Vacuum pan salt is produced in large enclosed tanks known as vacuum pans or vacuum salt crystallizers. The tanks are filled with brine, which is heated by injecting steam into the tank. The steam heats the brine and causes it to boil. As the brine boils it produces additional steam, which is fed into a second vacuum pan and causes its water to boil. Three or more vacuum pans are connected in a series to make efficient use of the steam. As the brine in the tanks becomes saturated with salt, crystals of salt begin to form in the tanks.

Salt produced in a vacuum pan has a much higher purity than salt produced from an underground mine. Why? Vacuum pan salt is usually made from brine produced by solution mining. When the salt was dissolved underground, solid particle impurities in the salt were not dissolved and remained underground.

Vacuum pan salt also has a different texture – its crystals are very small. Some vacuum pan salt also has a different crystal shape – flake-shaped crystals instead of cubic-shaped crystals. Flake salt is a specialty product sold for table use. It is also preferred by many producers of baked goods, butter, cheese, and other products (Date from the United States Geological Survey, Minerals Yearbook for 2016.