A handwritten circa 1721 Navigation Notebook currently featured in our exhibition Harry Potter: A History of Magic, on view until January 27, 2019, contains all sorts of information that may be helpful in determining one’s location at sea, including descriptions of the constellations, tables, charts, and two volvelles. A volvelle is a paper chart with movable parts. (Visualize the spinner for a board game and you’ll get the idea.) Conservation treatment of the notebook included stabilization of one of its volvelles. Although the volvelle is not visible during the exhibition, stabilization was necessary to prevent its further damage during handling.
The Navigation Notebook’s first volvelle, still fully intact, is made up of two paper circles held together with knotted thread and a small metal pin. The larger, outermost circle is adhered to the page and does not move, while the smaller circle can be rotated. The inscription above the volvelle gives instructions on determining “full sea.”
The second volvelle is missing its center movable piece. The large outer circle is drawn directly onto the textblock paper. The inscription above the volvelle explains how it can be used to determine on which “letter,” or day, of the month Sunday will fall.
What makes these charts especially handsome is the use of colored inks. However, green ink is unfriendly to paper, as the copper components of the pigment break down cellulose—the building block of paper fibers. One way to stabilize areas of corroded ink without the use of dangerous chemicals is to reinforce the paper with thin but strong Japanese paper. Care must be taken to limit the introduction of excess moisture because it will accelerate copper corrosion. Since most adhesives contain water, we used pre-made solvent-set paper. This adhesive backed Japanese paper is made in advance and allowed to dry completely. The adhesive is reactivated when needed with the smallest amount of water mixed with ethanol, which evaporates quicker than water alone. This method allows the conservator to reinforce delicate areas of ink corroded paper without affecting the pigment.
Even though the volvelles are not visible in the exhibition, their fragile state necessitated conservation intervention. The damaged paper underneath the corroded ink was in danger of being lost during handling and installation.
To learn more about volvelles, visit the Grolier Club’s website.
Find the Navigation Notebook on view in Harry Potter: A History of Magic in the Astronomy gallery. (The page on view includes descriptions of the constellations Draco the Dragon and Cygnus the Swan!)
This post is by Katarzyna Bator, Assistant Conservator.