Stoneware is the name for ceramic masses of the class sintered ware , the shards of which burn tightly or vitrify or sinter when fired . It is not translucent and is linguistically often confused with earthenware , which belongs to the class Earthenware , due to the same determinative word .
|Ceramics||Class: sintered products||Subclass: stoneware||
Along with porcelain, stoneware belongs to the sintered ware class . Both products have in common that high purity clays with a high aluminum oxide content are used as the starting material . Due to the fact that there is almost no iron oxide content, porcelain remains white even after the fire and translucent if the body is thin.
The predominantly gray body is created by a reducing firing atmosphere. Stoneware is impermeable to water even without glaze , but has a rough surface. Without glaze, it can be grinded , cut and polished like stone . A well-known early example of this is Böttger stoneware .
A technically simpler process of surface smoothing is the application of glazes. With stoneware, these can be created by adding table salt at a later stage of the firing process. The sodium contained creates a layer of sodium-aluminum-silicate on the surface, which melts at the oven temperatures. For handicraft purposes, metal salts of cobalt, manganese or iron can also be added to the glazes and several firing steps can be combined.
The strength parameter, which is essential for technical applications, is determined not only by the material but also by the thermal process control of the sintering . This also includes the rapid lowering of the material temperature at the end of the firing process ( lintel cooling ), with which the microstructure is frozen and undesired crystallization processes are suppressed. In contrast, the surface can be designed with glazes by specifically maintaining certain temperatures and setting redox atmospheres .
Stoneware is expensive due to the high energy consumption and the special raw materials. Therefore, its use was oriented either to luxury needs or to its special material properties. The generation was only possible by combining several technical areas of knowledge. At the same time, the high final price made it possible for particularly skilled craftsmen to work in all process stages. After the material was probably discovered while smelting metal, the knowledge of the furnace construction was transferred to the special furnaces for the high temperatures. During the manufacture of the ceramic articles, thin-walled and complex vessels were quickly created, which testified to a high level of craftsmanship. In addition, there were elaborate decorations using glazes, elaborated or applied relief designs and applied decorations such as small pieces of quartz.
In addition to this need for luxury, there were practical applications due to the high chemical resistance, the high melting point and the great strength.
For the preservation of food, the resistance to acids, aqueous alkalis and salt was ideal compared to common lead-based glazes. For the pharmaceutical industry and the manufacture of chemical equipment, it was often more suitable than the relatively soft and low-melting glasses. Also, dairy products , beverages such as beer or the popular Sauerbrunnen were traded in stoneware bottles.
With the development of industrialization in the 19th In the 19th century, the application increasingly shifted to economic areas. In addition to chemical equipment and apparatus, stoneware was also discovered as a building material. It is used as fine ceramic floor tiles and fine stoneware , for downpipes in the sanitary area and as underground sewer pipes . In the household sector it has been almost completely replaced by porcelain.
Stoneware was made in China and Japan over a thousand years ago . Many vessels are covered with a greenish celadon glaze. In Germany, stoneware was developed in Siegburg around 1300 and subsequently manufactured in numerous German ( Aachen , Raeren , Langerwehe , Frechen , Cologne , Waldenburg , Westerwald , Peterskirchen ), English and French pottery locations and regions. In the 16th and 17th In the 19th century, stoneware reached its artistic peak through relief layers that were produced using matrices based on graphic templates. In Raeren and the Westerwald, cylinder belly mugs were mainly made with picture overlays, including the legend of Susanne and the prince electors. In Siegburg, the potters around the Knütgen family produced Schnellen , cylindrical drinking jugs with rectangular supports. Here, too, mythological and religious themes predominate. The most famous product from Frechen was the so-called Bartmann mug .
From the early 16th In the 19th century and especially around 1580/90, numerous potters from the Rhineland (Raeren, Siegburg) migrated to the Westerwald , after which this part became known as Kannenbäckerland . There the pottery trade experienced a further boom with salt-glazed blue-gray goods.
The blue-gray stoneware vessels came in the 19th and 20th centuries. Century mainly in the agricultural dairy industry, in the storage and as household utensils. They were also used to fill food (vinegar, oil or mustard), ointments or pharmaceutical essences. Also in chemistry in the 19th In the 19th century, stoneware vessels were popular because of their acid resistance, before they were replaced by glass vessels. Very large stoneware containers, which were mounted on pot wagons , were even used for rail transport , as acid-proof metal tank wagons were not yet available. Before glass mugs were introduced at the Oktoberfest , millions of beer mugs ( Keferloher ) were produced every year especially for the Munich spectacle.
The quantitatively almost equally important stoneware production in Saxony is already in its 14th Century back. In the first half of the 15th In the 19th century, the highest artistic quality ceramics of the European Middle Ages was produced in Bautzen . Other important pottery places were Dippoldiswalde , Hohenleipisch , Muskau , Schmiedeberg , Waldenburg and Bunzlau .
→ Main article German stoneware
- Search for stoneware in the German Digital Library
- Homepage of five museums on Rhenish ceramics
- Website of the antiques dealer Vogt