Adipocere is a chemical change in the body fat, which is hydrolyzed to a waxy compound – not unlike soap. This process is most commonly seen in bodies found in wet conditions (i.e. submerged in water or buried in wet ground) but this is not always the case and some bodies from dry vaults have been found to have adipocere formation.

In the early stages of formation, adipocere is a pale, rancid, greasy semi-fluid material with a most unpleasant smell. As the hydrolysis progresses, the material becomes more brittle and whiter and, when fully formed, adipocere is a grey, firm, waxy compound that maintains the shape of the body. The speed with which adipocere can develop is variable; it would usually be expected to take weeks or months, but is reported to have occurred in as little as 3 weeks. All three stages of adipocere formation can coexist and they can also be found with areas of mummification and putrefaction if the conditions are correct.