface had been coated with shellac when the map was produced, a traditional technique of the time intended to protect the map in use and make it more durable. As the map aged and was exposed to light over a period of years, the shellac yellowed and darkened, making the surface very difficult to see. The map was lined with cloth, another traditional technique intended to provide strength. The cloth was filthy and detached in places. The map was broken into several pieces and suffered significant losses, especially along the edges. Extended portions of the printed border around the edge were missing.
The front surface of the map was cleaned with a vulcanized rubber eraser, a cleaning agent that is particularly suitable for the removal of grime. The cloth on the back of the map was removed by gently separating it by hand. The inks were tested for solubility, and the map was immersed in a bath of warm water containing a small amount of ammonium hydroxide. The shellac softened and began to float off the surface of the map. The bath water was changed several times until all the shellac, dirt and decomposition products were flushed from the paper. The water was drained from the map.
Because the map was weak and in pieces, reinforcement was necessary. Large loose pieces and small fragments were repositioned. Strips of Japanese tissue and wheat starch paste were used to hold the pieces in place. Then the back of the map was lined overall with Japanese tissue and wheat starch paste. Because the map was relatively large with major tears, an additional lining of cloth was needed to adequately support the paper. Light-weight, unbleached cotton muslin was adhered over the Japanese paper with wheat starch paste. The map was allowed to dry slowly under controlled pressure.
Following aqueous treatment and removal of the shellac, the map was considerably lighter, the hand-colors more visible, and the printing much easier to read. Archival-quality machine-made paper was toned to the color of the treated map. Losses were filled and toned to blend as needed. A photocopy was made of portions of the border and manipulated electronically to fit areas of loss. This image was copied onto the toned paper and inserted in the map so that all losses in the border were replaced.
At this point in the treatment the map was scanned by the Society's photo laboratory so we could have a digital image of the map as well as the original map itself. Scans were sold to the Pope County Historical Society and, from these, copies were made for that Society and for the local business firm. The original map was then encapsulated in polyester film, a clear, inert material that will protect the map in use.
This project was a collaborative effort on several levels. It involved two institutions and a local business firm. Staff from several departments of the Minnesota Historical Society worked together: outreach, processing, conservation, and photo services. Also, one of the Society's volunteers, a local retired conservator who is highly experienced in the treatment of maps of this type, guided the treatment. As a result of this rich collaboration, one of Minnesota's important artifacts has been preserved for use by current residents and future generations.