Preparation of Sub-Fossil Ivory: Case Study of Mammut americanum
Authors:Michele Maybee, Robert Salazar
Mentor:Robert Gray, Professor of Paleontology, Santa Barbara City College
Ivory’s high organic content and hygroscopic nature renders it especially vulnerable to fragmentation in arid environments. In particular, subfossil ivory from Mammuthus columbi, Mammuthus exilis, and Mammut americanum from the marine terraces of Santa Barbara County and the Channel Islands are often fragmented beyond current preparatory efforts. Through the development of novel preparatory techniques, we strive to restore structural integrity to subfossil ivory tusks, so they may become available for researchers, artists, and exhibition. Subfossil ivory is different from permineralized bone in how it is worked and the unique physical properties it exhibits. Properties unique to subfossil ivory include its light-sensitive coloration, luster, relative softness, and sensitivity to temperature and humidity. While durable and homogenous in life, tusks fracture in three distinct patterns following desiccation in an arid environment. The most prominent of these fracture regimes leaves the tusk parted into a series of concentric laminae. Irregular transverse fractures and radial fractures intersect these concentric laminae and collectively eliminate the structural integrity of the tusk by reducing it to a myriad of tabular units. The restoration of a highly fragmented subfossil tusk from M. americanum initiated our development of preparatory techniques. Restoring the outermost concentric lamina by rejoining and replacing the most surficial tabular units with an Auqazol-200 based filler allows the interior to be consolidated in place. Final consolidation with Butvar B-72 dissolved in acetone leaves the tusk rigid enough to be handled and bear its own weight. Sanding and polishing then finishes the preparation process. The utilization of subfossil ivory preparatory techniques allows these ancient specimens to become a resource of scientific and natural aesthetic value for researchers and exhibition. Our future work includes the development of techniques for restoring the tusk’s original morphology from deformation incurred during excavation and the adaptation of subfossil ivory conservation techniques.