April 2019
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This report presents an experiment in which four starch sampling methods are compared in order to identify the most successful and effective technique for starch extraction from large groundstone and milling features in the field. Testing archaeological specimens in situ is necessary when the artifact is too large or cumbersome to bring back to a laboratory (Pearsall 2015). In addition, preliminary testing in the field allows researchers to obtain quick results that provides guidance for ongoing excavation and sampling methods. Agitation is needed to release both post-depositional sediment and adhered starch from a specimen, which then is collected as an aqueous accumulation with a pipette. This project tested the hypothesis: if ultrasonic vibrations from electric hand instruments (electric toothbrush and sonicating facial scrubber) are more effective at dislodging starch from groundstone, then more starch grains should be observed in prepared slides when compared to those using non-electric instruments (plastic pipette and regular toothbrush). The vibrations of sonicating instruments have the power to deeply clean uneven or porous surfaces, which may be necessary when dealing with pitted ground stone. Multiple heads for modern electric toothbrushes can be purchased quite cheaply, so this seemed to be an economical tool to test for the field. The sampling methods used here included two sonicators and two manual tools. The procedures for each were similar: a water wash was used along with a tool to agitate the wetted sample (either manually or through sonication), the liquid and tool were each retained, the tools were washed, and the presumably starch filled liquid from each was then mounted on slides and viewed under a polarizing light microscope. The materials tested were pieces of sandstone (imitation metates and manos) taken from Putah Creek Wildlife Area, Solano County, California, which were washed and used to grind wheat, maize, and manioc. The first three pairs of stones were used for one taxon each, while the fourth received all three taxa processed on it in turn before sampling. These four collections were completed so that the differences in starch deposition due to plant taxa would not compromise the results.