JAIC 1997, Volume 36, Number 3, Article 8 (pp. 253 to 261)
JAIC online
Journal of the American Institute for Conservation
JAIC 1997, Volume 36, Number 3, Article 8 (pp. 253 to 261)




  1. Make an exact paper template of each map. Using the template instead of the map during the construction of the housing reduces damage to the map caused by handling.
  2. Adhere a lignin-free liner to the Coroplast. If the Coroplast is not precut, cut an upper and lower board to desired size with a utility knife.Cut a rectangular liner of 10 point lignin-free board or cover weight paper to a size several inches larger than the map template.Center the liner on one of the Coroplast boards, and outline the corners of the liner with pencil on the Coroplast to aid in placing the glued surface down accurately (fig. 2).Apply Rhoplex to the underside of the liner, and adhere to the Coroplast board. Rhoplex is very sticky and will bond on contact; avoid allowing the free end of the liner to touch the Coroplast.
  3. Seal or fill the ends of the corrugated boards with PVA or hot-melt glue to discourage infestation.
  4. Punch holes, and secure ties. Measure and mark positions for ties on three sides of the Coroplast boards. Be generous in deciding the number of ties, as snug closure is essential for safe transportation (fig. 3).Use a chisel and hammer to make slits in the Coroplast for each tie. Slits should be at least in. from and parallel to the edge.Pass a 12 in. length of linen tape through each slit and sew as illustrated, creating a snug loop attachment to the Coroplast. Cut the end of the tape at an angle to prevent fraying (fig. 4).
  5. Sand the spine edges of the Coroplast to prepare the surface for attachment of the inner and outer hinges. Draw a pencil line 3 in. from the spine edge (the edge with no ties) on the top and bottom surfaces of each Coroplast board. This line marks off four areas where adhesive will be applied to attach the hinges.Use an electric sander to sand these areas, roughing up the smooth surface of the Coroplast.
  6. Attach the outer hinge. Cut a strip of book cloth with the grain long. This strip will be the outer hinge and should be 8 in. longer than the spine edge of the Coroplast. The width of the strip should be 7 in. plus the thickness of the spine. The spine thickness is equal to the total thickness of the Fome-cor mats plus two pieces of Coroplast plus 4 pieces of book cloth plus 1 piece of book cloth for ease.Set dividers to the spine thickness.Fold the hinge in half at each end and pinch it, creating two small creases as shown in figure 5.Using the crease in the end as a guide, mark the thickness of the spine with two pencil marks in the center of each end of the hinge, as shown in figure 5.Draw two pencil lines along the length of the hinge connecting the pencil marks and outlining the spine area of the hinge.Position the two pieces of Coroplast and the hinge, paper side up, as shown in figure 6.Apply Rhoplex to the hinge using rollers.Move the Coroplast covers onto the hinge, aligning the edge of the Coroplast with the nearest pencil mark and leaving an equal cloth turn-in at each end of the spine. Press down on the Coroplast to ensure adhesion of the hinge.Turn in the ends of the cloth hinge, adhering it to the upper surface of the Coroplast. Pull the sides of this turn-in toward the center, gathering extra cloth in the spine area. Bone the cloth down onto the Coroplast.Use scissors to make two relief cuts in the spine area of each turn-in, as shown in figure 7. Do not cut all the way to the fold of the cloth. There should be at least in. of uncut material at the folded edge of the cloth. Bone down the cloth in the spine area.Close the housing, and bone down the cloth on both outer surfaces.
  7. Attach the inner hinge. Cut another hinge of book cloth with the grain long. This strip will be the inner hinge and should be in. shorter than the spine edge of the Coroplast. The width is the same as that of the outer hinge.Crease the ends of the hinge, and outline the spine area of the hinge, as described in steps 6 c–e.Make two folds along the pencil lines with the paper side of the cloth to the outside, as shown in figure 8.With the housing open, use a piece of scrap board to apply a generous amount of adhesive to the paper surface of the outside hinge between the edges of the Coroplast.Use a bone folder with a rounded edge and your hands to place the folded inner hinge, paper side down, onto the glued area. This is best done one fold at a time, by pinching the cloth of the inner hinge together at one fold and setting that fold in place at the edge of the Coroplast. Bone this fold down on the cloth side, working across the spine area to the other fold (see fig. 9). The inside hinge tends to pull away from the edges as it is adhered (see fig. 10).Once the spine is adhered, fold both hinge flaps to one side, place scrap paper between the flaps, and apply adhesive to the paper surface now exposed. Adhere this cloth to the adjacent sanded area of Coroplast, and bone it down. Repeat for the other hinge flap.Remove any excess Rhoplex with a vinyl eraser.
