Set three or four large chunks of hardwood ablaze in your fire pit. Hardwood varieties that are spiritually relevant include holly, oak and eucalyptus among many others. Burn the wood for about 10 minutes. This gives it time to become charred without burning into white, glowing embers.
Dowse the fire with three gallons of water to put it out. Chop enough blackened, burned wood from the smoking remains to fill a measuring cup. Use a spatula or similar item so as not to burn your hands.
Add the chunk of blackened hardwood to the cauldron or cast-iron skillet. Introduce the salt to the pan. Salt is a universally used item in witchcraft, as a cleansing agent and purifying material.
Chop at the charred chunk of wood, which should crumble into little more than black ash-powder. Mix it in with the salt, using the cauldron and spatula as a sort of mortar and pestle.
Pour the finished black powder into a jar for safe-keeping.