Bai Cao Shuang

Bai Cao Shuang ('hundred herbs frost') is not a plant but a processed mineral-organic substance: the fine, light, sooty deposit scraped from the underside of chimneys, stove-tops, and cooking-pot bottoms after the prolonged burning of grasses, straw, weeds, and miscellaneous herbaceous fuel. Traditionally collected from rural earthen or brick stoves, the soot is a black, weightless powder consisting largely of amorphous carbon together with condensed pyrolysis residues of the burnt plant material. It is sieved free of grit before use. In Chinese medicine it is administered internally to stop bleeding (haematemesis, epistaxis, uterine bleeding) and used externally on sores and ulcers; modern preparations are rare because of the changing technology of domestic cooking.