Adipocere

Also known as "grave wax," adipocere — from the Latin, adipo for fat and cera for wax) — is a grayish-white postmortem substance caused by fat decomposition, which results from hydrolysis and hydrogenation of the fatty cells that compose subcutaneous fat tissues.

Although decomposition of fatty tissues starts almost immediately after death, adipocere formation time can vary from two weeks to one or two months, on average. Factors such as temperature, embalming, burial conditions, and materials surrounding the corpse can hasten or prolong these average timelines.