Wood vs. Stone Mortar Technologies: An Experimental Approach to Food Grinding Efficiency

Christina M. Murray

Abstract

Groundstone technologies have been used for millennia to process various materials, the most important being plant foods. Native Californians relied heavily on the consumption of gathered acorns and grass seeds which comprised a large percentage of their diets. Groundstone technologies such as mortars and pestles were used extensively to render these foods edible. In the Central Valley, however, large stones were not readily available for mortar production due to the presence of extensive silt and clay alluvium. Instead, hardwood mortars were often used to process foods, as documented in the ethnographic record. The effectiveness of wood versus stone for grinding foods is not well known. This paper details an experiment that gauges the relative efficiencies of two mortar designs, deep and shallow, and two raw material types, stone and wood, at grinding two foods, acorns (Quercus lobata, Quercus douglasii) and chia seeds (Salvia hispanica). Efficiency is assessed by comparing how much time it takes to manufacture each item against the time it takes to process a specific amount of food material to a pre-defined consistency. The data are then applied to the Point Estimate Model (Bettinger et al., 2006) to predict when one design is advantageous over another.

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