Inspired by a guy on the internet who made a candle furnace out of tea light candles, a bread loaf pan, and some clay pots. I prefer larger, reusable candles and candle containers, even better with my candle oil lamps. I also like to use what I already have on hand or what I can acquire at the lowest price, possible.
The first picture, top left, uses a metal casing that had a battery-operated candle in the bottom. I got it at the dollar store, relieved it of the plastic candle, and set it over a candle or oil lamp. If I need extra height, I stack two smaller candles, making sure they're stable, of course! The ceramic flower pot (also from the dollar store) has a matching base, permanently attached.
The other lamp in that picture is a treasure found at a local thrift store. It only holds a tealight or votive, but the angled metal top is great for directing the heat towards whatever will sit safely on top, which honestly isn't much. This one is best kept for light and a wee bit of heat.
The centre picture is a ceramic garlic keeper, without the lid, turned upside down on a clay pot. On top is a nearly finished candle, melting for reuse. The ceramic lid from the garlic keeper comes in handy for other furnaces, too!
The picture on the right shows a larger clay plant pot base, filled with some decorative stones and a jar candle that has completely melted down. How to get that hot jar from the furnace? I use oven mitts if I must, but find it's much better to blow out the candle or lamp below and allow the wax to cool. It's ready to hold a wick once the top has solidified over. Have a pre-dipped wick, ready to press through. While the wax is molten, like pictured, is a great time to pre-dip a bunch of wicks! I love using plastic bakery clam shells for allowing my wicks to cool and then storing them in! With this furnace, I can remelt old candles or even make myself a hot cup of tea or cocoa! :D I've even reheated a mug of chili!!!
Of course, once you start playing with fire, please do so responsibly. Keep away from children, pets, flammables. Always keep on a non-flammable surface, and never leave unattended. When building your furnace, use non-flammable materials such as metal, glass, ceramic, or clay. Pay very close attention, especially when your furnace is still new, to surprises that don't take well to heat, such as paint, paper labels, or glue. If you plan to heat some glass, clay, stones, or metal, for the sake of heating your room or warming some tea, (or chili!), then I should not have to state that these items will be HOT, and potential for burn injuries, but there it is, I just did.
One other thought that might seem overly obvious, but needs to be mentioned, is that fire requires oxygen to burn. I've tried regular clay flower pots directly over a jar candle, and the tiny hole in the bottom (or top) of the pot is not enough ventilation to keep a candle burning! If your flame snuffs out on it's own, it's probably not getting enough oxygen.
There's decorative stones in the top pottery dish - there's a close up of how that looks, at the top of this page. The bottom pottery dish adds an extra layer of non-flammable protection while also keeping the heat from dissipating so quickly.