Isolation tank

An isolation tank, sensory deprivation tank, float tank, float pod, float cabin, flotation tank, or sensory attenuation tank is a water filled, pitch-black, light-proof, soundproof environment heated to the same temperature as the skin.

Method

The tank is filled with 25 centimeters (10 in) of water which contains enough dissolved Epsom salt to create a specific gravity of approximately 1.25–1.26, enabling a person to float freely with their face above the water. In order to reduce thermal sensations, the water in the float tank is maintained at approximately skin temperature, around 35 °C. One typically floats without clothing to minimize tactile sensations, and earplugs are worn during floating both to minimize auditory sensations and to keep Epsom salt out of the ear canal.

Several different tank designs exist. Pod and cabin designs utilize enclosures with doors to enter or exit the tank, whereas pool designs are built from circular fiberglass and lack an enclosure to reduce the risk of claustrophobia. The pool design is housed in a room that is soundproof and lightproof, with tightly controlled ambient air temperature and humidity.

History

The isolation tank was developed in 1954 by John C. Lilly, a medical practitioner and neuropsychiatrist. During his training in psychoanalysis at the US National Institute of Mental Health (NIMH), Lilly experimented with sensory deprivation.

Widespread commercial interest and use of the isolation tank did not occur until 1972, when Glenn Perry, a computer systems programmer, began selling the first commercial tanks after he attended a five-day workshop by Lilly.

In 1981, there were about $4 million in sales and rentals in the industry, and expectations were that the market would grow, spurred by the film Altered States (a film starring William Hurt as a psychopathologist experimenting with a flotation tank), which came out in 1980.