sand bath

Short definition from Wiktionary

Noun

1. 1
   A piece of laboratory equipment consisting of a container filled with heated sand, that is used to provide an even source of heat.
2. 2
   A bath in which the body is immersed in hot sand.
3. 3
   The rolling of birds in sand, by which they dust themselves over to cleanse the skin and feathers; the act of pulverizing.