A double boiler is a tool used in cooking and crafts to avoid exposing the substance being heated to
direct heat and to provide a slow even heat to the substance being heated. This typical consists of two
saucepans that can be
nested within each other (such as a 4
quart and a 2
quart). The larger, outer saucepan is filled with water while the smaller, inner saucepan is filled with the substance being heated. This is typically either a
sugar with cooking, or wax with
crafts.
One important feature of the double boiler is that it is impossible to heat the mixture above the boiling point of water (sea level: 100C or 212F).
Double boilers can also be purchased that fit exactly together rather than having to use the two saucepan method described here.