When more salt is dissolved into a quantity of water than it can naturally hold, the solution is said to be supersaturated. The technique for accomplishing this is not especially difficult. It is based on the principle that hot water can hold more salt than cold water. Often supersaturated solutions of salt and other compounds are used to produce unusual crystal formations in a classroom or laboratory.
Pour 8 oz. of water into a pan, and slowly add salt. When excess salt starts to rest at the bottom of the pan, move the pan to a burner to warm it. Stir the solution until the rest of the salt dissolves into the liquid. Slowly add more salt until a few crystals remain on the bottom of the pan.
Remove the pan from the burner. Gently pour the saltwater into a clean container. Be careful to leave any undissolved salt in the bottom of the pan with a small amount of water.
Set the container of saltwater on a stable surface to cool. Even after the liquid cools, the entire amount of salt will remain dissolved in the solution. This is a supersaturated salt solution.
Add a few crystals of salt to the cooled solution. This will cause the excess salt to begin forming crystals. Salt crystals should start to form rapidly and settle to the bottom of the container. Formation of crystals proves that the solution is supersaturated.
The water does not have to boil to be hot enough to make the supersaturated salt solution.