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 a precise proportion of manganese dioxide in the clay results in a light grey brick. The different types of sand provide colours that vary from white to grey, interspersed with light grey and dark shades in defined proportions, in which the white deposits are clearly present. Through sintering Nelissen obtains the light grey brick with black and brown spots.
The colours shown are a near reflection of reality.