Creosotes are a complex type of chemical product having densities greater than water that are obtained industrially by the distillation of various tars, or are produced incidentally during combustion of plant-derived material (e.g., directly, from wood, or indirectly, from petroleum products); they are notably useful for their preservative and antiseptic properties. Types are produced in quantity from the burning of wood and coal in fireplaces and blast furnaces. Some creosote types were used historically as means to treat components of seagoing and outdoor wood structures to prevent rot (e.g., railroad ties and bridgework, see image), and types are commonly found inside chimney flues when the wood or coal burns incompletely, producing soot and tarry smoke. As well, creosotes are one of the complex array of chemical components responsible for the preservation and flavor of meat resulting from the process of smoking. The name is derived from the Greek kréas (κρέας), meaning “meat”, and sōtēr (σωτήρ), meaning “preserver”. The two main types in industrial production are wood-tar creosote and coal-tar creosote. The coal-tar variety, having stronger and more toxic properties, has chiefly been used as a preservative for wood, while the wood-tar variety has been used for meat preservation, wood treatment, and for medicinal purposes as an expectorant, antiseptic, astringent, anaesthetic, and laxative, though these have mostly been replaced by newer medicines. Coal-tar creosote was formerly used as an escharotic to burn malignant skin tissue and in dentistry to prevent necrosis. It is no longer used that way because of its toxic, carcinogenic properties and because better and safer treatments are now available. Varieties of creosote have also been made from both petroleum and oil shale called oil-tar creosote, when derived from the oil tar, and water-gas-tar creosote when derived from the water gas tar. Creosote also has been made from pre-coal formations such as lignite, yielding lignite-tar creosote and peat, yielding peat-tar creosote. Creosotes are commercially valuable and produced industrially on a large scale, either for direct use or as raw material for the production or extraction of various chemicals. There are several other names for such fluids, but most are not trustworthy, being regional, applying to only some variants, or to other fluids as well. For example, the term pitch oil can refer to either creosote-like fluids or kerosene.