In the original concept, the solitude, isolation and confinement tank was devised as a research instrument in 1954. In the ensuing twenty-three years of working with tanks, I have found various ways of making the apparatus simpler and safer.
In the original tanks, we were required to wear rather complicated head masks in order to breathe underwater. These have been eliminated completely.
In the latest models of tanks, we use a saturated solution of Epsom salts (MgSO4- 7H2O) at a solution density of 1.30 grams per cubic centimeter. It was discovered that this density of solution allows one to float supine and have the whole body at or near the surface of the liquid. One's hands float, one's arms, legs, feet and, most important, one's head, float. We have found that even the thinnest person with the least amount of fat floats in this way in the tank.
With these simplifications of the technique it has turned out that we have devised a method of attaining the deepest rest that we have ever experienced. The research instrument has become a practical possibility for use by those untrained in research.
These simpler, salt-water tanks are offered commercially.