The clinker's history
In one of the last ring kilns in northern Germany, the traditional Rusch brick factory has been burning traditional clinker bricks for generations. Located directly on the Elbe, they extract their clay raw material in the immediate vicinity of the Elbe glacial valley..
The profession of brickmaker was not uncommon, at least the relatively common surname testifies to it and the still ubiquitous street names that denoted the former location of a brickworks. The brickwork trade had its heyday during the building booms of the late 19th and 20th centuries and is now a dying profession. Even the clinker-crazed seventies and eighties didn't give him any notable upswing. What was built back then – and still used far too often today – is mostly of the cheapest quality, from machine mass production. Mostly produced without love, sometimes without expertise and in extreme cases even without clay as a raw material. And, tragically, often at the other end of the world, where brick facades are completely unknown.
Craft vs. mass-produced goods
So what distinguishes Rusch's handcrafted clinker bricks from industrial mass-produced goods? The aesthetic added value of these high-quality bricks is not only noticeable to the technically or architecturally trained eye. Every clinker is unique, and so every single clinker is handled many times during production until it is sorted onto the pallet in perfect quality: The color spectrum of the freshly burned clinker ranges from a sandy yellow to various shades of red to a iridescent blue-black. This play of colors comes about through the color of the aggregate, through the firing with coal and through the burning process, since in the ovens fired with hard coal and wood the temperature is not the same everywhere.
From earth and water
The craft of the brickmaker is a trade that works with the four natural elements more than almost any other: an interplay of earth, water, air and fire.
First, the most important raw material, clay, is ground in the so-called pan grinder, mixed with sand and water and shaped in an extruder in such a way that the clinker - the bricks - can be cut from it. And the last two elements are also important: the air that dries the blanks and the fire for the good branding. There is one more thing: time. It used to take three months to make a brick – eight weeks just to dry. In the meantime, the Rusch brickworks has significantly shortened the production process to just under a week by using industrial drying chambers. To operate it, it draws its energy from a combined heat and power plant, which it feeds with renewable raw materials.
The finish: the fire
However, the lion's share of the production time is taken up by the firing process these days: The dried blanks are placed in the walk-in ring kiln. The "oven door" consists of two brick walls that are bricked into the door opening for each fire. The clinker bricks are burned for 16 days, during which time the kilns are constantly monitored by hand – day and night – and fed with fuel. Only after this long burning time is the furnace door opened again. Always nice and slowly to avoid cracking when the bricks cool down.
Incidentally, clinker differs from so-called bricks in that it burns at a high temperature of 1200 °C. Bricks absorb water and are therefore not suitable for weathered facades. With real clinkers, on the other hand, the high temperature creates a dense surface that is called "sintered". The pores close as a result of the sintering. A water-repellent layer is created, which makes the clinker usable for unplastered facades.