Station: [3] Stoneware, Earthenware, Engobe-decorated Pottery

Bürgel pottery falls into three major product categories: stoneware, earthenware and engobe-decorated pottery. But what’s the difference?

Stoneware refers to clay pots that are fired at very high temperatures – around 13 hundred degrees Celsius. At that temperature, the clay goes through a process called sintering, in other words, its components fuse. The resulting pot is water-tight after firing and doesn’t need to be glazed. The exceptionally high quality of the local clay means that Bürgel stoneware can be produced with especially thin walls.

Bürgel stoneware also stands out due to a special design feature. During the firing process, a mixture of ground cobalt glass, salt and litharge – a type of lead oxide – are tossed through the fire into the kiln chamber. The mixture condenses on to any pots it touches and forms an irregular area of bright blue glaze …

… known as the “blue apron” – the trademark of Bürgel stoneware.

“The local unglazed pots do not merely permit vinegary substances to be boiled for several hours, and pickles to be stored for years. One can also dissolve and process all salts in them and keep these for several months. One can use them to store sulphur salt, saltpetre and acids, and also boil up phosphoric acid in them, without the pots suffering in the least or being apt to leak.”

An enthusiastic apothecary talking about Bürgel pottery in 1810. No wonder that fermentation vessels, distillation flasks and large storage containers were made of stoneware until well into the 19th century!

Earthenware, the second product category, is fired at lower temperatures. The fired clay – or bisque – remains porous and has to be glazed, and thus rendered water-tight, in a second process. For a long time, the preferred slip glazes were based on iron oxide and were brownish in colour. But in the 19th century, people gained a better insight into chemical processes and had access to a larger selection of raw materials.….

… and the result was Bunte Ware – which translates as coloured ware – with a range of different decorations; in Bürgel, mainly small floral and dot patterns. The coloured patterns were applied with what’s known as a slip cup. These resemble small oil lamps with a quill that serves as a spout. 

Filled with dyed liquid clay known as “engobe”, these slip cups are wielded almost like a fountain pen traced across the clay pots. After being decorated, the pot still needs to be sealed with a clear glaze and fired to make it waterproof."

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Zitat nach: Bürgeler Keramik. Eine Darstellung der Geschichte des Bürgeler Töpferhandwerks anhand der Sammlung des Keramik-Museums, S. 22.