In ancient Egyptian mummification, the body was traditionally treated with natron for forty days.
Natron was a naturally occurring salt mixture used to dry the corpse. Removing moisture was essential because damp tissue decomposes quickly. Embalmers placed the body in or covered it with natron, allowing the salt to draw out water from the skin and internal tissues.
The forty-day drying period is often confused with the full seventy-day period traditionally associated with mummification. The seventy days describe the complete embalming process in the familiar classical account, including drying, treatment, wrapping, and preparation for burial. Forty days refers specifically to the desiccation stage.
Ancient techniques varied according to period, social status, and available resources. Some burials were simpler than elite royal or high-status mummifications. Nevertheless, natron remained one of the defining materials of Egyptian embalming and is central to understanding how bodies could be preserved for the afterlife.