Soap on a bone, by strangeremains

From 1786-1787 the graves in Paris’ Cemetery of Innocents (Cimetière des Saints-Innocents) were dug up to move the bones to the abandoned mines beneath the City of Lights, what would become the famous Paris Catacombs.  Fourcroy and Thouret, French scientists who supervised the exhumation and studied the decomposing bodies, found a waxy gray substance covering some of the children’s remains.  They called it adipocere, from the Latin adeps (fat) and cere (wax).

Adipocere, also known as corpse wax or the fat of graveyards, is a product of decomposition that turns body fat into a soap-like substance.  Corpse wax forms through a process called saponification and tends to develop when body fat is exposed to anaerobic bacteria in a warm, damp, alkaline environment, either in soil or water.  Grave wax has a soft, greasy gray appearance when it starts to form, and as it ages the wax hardens and turns brittle.  Saponification will stop the decay process in its tracks by encasing the body in this waxy material, turning it into a “soap mummy.”

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