A float tank, also known as a sensory deprivation tank, is a specialized environment designed to minimize external stimuli and create a state of deep rest. The primary function of this chamber is to remove the sensation of gravity, light, and sound, allowing the user to experience profound relaxation. This unique environment is achieved by filling the tank with a shallow layer of water saturated with a specific compound. The concentration of this compound is the most important factor in the floating experience.
The Specific Salt Used
The salt used in floatation therapy is not common table salt (sodium chloride), but rather magnesium sulfate, widely known as Epsom salt. This chemical compound is selected because it is non-toxic and non-irritating to the skin and eyes, even in extremely high concentrations. Unlike sodium chloride, the float solution does not cause stinging in small cuts or abrasions. Furthermore, the magnesium component is thought to be absorbed through the skin, potentially helping the body regulate magnesium levels and contributing to muscle relaxation.
Quantitative Salt Concentration
The amount of salt dissolved in a float tank is immense, creating a super-saturated solution. While tank sizes vary, a typical float pod containing 180 to 200 gallons of water will hold between 800 and 1,200 pounds of magnesium sulfate. This vast quantity of salt is dissolved in a shallow solution, usually kept at a depth of only 10 to 12 inches. Float tank solutions often achieve a salt saturation level of 30% to 40% by weight, which is significantly denser than the natural concentration found in the Dead Sea.
How Salt Creates Buoyancy
The physical principle that allows a human body to float effortlessly is the dramatically increased density of the water, measured as specific gravity. Specific gravity is a ratio that compares the density of a substance to the density of pure water (1.0). The human body has a specific gravity ranging from 1.02 to 1.09, meaning a person naturally sinks or floats slightly in tap water.
When massive amounts of magnesium sulfate are dissolved, the specific gravity of the solution is raised to a range of 1.25 to 1.28. Because the density of the solution is much greater than the density of the human body, the buoyant force exerted by the liquid is powerful enough to support the entire body mass. This high density allows the body to float on the surface with most of its mass above the water line, creating a sensation of weightlessness.