Float tank (aka flotation tank, sensory deprivation tank, or isolation tank):
A tank filled with water that has enough Epsom salt mixed in to allow a person to float on the surface. The water is kept at skin-temperature, making it imperceptible, and the tank is sound-proof and pitch-black, creating a place for our bodies to be free from gravity and all stimulation from the outside world.
An Abstract Abstract
A float tank is not as much an object as it is an environment. An environment whose purpose is to act as a counterbalance to every other interaction we have with the world around us. It is the pursuit of a pure nothingness. A place of rest. It is an environment that allows our bodies and our minds to sink away from the society that has been built around us, and to instead turn focus internally. A chance to check in with ourselves, uninhibited and unadulterated by the external forces that are otherwise omnipresent. There is no magic in the float tank, the magic is us. Our bodies have spent millions of years learning how to take care of themselves, and the float tank simply provides the optimum environment with which to do it.
The float tank as we know it today comes in a variety of shapes and sizes. They are called by several different names: most commonly ‘rooms,’ ‘tanks,’ and ‘pods.’
Each tank holds a solution that is about 2/3 water and 1/3 Epsom salt. With the 10” of solution that most float tanks are designed to hold, this comes out to about 850 lbs of Epsom salt. The Epsom salt adds density to the water, which in turn makes our bodies very buoyant. As a person lies on their back in the float tank, their body floats on the surface, half in and half out of the water. This buoyancy has an incredibly rejuvenating effect on the human body.
How salty is the float tank?
Buoyancy in the float tank is most commonly recorded as a measurement of specific gravity (a comparison of relative densities). With pure water holding a specific gravity of exactly 1, the ocean comes in at about 1.025. Float tanks usually sit in the 1.27 – 1.3 range, making them up to 12 times more buoyant than ocean water.
Ocean water is about 3% salt.
Float tank water is about 35% salt.
The closest experience to this that most people know of is the Dead Sea, a hypersaline lake in Israel known for its ability to keep people afloat. The specific gravity of the Dead Sea is about 1.16, just half that of a float tank.
At a specific gravity of about 1.32, the salt has reached its saturation point (at the temperatures that float tanks are kept). This means that any more salt will refuse to even dissolve into the solution, gathering in clumps at the bottom, or floating in crystalline form on the surface. Basically, they have so much salt in them that float tanks skirt the border between a liquid and solid state of matter.
The temperature of the water is kept at 93.5 degrees Fahrenheit, the average external temperature of the human body. This is a temperature known as skin-receptor neutral, meaning the water creates no cues for the skin to report as tactile stimulation.
The tanks and the rooms around them are soundproofed to block all noise from the outside world, and light-trapped to create complete and total darkness.
The combination of these elements creates an environment that is free from all external stimulation. Our body responds to this environment by basically taking a gigantic mental and physical sigh of relief. No longer worried about filtering the outside world to look for potential danger, our production of stress-related hormones drop to almost nothing, our brainwaves lower in frequency to a state associated with mental relaxation and free-thinking, and there is a natural spike in the neurochemicals that make us feel joy.
All of this is compounded by the inherent relaxation created by absorbing Epsom salt (Magnesium Sulfate). While used primarily in the float tank to actually make people float, Epsom salt comes with the added benefit of softening skin and hair, cleansing and detoxifying the body, and getting people the magnesium most of us are lacking.