Clinker is the main component that determines the main final properties of the future massive slab. After firing the raw material at a certain temperature, the materials are formed to obtain granular grains with a diameter of 1-5 cm. Special furnaces are used for heat treatment. This stage is the most energy-intensive and labor-intensive of all production stages, starting with the production of cement. Ashless fuel oil or natural gas is used to burn clinker. The firing temperature of low-iron clinker made of white Portland cement is high and reaches 1450-1500 ° C.  Physicochemical processes occurring during heating of the raw mixture used to obtain white Portland cement do not differ from the processes typical for gray Portland cement. Due to the nature of the raw material mixture and the additives introduced into the gas environment in the kiln, there can be only slight differences in the physical and chemical processes. When grinding clinker, additives are added: gypsum to regulate the installation time, up to 15% of active mineral additives (pyrite slag, blast furnace dust, bauxite, sand) to improve some of the properties of cement and reduce cost. Raw materials are fired at temperatures from +1450 to + 1480 ° C.