Cutback Bitumens (liquid Bitumens) are Bitumens that are dissolved in a petroleum solvent (cutter). Typical solvents include naptha (gasoline) and kerosene. The type of solvent controls the curing time of the cutback and thus when it will obtain its ultimate strength. Rapid curing cutbacks use naptha (gasoline) while medium curing cutbacks use kerosene. The amount of cutter affects the viscosity of the cutback Bitumen. The higher the cutter content, the lower the viscosity and the more fluid it will be.