Cutback Bitumen is made by reducing the viscosity of and ordinary bitumen by adding mostly petroleum type solvent. Cutback Bitumen are used because their viscosity is lower than that of neat asphalt and can thus be used in low temperature applications. After a cutback is applied the solvent evaporates away and only the Bitumen is left. A cutback bitumen is said to cure as the petroleum solvent evaporates. Cutback bitumen are typically used as prime coats and tack coats. Generally Cutback Bitumen are divided into three groups depending on their volatility of the solvent added: