Isolation tank

An isolation tank is a lightproof, soundproof enclosure filled with about 25 centimetres of water heated to skin temperature and dissolved with Epsom salt, built to restrict a person's sensory input. The neuropsychiatrist John C. Lilly developed the isolation tank in 1954 while training in psychoanalysis at the National Institute of Mental Health, though commercial interest did not take off until 1972, when the programmer Glenn Perry began selling tanks after attending one of Lilly's workshops. The Epsom salt gives the water a specific gravity of about 1.25 to 1.26, letting a person float with only their face above the surface, and users typically wear earplugs and remove their clothing to further reduce sensory input, in tank designs that range from enclosed pods or cabins to open fibreglass pools inside a soundproof, lightproof room. Scientific literature generally refers to the experience as flotation REST, short for restricted environmental stimulation therapy, reflecting the view that the tank heightens awareness of internal bodily sensations rather than simply depriving the senses.