Candles

 Candles were used as a replacement for oil lamps, which used plant oil or animal fat.

To make an oil lampwork a sting or wick was lit on fire and put in a shallow dish and the oil would combust to make a fire.

Last time it was fatty acids now it is waxing, called exothermic, the wick in candles is not what is burning, it is the oil that is being drawn up by the wick.

Oil lamps are just dishes of flammable oil with cotton in it, if you accidentally bump into it and then welp you got a fire in your house, the reason why candles were so good is that they turned the fuel into its own fire.

If you build the wick and the fuel correctly in a solid state you can make it so that when the flame at the top burns it burns the wax next to it will melt and will be taken up by the wick to combust causing it to light its fire