The facade bricks (non-perforated) have five sand covered sides and one side with possible oblong groove. The structure looks rugged with fine and irregular grooves in the sandy surface. The baking process takes place in a gas-heated tunnel oven under slightly reduced atmosphere.
The colour of this dark brick varies from mainly anthracite to coal black, with blue and brown nuances and white deposits visible. The ageing process also influences the colour shades.
The colours shown are a near reflection of reality.