• FA-123715 © Technisches Museum Wien, Photo: Peter Sedlaczek
  • FA-123716 © Technisches Museum Wien, Photo: Peter Sedlaczek
  • FA-123714 © Technisches Museum Wien, Photo: Peter Sedlaczek
  • FA-123719 © Technisches Museum Wien, Photo: Peter Sedlaczek
  • FA-123726 © Technisches Museum Wien, Photo: Peter Sedlaczek
  • FA-123726 © Technisches Museum Wien, Photo: Peter Sedlaczek
Collection Area
Production Technology
Glass and Ceramics
1920 - 1929
At the moment this object is not published in the museum.

Cup shapes displaying glazing techniques, Vienna, 1929


In simple terms, stoneware is actually ‘ware’ that is made from stoneware clay and is non-porous, i.e. impermeable to water. By contrast, earthenware is actually pottery that is porous, i.e. permeable to water, and has to be glazed to make it watertight. And glazing is what this article is all about.

Glazing is a vitreous surface finish used for ceramics. It creates a smooth, fused coating that is watertight. Depending on the raw material and the firing temperature, the ceramics produced are characterised by a high-fired (stoneware, porcelain) or low-fired (earthenware) body. Porous ceramics only become watertight once they have been glazed, but some high-fired ceramics are also glazed to smooth their surface or give them a particular colour tone.

So glazes have both a utilitarian and an aesthetic purpose. They consist of a mix of powdered minerals which, after firing, forms a vitreous coating that binds with the ceramic body. Different metal oxides produce different colour tones.

What this amounts to in practice is demonstrated by a small lot of ‘24 cup shapes designed for the purposes of displaying glazing techniques’, which was gifted to the Technisches Museum Wien in 1929 by the well-known Viennese ceramicist Michael Powolny. Here Powolny experimented with identical glazes on different underlying surfaces and produced all manner of colour tones by mixing various metal oxides.

For instance he used a colourless transparent glaze both on Kirchdorf clay (from near Krems in Lower Austria, Fig. 1) and red Viennese clay (Fig. 2). He also initially applied an opaque (i.e. non-transparent) white tin glaze to red Viennese clay (Fig. 3) before displaying it on Kirchdorf clay coloured green using copper oxide and lead chromate (Fig. 4) and cobalt blue using copper carbonate (Fig. 5). A black colour tone can also be obtained using the same white tin glaze coloured with manganese, copper and iron oxide (Fig. 6).

How do we know all this? By hoping that, over the decades, the labels enclosed with the cups were not been mixed up…

Manufacturer: Michael Powolny, Vienna
Production date: 1929

Inv.Nr. 11639/1
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