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 homogeneous mixture of accurately predetermined proportions of manganese oxide with grey-red baking loam is responsible for the black colour of the brick. The colour ranges from mainly charcoal grey to pitch-black, with brown and blue shades.
The colours shown are a near reflection of reality.