What is a double boiler and why do I need to use one?
A double boiler is a pot within a pot. The outer pot contains water which safely transfers heat to the inner pot without allowing hotspots that could exceed the burning point of the wax and start a fire.
Never melt wax in a single pot directly over a heat source! You can easily make a double boiler from a pot and a large tin can – one- or three-pound coffee cans and "family-size" soup cans work well depending on how much wax you need to melt or, as in the case of potting guitar pickups, how large an object you need to immerse in the melted wax.