The easiest alternative to a double boiler is to place a metal mixing bowl inside a saucepan; the bowl should be large enough and wide enough so that it doesn't touch the water in the pan. The bowl's sides should also be high enough to keep your foods from splattering when you stir the ingredients in the bowl. The bowl should fit snugly within the saucepan to keep the water or steam from escaping and ruining the sauce or chocolate. Fill the saucepan with about an inch of water.
Silicone inserts are collapsible inserts designed to be used in a variety of pan sizes. They are inexpensive alternatives to double boilers. Silicone inserts are dishwasher-safe, oven-safe, microwave-safe and non-stick. To make sure the insert you choose fits your pans, measure the depth and diameter of your pans before you buy the insert. The insert will need to fit closely and have several inches of room between the insert and the pan. Silicone transfers heat more slowly than other materials.
The microwave is a good alternative to a double boiler for simple melting projects. Chocolate or butter can easily be melted in a bowl in the microwave. Chop the food into small, uniform pieces and microwave it on the lowest setting of the microwave oven. Set the timer for 30 seconds at a time until the food is melted, stirring between each cycle.
Use two saucepans of different sizes in place of a double boiler. Make sure the smaller pan does not touch the bottom of the larger pan. For non-food items like candle wax or soap, a tin can placed in a pan with shallow water works well.