Discipline: Chemistry and Chemical Sciences
Subcategory: Materials Science
Krytal Cunningham - University of California, Los Angeles
Co-Author(s): Ioanna Kakoulli
Archaeological materials and ancient technology not only inform raw material selection and production operation sequences, but also can inspire the chemistry and manufacture of modern materials with improved properties. One such example the cobalt (Co) aluminum (Al)-spinel pigment, developed in and used in Egypt over 3500 ago, during the New Kingdom (16th to the 11th century BC). This cobalt-based spinel structure produced from natural raw materials and processed at high temperatures, was of great value and was characterized by highly specialized craftsmanship. A spinel has a AB2O4 (i.e. CoAl2O4) structure, consisting of two metallic cations A2+ and B3+ in tetrahedral and octahedral positions. They have exceptional mechanical properties and ability to perform at high temperature environments. Cobalt blue ceramic pigments were produced and used for a very short period of time, mostly during the 18th Dynasty, then suddenly disappeared around the 20th Dynasty (~1100BC). In contrast to the cobalt-containing glasses from Egypt, there are very few scientific studies on the cobalt-based blue pigment and there are still unanswered questions regarding the pigment’s chemistry and production method, as well as, the nature and location of the raw materials used: are these pure CoAl-spinel and how where they produced? Did the raw materials include cobalt-rich alums from Egypt? To answer these questions, in this research we apply a multiscale and multianalytical approach based on electron microscopy and X-ray spectroscopies to investigate the relationship between composition, structure and properties and how these relate to the production method and the operational sequences (chaîne opératoire) for the transformation of the raw materials into a cultural product and to infer raw materials choices and availability. Preliminary results indicated significant amounts of zinc (Zn) and nickel (Ni), in the cobalt blue pigment from Egypt not previously reported. Also, there is puzzling evidence whether the pigment was produced using precipitation from an aqueous solution of the cobalt alums through the addition of an alkali or through solid state reactions. References: Shortland, A., C. Hope, and M. Tite, Cobalt blue painted pottery from 18th Dynasty Egypt. Geological Society, London, Special Publications, 2006. 257(1): p. 91-99. Cavalcante, P., et al., Colour performance of ceramic nano-pigments. Dyes and pigments, 2009. 80(2): p. 226-232.
Funder Acknowledgement(s): I thank Susi Pancaldo (conservator) and Alice Stevenson (Curator) from the Petrie Museum University College London (UCL), the Scientific and Egyptian Department of the Metropolitan Museum of Art (MET) for providing the sample and objects. Dr. Bruce Dunn and his students: Chris Choi and Nick Ware, Chao Li, Rosario Esposito, Dr. Jaime Marian and his students: Nicholas Julian and Chen-Hsi Huang, Dr. Ioanna Kakoulli, the Archaeomaterials and Molecular and Nano Archaeology Lab Group for providing logistic and research support. Funding was provided by the Bridges to Doctorate by National Science Foundation Fellowship and the Eugene Cota Robles Foundation, the National Science Foundation Bridges to Doctorate Fellowship, the 20 Pearls Heritage Foundation fellowship by the Alpha Kappa Alpha Sorority, Inc. and the Andrew W. Mellon Fellowship from the Metropolitan Museum of Art
Faculty Advisor: Ioanna Kakoulli, firstname.lastname@example.org
Role: I completed the research under the guidance of my Professor (listed as a co- author)