STORIES 36
Experimental heating of quartzite collected from Klasies River
Silje Evjenth Bentsen taking samples of experimental fires in 2015
Example of a heated ostrich eggshell fragment
EXPERIMENTAL ARCHAEOLOGY Ostrich eggshell fragments give off a disgusting metallic stench when heated. Hot rocks produce crackling sounds while cooling down. The sand under a fire can stay above 100 °C even 10-12 hours after the fire went out. How do I know these things? I discovered them first-hand through experimental archaeology. Experimental archaeology is a term which describes practical experiments used to test an archaeological theory or understand an object. Quite often researchers need to perform a lot of experiments, redesigning the research at each stage, to achieve the desired result. One example of this process is a study of enigmatic fractured and reddened rocks from Klasies River, published by SapienCE post-doc Silje Evjenth Bentsen and Professor Sarah Wurz in 2019. The experimental work started in 2015 during a University of the Witwatersrand excavation at Klasies River, a Middle Stone Age site in the Eastern Cape Province, South Africa. The excavation team knew that Klasies contained numerous
small patches of ash from ancient fires, and we wanted to understand how warm these fires were and how long they burned for. This information could help us understand what the fires could be used for and how people used the site. Using locally collected wood, we created a number of small experimental fires, and discovered that while they produced enough heat to cook food they could only be used for a few hours. However, neither the temperature nor duration of these fires was sufficient to explain reddened and fractured quartzite rocks that we had recently excavated in Klasies River. “Why are red and fractured quartzite rocks important?” you might ask. We know that some rocks become reddened and fracture when exposed to heat from a fire, so the quartzite excavated from Klasies River might provide us with clues about how fire was used at the site. However, in 2015 we did not know how the quartzite rock found around Klasies River reacted to heat, and even if it did redden and fracture,
