Isolation tank

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An isolation tank is a lightless, soundproof tank inside which subjects float in salt water at skin temperature. They were first used by John C. Lilly[1] in 1954 to test the effects of sensory deprivation. Such tanks are now also used for meditation and relaxation and in alternative medicine. The isolation tank was originally called the sensory deprivation tank. Other names for the isolation tank include flotation tank, John C. Lilly tank, REST tank, sensory attenuation tank, and think tank.

A Flotation Tank



Peter Suedfeld and Roderick Borrie of the University of British Columbia began experimenting on the therapeutic benefits of flotation tank usage in the late 1970s. They named their technique "Restricted Environmental Stimulation Therapy" (REST).

Tank design and usage[edit]

The original float tanks involved being entirely submerged in the tank, and people were required to wear complicated head-masks to breathe, and uncomfortable tight clothing that constricted the blood flow in certain areas. Many users claimed that the mask and clothing detracted from the isolation experience by creating uncomfortable physical conditions, and that being entirely submerged in water led to the fear of drowning. The tight fit of the mask seal around the face and the retention strips wrapping around the back of the head were uncomfortable in long sessions. The constant hissing of the air valves and bubbling of exhaust air out of the mask prevented the possibility of silence. The faceplate of the mask was typically solid black for visual isolation, but then the tank user needed help entering and leaving the isolation tank since the mask blinded them. The tight neoprene clothing was extremely uncomfortable in sensitive areas such as the genitalia, and constricted blood flow and mobility in other areas.[5]

In current tanks, a solution of epsom salt is used for an increased density. The subject can now float with the face above the water, although the ears are still submerged when the subject is in a relaxed position. Hearing is therefore greatly reduced, particularly when using ear-plugs as protection against the salt water. When the arms float to the side, skin sensation is greatly reduced because the air and water are the same temperature as the skin, and the feeling of a body boundary fades. The sense of smell is also greatly reduced, especially if the water has not been treated with chlorine.

The growing number of commercial float tanks has brought increased regulation of disinfection. In the US different states have implemented different rules. In Europe, the DIN 19643 bathing water standard requires automated chlorination controlled by REDOX (ORP) measurement. Chlorine, bromine and peroxide disinfection have all been used successfully. There is doubt about ozone safety because of the closed air space. For this reason, H2O2 is cited by many industry professionals as a safer and more desirable sanitation agent.[6]

Generally, users of isolation tanks enter the pool nude. The elastic material of a tight-fitting swimsuit can create uncomfortable compressed stress points on the skin during the session. Due to the high salt content, the water is rarely changed, and all users are expected to shower, wash with soap, and rinse clean prior to entering the tank to avoid getting oils from their skin into the tank. Bathing is again needed after a session to remove excess epsom salt from the skin, and white vinegar is often used to remove excess salt from the ear canal and hair.

Most isolation tanks use a surface skimmer, cartridge filtration, and disinfection means, including ultraviolet sterilization and chemicals to keep the water free of microbes and sediment. These machines are usually turned off during a session to keep the isolation space as quiet as possible. A ring heating system can be used around the outer walls of the tank so that warm water rises around the edges of the pool, travels towards the center, and then sinks under the tank user. This very slow water convection flow helps to keep the user centered in the middle of the pool. The small waves caused by breathing also aid in centering the subject.

Cut through a float tank.

Isolation tank construction and plumbing is typically all plastic. Typically glass reinforced resins are used. High quality flotation tanks may use acrylic or medical stainless steel which is impervious to the strong salt solution and more importantly the disinfectants. Epsom salt is not corrosive in the way sodium chloride is, but unsealed stone and concrete surfaces outside the tank can be damaged by splashed or dripped salt water as the recrystallizing salt opens up cracks and fissures as it dries. Chlorine used as a disinfectant can attack some surfaces such as marble.

It is useful to have a shower stall in the same room as the tank. Before a session, the tank user can transfer directly from the shower to the tank without drying off, which helps prevent oil from the user's skin from entering the water. Following the session, they can immediately rinse off which minimizes the dripping of corrosive salt through the building.

Having plumbing facilities immediately next to the tank is also helpful when the water must eventually be changed to prevent microbe growth. The plumbing, including the drain pipes, should be constructed of plastic to prevent deterioration from the salt. The salt concentration may need to be diluted when discarded, to prevent damage to small private wastewater plumbing systems.

Types of sessions[edit]


Spas sometimes provide commercial float tanks for use in relaxation. Flotation therapy has been academically studied in the USA and in Sweden with published results showing reduction of both pain and stress.[8] The relaxed state also involves lowered blood pressure and maximum blood flow.


