Bockhorn clinker paving stones enjoy well-deserved popularity not only in their homeland in Germany, but throughout Europe, including Russia. Excellent quality, wide range of colors, reasonable price - all these advantages are successfully combined in the products of the plant from the city of Bokhorn, in Lower Saxony. Officially, the Germans trace the history of the enterprise since 1906, when the already operating manufactory was bought by Heinrich Ulhorn, Wilhelm Müller and Dietrich Schmidt. Until the 1960s, the plant used ring kilns that were fired with peat, then they were replaced with gas tunnel kilns, which raised production to a new level.
Surprisingly, in Russia the quality of clinker paving stones from Bockhorn was paid close attention earlier than in Germany. The book "Production of bricks and other clay building materials" was published in 1900. Its author Ivan Grigorievich Malyuga is a professor at the Nikolaev Engineering Academy in St. Petersburg, a chemical technologist who was one of the founders of the International Society for Testing Materials. The book contains a very interesting overview of clinker products intended for paving sidewalks and streets.
According to the author, clinker paving has become widespread in Holland since the beginning of the 19th century due to the lack of natural stones. Towards the end of the century, road clinker was also produced in Germany, England and the USA. "The material for clinker in the village of Bockhorn near Neuenburg in Oldenburg is very famous," Ivan Malyuga especially notes and gives the exact composition of the clay: 70.22% silica, 13.67% alumina, 6.8% iron oxide, 1.3% magnesia, 3.37% alkali, 5.3% water. It is the correct ratio of ingredients that allows you to achieve maximum water resistance and hardness of products.
The author describes in detail the features and differences of clinker slabs, depending on their purpose. Sidewalk stone is mainly subjected to "the action of erasing forces" and its thickness is not particularly important (30-50 mm is enough), horizontal dimensions for uniformity of high-temperature firing, as a rule, are less than standard brick ones: 160-220 mm. As for the paving stone, according to the author of the book, clinker, due to its fragility, is inferior to natural granite, porphyry, and basalt. “However, as we already know, in Oldenburg and Holland, in the absence of stone, it is very common to pave streets and roads with clinker,” says Ivan Malyuga. Thinking about the optimal dimensions, he comes to the conclusion that they can be the smaller, the stronger the base of the road and the harder the stone itself. "Thus, the Oldenburg clinker paving stone (from Bockhorn) usually has the following format: 22 cm long, 5-5.5 cm wide and 10.5-11 cm high."
Of course, a lot has changed since then. Gone are such significant dimensional tolerances. Modern clinker in terms of the quality of firing, selection of composition, strength, and appearance is much superior to the stone from Bokhorn, which was studied and considered practically standard by a Russian scientist more than a hundred years ago. But if you walk through the streets of old German cities, you will probably find a masonry that survived two world wars and was created at a factory that has been operating under the Bockhorn brand since 1906.
