Housing required: chiton shells seek preservation
Carried out to museum standards, rehousing is more involved than just finding a nice box. I can attest to this, having just conserved a lovely collection of marine molluscs commonly known as chitons.
The chitons, all 336 of them, were mounted on 18 pieces of cardboard. Presented to me in an unnecessarily large box, the mounted specimens were stacked one on top of another. Not a good look - and certainly not considered proper storage if long-term preservation is the goal.
Before I thought too much about designing a more appropriate housing system, I needed to evaluate the condition of the objects and perform any required conservation treatments.
Overall the chitons and boards were in fairly good, stable condition (though noted some missing and one crushed mollusc, and evidence of insect ‘nibbles’), but there were two issues that did require attention. The chitons and boards were covered in a layer of dirt and dust.
Because sharp particulate matter has the potential to abrade an object’s surface and dust absorbs moisture and pollutants (not to mention being aesthetically displeasing), I brushed the surfaces with a very soft brush while holding a vacuum fitted with a small nozzle a few centimeters away.
Then I considered three shells that were dislodged from one particular board. As I was able to determine their original, exact location and orientation, re-adhering became a good option. Paraloid B-72, an ethyl methacrylate copolymer, was employed, not only because of it’s sticking characteristics, but because the adhesion could be reversed – reversibility being an important consideration when contemplating conservation.
As for the rehousing component of this project, the primary consideration was for object preservation, but the overall space required, and availability/cost of archival materials was also taken into account. (There’s the time factor, too, but I won’t dwell on that … I spent longer on this than I probably should have!)
I knew each mounted board would fare best if stored flat (think of the effects of gravity), with no contact with other boards and shells. I didn’t want the objects to be able to move around. I wanted the overall housing to be as compact as possible – no point taking up precious space on storage shelves. I wanted to use materials on hand, and kept in mind how quantity and quality would affect the cost.
I fabricated a series of stackable trays that would fit securely within a made-to-measure box. The base of each tray is a sheet of single-wall, blue-grey corrugated board, which was built up with pieces of double-wall board to create recessed compartments for each individual object.
Every compartment was lined with a thin sheet of Cell-Aire polyethylene foam to add cushioning and slip-resistance. To make the trays stackable, Ethafoam polyethylene chocks were cut just thicker than the height of the highest chiton and glued around the tray’s perimeter. This allows the trays to be as compact as possible, while at the same time protecting the shells from potentially damaging contact.
More than just creating a nice looking box, I’m happy to report, this conserved and rehoused collection of chitons can now look forward to a better future.