This was an interesting find yesterday. It is a Ceramic Planter Heater that uses a candle to heat the core which is a steel bolt, washers, and nuts, which heats three layers of ceramic planter. The ceramic is dense and hard, holds, and distributes the heat evenly. Check it out. While there are no instructions on how to build it, the illustrations show it is not brain surgery. I may make one and try it out. In fact I may make one large enough to handle a sterno heater and see how warm it gets. If it works, maybe I’ll make a few to keep in the closet or to take one camping with me for those cold nights.