Creosote is a type of preservative that is used to protect wood from decay and insect damage. It is derived from a variety of sources, including TAR, oil, and coal TAR. TAR is a dark, viscous liquid that is produced by the destructive distillation of organic materials such as wood or coal. OILY substances are liquids that contain hydrocarbons and are derived from petroleum or other natural sources. Coal TAR is a thick, black liquid that is produced when coal is heated in the absence of air. All three of these substances can be used as a source of creosote.