It is part of our “Best of Float Talk” series which includes posts made on the Float Talk discussion board.
After many years of handling customers with crystallized salt in pumps and tanks, I realized there is a better way than dealing with salt crystals freezing up pumps and tanks. The following is what I have come up with:
The density of the solution needs to be appropriate to the coldest the room ever gets.
This is because the solution in the filtration system is generally at room temperature. A cold solution will not hold as much salt as a warm solution. So salt saturation is less at a colder temperature. If you keep the density at 1.25 or below, you can have the tank in an environment that drops to 50° F or 10°C without doing anything or worrying about anything. We have not noticed anyone having trouble floating well at this density. So why bother with a higher density? If the environment sometimes goes to 40°F or 4° C then put the density at 1.24.
How do you make sure it stays at that density or below?
Keep measuring the depth of the solution with a ruler, and keep it near 10″ or 25 cm. Eventually, after maybe 700 floats and adding water every 200 floats, the density, while floating, will seem too low to float well, and you will want more salt. Then add salt and use your hydrometer. But until then, I find a ruler a lot easier to use, than a hydrometer.
A bit of history on the subject…
By the way, John Lilly never floated in a solution that was above 1.035 until 1973, (that’s 19 years of research before “floating” actually started). When he gave me the specifications for how to make a tank in 1972, he suggested, if I wanted, I could add 3% sodium chloride to float better. (He had the ocean flowing through his tank in the Virgin Islands.) Up until 1973, the water was 20″ deep and we would bend our legs at the knee and do dolphin breathing. That is, fill our lungs and hold our breath, then when we needed to breathe again, we would exhale quickly, and inhale right away, before we slipped under the water. I didn’t float as well as he did. So when I set up my tank I added 10% sodium chloride instead of 3% like he told me. That worked well and floating was born. So when I set up one of my tanks for him at a workshop he was giving, I made the solution 10% salt. When he experienced that, he said, “Lets try saturation”. (Later, he suggested epsom salt, as it seemed less abrasive to the skin than sodium chloride.)
So, there is no reason we can’t try 1.24 or 1.25. If you want to have a density of 1.30 for some reason, then just keep your room temperature at 95°F or 35°C or ABOVE. In other words the saturation point for epsom salts, you need to concern yourself with, is the saturation point of the solution in the filtration system which is at room temperature NOT at tank temperature. Is this clear? I think it is important to make this clear, to save a lot of people a lot of grief.