The delivered clay is placed in an internal store, sufficient for a full weeks production and is scraped and belt fed through a feed hopper into the mixer, where manganese or lime is added (to enhance the colour), as well as water to prevent dust-forming during the mixing process. Although no part of the factory is dusty, good housekeeping and modern extraction systems ensure that all areas remain as dust-free as possible. On leaving the mixer, the clay mixture proceeds to the pug mill, which is a sort of large grinder with a mill race comprising apertures, which crushes any stones or pebbles present. The clay exits the pug mill through these apertures, in the form of little ‘slugs’ approx. 18 mm in diameter. These slugs are then passed through a rolling mill with a1.0 mm opening. A conveyor belt transports the rolled lumps of clay to the clay cellar.
De Rijswaard is one of only two brick factories in the Netherlands with their own clay cellar. Here, the pre-processed lumps of clay are stored once more, layer by layer, with a view to promoting further consistency of the raw material. The clay is ultimately sliced off diagonally using a dredger. It is automatically transported from the clay cellar to the brick press.