The salt used in the high temp pot is 50% sodium chloride and 50% Calcium Chloride. Cheap to make from stuff available at the hardware store.
It is very tempting to use inexpensive materials in the construction of a high temperature salt pot ... DON'T. Once you see an incandescent liquid that has a viscosity lower than water, and almost no surface tension, it sobers you very, very quickly.
This stuff is like a venomous snake ready to strike. Give it just the least opportunity ... and you'll pay the price.
NO WATER should be introduced into a salt pot. The results will be a steam exposion that ejects molten salt at high velocity.
Note the knife on the top of the pot being preheated to drive off an adsorbed water. Molten bluing salts are commonly used for the low temperature pot. They are available from Brownell's. They are a mixture of sodium and potassium nitrate. These are the oxidizers used in black powder. DO NOT introduce organic materials into molten bluing salts ... an explosion may result!