Alkali hydroxides, NaOH and KOH, arise from the direct dissolution of and oxides produced by the pyrolysis of the raw materials at high temperature (1450 °C) in the cement kiln. The presence of minerals with high Na and K contents in the raw materials can thus be problematic. The ancient wet manufacturing process of cement, consuming more energy (water evaporation) that the modern dry process, had the advantage to eliminate much of the soluble Na and K salts present in the raw material.