 The practice of covering the body or face with plaster was also short-lived, as improved mummification techniques offered a better chance of preserving the body than covering it with plaster.Plaster masks that were formed directly around the head of the deceased are now thought to represent an early stage in a process that would lead to the full mummification of non-royal bodies.eventually evolving into the practice of creating masks made of cartonnage, consisting of linen layers mixed with gesso.