不含大顆粒石灰石、石英、石膏及其他杂质的制磚粘土,可以用来生产飾面磚。小顆粒石灰石含量达25—30%的粘土,即泥灰岩质粘土(12—25%CaO+MgO),比不含石灰的粘土还更适用于生产飾面磚。因为用这种粘土制的坯体具有淡黃色,可以用透明的色釉复盖,用这种粘土制的坯体和釉料結合也更牢固。为了使制得的坯体具有一定的机械强度和气孔率,特別重要的是具有相当高的热膨脹系 Clay bricks without large particles of limestone, quartz, gypsum and other impurities can be used to make decorative tiles. Small clays with 25–30% limestone content, ie marlified clays (12–25% CaO+MgO), are more suitable for the production of facing tiles than lime-free clays. Because the green body made of this clay has a pale yellow color, it can be covered with a transparent colored glaze, and the clay made of this clay body and the glaze are also more firmly bonded. In order to obtain a certain body with a certain mechanical strength and porosity, it is particularly important to have a relatively high thermal expansion system.