Flotation therapy[edit]

Flotation therapy is therapy that is undertaken by floating in a warm salt water in a float tank.[9]





Research in Sweden has demonstrated the therapeutic effect on stress and pain.[12]


The natural tendency of the body in the floating posture at the correct temperature is to dilate the blood vessels, reducing the blood pressure and maximizing blood flow. The brain activity normally associated with postural muscles is reduced to a minimum. In this state, which we can call the floating state, natural endorphins are released reducing pain[citation needed]. Lactic acid removal is accelerated. Flow in the lymphatic system is increased.


The effect on stress[edit]



The effect of the salt[edit]


It has recently been discovered that there is a secondary effect which is important to flotation therapy. Magnesium is absorbed through the skin due to natural molecular diffusion. This tends to correct magnesium deficiency.[14] Magnesium is absorbed from the diet but in many areas of the world, over-cropping without adequate replacement of magnesium makes the normal diet low in magnesium.




Latest research[edit]

New research undertaken at the Human Performance Laboratory at Karlstad University Sven-Åke Bood[15] concludes that regular flotation tank sessions can provide significant relief for chronic stress-related ailments. Studies involving 140 people with long-term conditions such as anxiety, stress, depression and fibromyalgia found that more than three quarters experienced noticeable improvements.

Dr. Bood commented: "Through relaxing in floating tanks, people with long-term fibromyalgia, for instance, or depression and anxiety felt substantially better after only 12 treatments". Research targeted the effectiveness of floatation treatment with regard to stress related pain and anxiety over the period of seven weeks. 23 percent of the participants became entirely free of pain and 56 percent experienced clear improvement.

Broken down to various symptoms, the results were as follows: 23 percent slept better, 31 percent experienced reduced stress, 27 percent felt less agony and 24 percent became less depressed or got rid of their depression altogether. The research also confirms the findings of an earlier thesis that flotation, after only twelve sessions, substantially improves sleep patterns leaving users more optimistic and with reduced nervousness, tension and pain. Relaxing in a weightless state in the silent warmth of a flotation tank activates the body's own system for recuperation and healing, said Sven-Åke Bood. What researchers find particularly gratifying is that the positive effects were still in evidence 4 months after the floating treatment ended.

Notable users[edit]

The physicist Richard Feynman's experiences in a sensory deprivation tank were documented in the popular book Surely You're Joking, Mr. Feynman!. Feynman was invited to try the isolation tank at John Lilly's home after Lilly attended one of Feynman's popular lectures on quantum mechanics.

In a number of recent videos on YouTube and his own podcast, American stand-up comedian and television celebrity Joe Rogan describes his personal experiences with isolation tanks and shares his insights into using them for various purposes, such as exploring the nature of consciousness and improving health and well being.[16]

See also[edit]


  1. ^ Lilly, John C. & E.J. Gold (2000). Tanks for the Memories: Flotation Tank Talks. Gateways Books & Tapes. ISBN 0-89556-071-2
  3. ^ Gelb, Michael; Sarah Miller Caldicott (2007). Innovate Like Edison. Dutton. p. 140. ISBN 0-525-95031-1. 
  4. ^ Lilly, John Cunningham (1996). The Scientist: A Metaphysical Autobiography (3 ed.). Ronin Publishing. p. 102. ISBN 0-914171-72-0. 
  5. ^ Seudfeld, Peter. "History of Floating". Portland Float Conference. Float Conference. Retrieved 9 March 2013. 
  6. ^ Health aspects of air pollution with Particulate Matter, Ozone and Nitrogen Dioxide. WHO-Europe report 13–15 January 2003 (allegedly available somewhere as PDF)
  7. ^ Talley, Graham. "About Floating Guide". About Floating Guide. Float Tank Solutions. Retrieved 9 March 2013. 
  9. ^ Michael Hutchison, "the book of Floating", 1984,2003, ISBN 0-89556-118-2
  10. ^ Efrati, Amir. "Float Centers Gaining Steam". The Wall Street Journal. Retrieved May 15, 2013. 
  13. ^ "Restricting environmental stimulation influences levels and variability of plasma cortisol". Float Tank Association. Retrieved May 15, 2013. 
  15. ^ Sven-Åke Bood (2007). Bending and Mending the Neurosignature: Frameworks of influence by floatation-REST. Karlstad University. ISBN 978-91-7063-128-3
  16. ^ The Sensory Deprivation Tank - Joe Rogan on YouTube

Further reading[edit]

  • Lilly, John C. (1 Lilly, John C. (1990). The Center of the Cyclone. Marion Boyars Publishers Ltd. ISBN 0-7145-0961-2
  • Suedfeld, P, Turner, J.W.Jr., Fine, T.H. (Eds) (1990) Restricted Environmental Stimulation: Theoretical and Empirical Developments in Flotation REST Springer. Spinger-Verlag ISBN 0-387-97348-6
  • Sensory Deprivation Tank Sensory deprivation tank information, positive effects, best practices and techniques.