The loam in the Kesselt Tableland is the so-called loess. Loess actually means loose soil, and is a deposit of very fine soil transported by the wind from North Germany during the last glacial period. The material is easy to work with and ideal for manufacturing hand-moulded bricks. The quarry is located behind the plant. It contains various deposits of loess: grey, yellow, pink and red.
The deposits are quarried when needed, and conveyed directly into the plant. The clay is processed in its pure state. Minerals and chemicals are rarely added and only when required, for example to make manganese bricks. Conveyor belts transport the clay in the appropriate proportions from the depositors to the mixers. The addition of water is closely monitored to optimise the clay's plasticity. The loam deposits are dispensed and mixed at this stage.
The old brick makers pressed the sand faced clay galls in a mould. After the excess clay was wiped off, the mould was turned and lifted off the wet brick. At Nelissen, we use identical procedures to make lug bricks, the so-called "specials".
With the exception of the specials, the manufacturing process for hand-moulded bricks is currently fully automated. State-of-the-art machinery fully imitates the procedures used by craftsmen in the past. Each move and each operation are important. In addition, the equipment is designed in such a way that 8 different hues can be produced simultaneously. Craftsmanship is applied throughout the process to create the typical bricks with irregular surfaces and a variety of hues and grain.The water used to make the bricks must evaporate completely and the process used takes place in computer-driven dryers with customised programs depending on the type of clay and the size of the bricks. The drying process must be fast and uniform. Depending on the thickness of the bricks, the unfired bricks are ready to go in the kilns after 24 to 48 hours. The automated process stacks the dried bricks into the bogies of the moving hearth furnace in predefined patterns.
The firing process is vital and defines the quality of the bricks. Nelissen uses fully-automated kilns designed using state-of-the-art technologies. The settings of the kiln are permanently monitored, and every move of the process is recorded in a log. The firing of the bricks takes 3 days in a kiln of over 100 meters long by 7 meters wide. The computer monitors the firing cycles and the conditions in the kiln providing the capability to create over 25 warm and diverse hues. Correct timing of the significant investments has enabled Nelissen to expand steadily. With an annual production capacity of 150 million bricks, Nelissen has become an important player in the European market.