  8. Cut Fome-cor mats. If the shorter dimension of the map exceeds 40 in., the Fome-cor mat will have to be pieced. The map should fit in the sink with as little extra room as possible to minimize shifting of the map when the housing must be turned on edge for transporting. The surround of the mat should be wide enough to give rigidity to the housing. Cut a Fome-cor sheet to the size of the base of the housing using a utility knife.Center the map template on the Fome-cor, and secure with weights.Long straightedges are useful in creating a rectangular window around the irregularly shaped maps. Once the appropriate window is achieved, mark the Fome-cor at the corners of the window. We allowed 3⅙ in. leeway around the map.To avoid future confusion, label each layer of the Fome-cor mat on the edge adjacent to the hinge with each of the following: north;upper mat or lower mat (if there are more than two layers, label accordingly);top or bottom surface (keeping the orientation of each layer the same in gluing as in cutting helps in achieving a clean window).Cut out the sink using a utility knife with a fresh blade. Make clean, vertical cuts. Polystyrene foam dulls blades quickly, and the snap-off blade of the Olfa knife was convenient here.Check the fit with the map template.Cut another layer of Fome-cor to the size of the base of the housing, and place this layer beneath the cut mat. If mats are pieced, stagger the joins, as shown in figure 11.Trace the inside edge of the cut mat onto the Fome-cor beneath it with a pencil. Pencil marks on this edge will later be covered with paper.Cut lower mat pieces, and label as described in step 8d. If there are more than two layers of Fome-cor, use the same mat as the pattern for all the others.
  9. Attach the lower Fome-cor mat to the Coroplast with screw posts. Position the lower Fome-cor mat on the Coroplast base, and secure with weights.Cut a jig for quick marking of holes. Use the jig to mark locations for holes at least in. from all edges as shown in figure 12. We put a screw post every 6 in., but fewer could be used. Where the ends of pieced mats join, put holes at all corners.Punch with an awl or drill holes through the Fome-cor and the Coroplast at the same time. Begin by making a few anchor holes and securing the Fome-cor to the Coroplast with screw posts, then make the remaining holes. Insert the larger, hollow screw posts first through the Coroplast from below, then up through the Fome-cor. Insert the smaller screw posts from the top, down into the Fome-cor and the hollow part of the fastener. Tighten the screw posts until the slotted heads are recessed enough to allow the second layer of Fome-cor to lie flat.
  10. Adhere the upper Fome-cor mat to the lower one using PVA.
  11. Apply a paper strip to the inside edge of the Fome-cor sink mat. This strip protects the map from the abrasive edge of the cut foam. Cut several long strips of acid-free cover weight paper, enough to go around the window of the mat. The width of the strips is equal to a little less than the depth of the completed mat (measured at the inside). The grain should be long.Apply thick PVA or PVA-paste mix to one strip and begin adhering this first strip at one corner of the sink mat window as shown in figure 13. After the strip is in place, work it for several minutes with your hands and/or a bone folder. A Teflon folder works particularly well here.Repeat for each strip until the entire inside edge of the sink is covered. The ends of the strips can be butted to each other or slightly overlapped.
  12. Cover any joins in the top mat with strips of acid-free paper.
  13. Adhere labels. We adhered a photograph of the map's verso to the underside of the cover.
  14. Allow adhesive to cure for a week with the housing open.


The author would like to acknowledge the helpful insight and opinions of her colleagues at the Humanities Research Center as well as the contribution of Elizabeth Dube to the preliminary stages of this paper. The figures illustrating the Kraus instructions were created by Liz Dube.

Copyright 1997 American Institute for Conservation of Historic and Artistic Works