A02_02

Efforts to remove ancient carbon from charred food crust: Successes and Failures

Varney R¹, Scott Cummings L¹

¹PaleoResearch Institute, Inc., Golden, United States

After radiocarbon dating reference foods, and long after some archaeologists had abandoned getting reliable dates from pottery, we conducted experimental pretreatments to remove ancient carbon from the archaeological contexts. We used a mixture of chemicals to mobilize both water-soluble and nonwater-soluble compounds in the food crusts - with many good results. We used a variety of chemical extraction methods including hydrolysis. We examined placement of the samples on the vessel - with good results. Rims generally yielded dates more congruent with dates on annuals from the same context. The key lay in viewing the cooking process as a proxy for chromatography. Carbohydrates, which are presumed to take in atmospheric carbon, burned or charred first and usually at or near the rim. Proteins charred to a lesser degree, and fats/lipids remained uncharred. Therefore, we sought to remove all of the fats/lipids and any uncharred proteins using these chemicals to be able to obtain more congruent dates, which we did. But some dates remained too old, suggesting the charred food crust had integrated proteins that contained ancient carbon. At this time we focused on a simplistic animals vs. plants model. We read about medical research that could ”uncook” proteins, returning them to a mobile rather than a fixed state. We participated in an experimental trial to test whether our charred food crust was a good candidate for this treatment. It was not. We present the multiple radiocarbon dates on these fractions for comparison and discussion.