Hardwood Ash from a Clean Fire Lit by Bow Drill

Wood ash is what is left when wood burns: mostly calcium carbonate, with some potash and carbon. Burn clean hardwood right down in a stone-ringed pit, lit from a bow-drill ember, and sieve the cold ash. It is the start of lye, soap, potash and ash glazes; wood gives about 6 to 10 % of its weight as ash. The picture: white wood ash in a stone fire ring.