Zao Xin Tu

Zao Xin Tu (literally 'stove-heart earth'), also called Fu Long Gan, is the yellowish-brown to reddish-brown earthen material taken from the inner lining of traditional Chinese wood- or straw-burning cooking stoves, where it has been baked and hardened by years of continuous fire directly beneath the cooking pot. Chemically it consists largely of silicates and aluminum oxides with iron oxides and alkaline earth carbonates, modified by long heating. The material is pried from the stove, the charred outer surface scraped off, and the inner baked clay broken into chunks. In traditional Chinese medicine, Zao Xin Tu is acrid and warm, entering the spleen and stomach channels; it warms the middle burner, harmonizes the stomach, stops vomiting and bleeding, used particularly for cold-pattern vomiting in pregnancy, chronic diarrhea from spleen deficiency, and bleeding from the upper or lower digestive tract due to deficiency cold. It is typically decocted first, with the strained liquid used to cook other herbs.