The loss on ignition of a raw material, cement or a clinker sample is the amount of weight lost through raising the temperature of the material to a predetermined level. As an indicator it can be used to monitor and improve the quality of the final product.

Weight loss during heating can be due to the evaporation or volatilisation of a variety of components of the sample. Water is lost at 100-105˚C, organic material is burned off at about 550˚C and most of the carbonates can be lost between 800- 1000˚C.