Hot rock boiling with granite, sandstone, and siltstone from Sawyer County, Wisconsin

Abstract

Indigenous people used heated rock to cook food in earth ovens by dropping hot rocks into containers and by using hot rock as a griddle. These cooking methods were likely widespread in prehistoric societies throughout the world including North America and still take place today. Past and present ethnographic sources from northern Wisconsin refer to hot rock boiling for cooking and heating drinking water or tea. Granite, sandstone, and siltstone rocks were gathered from Sawyer County, Wisconsin for use in a hot rock boiling experiment. The rocks were heated in an elm wood fire and used in three rock boiling sessions. The heating sessions were evaluated to determine that thermally altered rock has distinct regional characteristics, how to reduce work and increase cooking potential, and to identify the factors that contribute to thermally altered rock weight loss.