Leftovers: The presence of manufacture‐derived aquatic lipids in Alaskan pottery

Abstract

Lipids preserved within the walls of ancient pottery vessels are routinely analysed to reveal their original contents. The provenience of aquatic lipids in pottery is generally connected to vessel function (e.g., for cooking or storing fish, shellfish and aquatic mammals). However, ethnographic reports from early historic Alaska mention the use of aquatic oils for waterproofing low‐fired pottery. Results of lipid residue studies on Alaskan pottery reflect an exclusive function of pottery to process aquatic resources. However, can one be sure these residues are the product of vessel function and not a remnant of the manufacturing process? The study presents the results of an experiment where the preservation of aquatic lipids during the firing process at different temperatures was measured. It was found that nearly all lipids were removed at firing temperatures of ≥ 400°C. Petrographic analysis of Alaskan pottery samples indicates that firing temperatures were generally > 550°C but < 800°C. The contribution of pre‐firing manufacture‐derived lipids to samples fired at these temperatures may be regarded as negligible. While the possible presence of aquatic lipids from post‐firing surface treatments cannot be excluded, such treatments appear unnecessary for well‐fired pottery.

A pottery biography: considering the entire lifecycle of a pot in organic residue analysis

“…However, several studies mention that, depending on the parameters involved in the firing process, part of the organic matter could be preserved (Gabasio et al, 1986;Johnson et al, 1988;Rice, 1987). Recently, several experiments have been set up to test this hypothesis (Admiraal et al, 2020;Reber et al, 2018). Clay sherds naturally rich in organic matter or enriched have been fired at different temperatures, in muffle furnaces or in fireplaces.…”

“…Now that organic residue analysis is well established as an archaeological science, we observe a new interest in these issues, and recent studies are beginning to explore again the parameters that impact the organic signal, beyond the use of the pots (e.g. Admiraal et al, 2020;Drieu et al, 2019;Goldenberg et al, 2014;Reber et al, 2018). For once, the present paper will focus on all the stages of the ceramic lifecycle, trying to highlight as many parameters that influence the absorption and preservation of organic matter at all stages of the life cycle of the vessels.…”