The percentage of sand in clay-powder is up to 15 %. Usage The advisable volumetric ratio of clay-powder - sand - water for building of fireplaces is 1: 2,5: 0,7. At first mix clay-powder and sand. After pour water and mix until homogeneous. The advisable volumetric ratio of clay-powder - sand - water for building of mouth of an oven is 1:1,5:0,5. It is advisable to put a part of 0,05 fireproof cement of total volume to this mixture. At first mix clay-powder, sand and cement after pour water and mix until homogeneous. It is possible to use dust of fire clay (fraction 0-1 mm) instead of sand for preparing the building mass for fireplaces.