3 THE KRAUS MAP HOUSINGS: CONSTRUCTING AN OVERSIZE SINK MAT

The 12 oversize maps in the H. P. Kraus Collection are all approximately 42 � 58 in. Most have several layers of paper and linings and are quite stiff; some are cockled. All have many previous mends and fills and are generally in a delicate condition. The housing described below protects the maps when stored and enables them to be safely carried.

The housing is a large sink mat with a cover hinged along one long edge. The mat forming the sink is constructed of Fome-cor. Our housings are 52 � 68 in., making the mat surround about 5 in. wide. The wide Fome-cor mat gives rigidity to the housing as well as creating the sink to protect the map. A laminate of two layers of Fome-cor was sufficient for eight of the maps. The remaining four are on wooden stretchers and required mats up to 1� in. deep; these were constructed of layers of Fome-cor and Tycore. The housing is held closed along the three open sides by linen ties. It is designed to lie flat in storage and when necessary to be carried by two people, upright with the hinge edge down. The map can be examined without removing it from the housing by leaning the cover down from a table or up against a wall, or folding it underneath the housing. As the versos of the maps generally contain no images or text, a photograph of the verso of each map is mounted inside the housing to discourage unnecessary handling of the map. The maps are not attached to the housing.

Coroplast, a corrugated polypropylene copolymer sheet, was chosen for the boards as it is inert, strong, lightweight, and inexpensive. Three disadvantages of this material are its relatively low melting point (230�F), the possibility of infestation in the small spaces of the corrugations, and the difficulty of attaching it to other materials. Alternative but more expensive materials include Gatorfoam and Tycore.

In three different instances it was necessary to attach other materials to the Coroplast. Ten point lignin-free board or cover weight paper was attached to the bottom board as a liner for the map to rest on. Even though the Coroplast we used contained an anti-static agent, there was still evidence of a static charge on the sheet and it was felt that a liner was necessary to protect the map. Rhoplex N-580 was used for this bond with qualified results. As the board was flexed, the lignin-free liner detached from the Coroplast and developed bubbles. If the entire housing were made at one time, flexing could be avoided. Using spot or edge adhesion might also avoid this problem. A spine hinge of paper-backed, cotton-linen book cloth was adhered to both boards with Rhoplex, and there were no problems with this bond when the Coroplast was prepared by sanding. There were many unsuccessful attempts to adhere the Fome-cor mats to the Coroplast. When Rhoplex was used and the board was flexed, the rigid Fome-cor separated from the Coroplast. BEVA (Berger ethylene vinyl acetate) was also tried, but solvent fumes were a problem. Hot-melt glue was suggested by the manufacturer, but it was difficult to apply a thin coat quickly over the large expanse of board. We were also concerned about the long-term stability of the hot-melt glue. Sewing the mats down with nylon monofilament was considered. Finally it was decided to attach the first of the two or more layers of Fome-cor to the Coroplast with album-type screw posts. Additional layers of Fome-cor were adhered with PVA [poly(vinyl acetate)], covering the screw posts.

The maps have been transported in these housings many times and shift very little as they are carried. Simple loop handles would make carrying easier.

This project was completed over a period of two years, working one afternoon a week. The project was designed by Patricia Ingram and work was supervised by staff, including Ingram and George Leake, but often done by inexperienced volunteers. The following instructions were written to reduce confusion resulting from such a fragmented schedule. The design is simply an ordinary sink mat enlarged, but when even a simple structure is enlarged, materials behave differently and procedure becomes even more important. Given the investment in materials and time an oversize housing project requires, one seeks to limit experimentation, and having a chronology of construction steps to begin with and improve upon can be useful.