Charcoal is a light, black residue of carbon left when wood, or other plant or animal matter, is heated strongly with little oxygen so that its water and volatile substances are driven off. Traditionally the heat came from burning part of the wood itself, stacked in a kiln or a conical pile; modern makers carbonise wood in closed retorts. Demand for it long drove deforestation, as in central Europe. It has fuelled forges and iron smelting, cooking and heating, and has been ground for black pigment and for black powder, while activated charcoal is used in poison control. In incense it plays two parts. Resins such as frankincense and myrrh do not burn on their own and are traditionally heated on charcoal or glowing embers, while powdered charcoal is the fuel of many self-burning incenses, kept smouldering by a nitrate oxidiser, and goes into the paste on Indian stick incense. Cunningham sets loose, granular incense on a lit charcoal block in a censer or a dish half-filled with salt or sand, sprinkling on a little every few minutes; he also burns essential oils on charcoal blocks, and pours powdered jet on a glowing block so that its fumes can be used for scrying. In Hoodoo a small bag of salt and charcoal was carried for protection against evil spirits, and charcoal is among the empowering medicines placed in the Kongo-derived minkisi bundles that archaeologists found in a house in Annapolis, Maryland.