Goerg & Schneider Clay 933 – Stoneware Spot Clay, 20 % Grog 0–0.2 mm

Goerg & Schneider Clay 933 – stoneware with basalt spots for throwing and hand-building

Clay 933 from Goerg & Schneider is a plastic stoneware clay with 20 % grog (grain size 0–0.2 mm) and dark basalt spots. You can throw it on the wheel, build vessels by hand, or press or cut it. According to the manufacturer, it suits small pieces as well as larger ones.

The fine grog makes the clay easy to shape and keeps it stable while you work. It suits cups, bowls, vases, plant pots and decorative objects. The clay fires between 1000 and 1240 °C. The higher you fire, the more clearly the spots show. They are visible unglazed and under transparent or semi-transparent glazes.

Fired colour and shrinkage

The fired colour depends on the temperature. Firing shrinkage and water absorption show how dense the clay becomes at each temperature. At 1240 °C, water absorption is only approx. 0.5 % according to the manufacturer. At 1070 °C it is still 9 %. Allow for shrinkage when sizing your pieces: drying and firing together produce a noticeably smaller piece than the unfired blank.

• 1140 °C: light cream with spots
• 1200 °C: leather with spots
• 1240 °C: cork with clearly visible spots

Working the clay

Thanks to the fine grain, throwing and hand-building work well even for details. Let the blanks dry slowly and evenly, especially with thick walls, so that no drying cracks form. Seal opened clay airtight so that it does not dry out. A test piece with your glaze will show you beforehand how glaze and spots work together.

Goerg & Schneider Clay 933 product details

• Manufacturer: Goerg & Schneider, clay 933 (leather spot clay)
• Type: plastic stoneware clay with dark basalt spots
• Grog content: 20 %
• Grog grain size: 0–0.2 mm
• Firing range: 1000–1240 °C
• Fired colour: light cream to leather and cork, depending on temperature
• Drying shrinkage: approx. 8 % (measured at 110 °C according to the manufacturer)
• Firing shrinkage: 1070 °C 4 %, 1140 °C 6 %, 1200 °C 8 %, 1240 °C 7 %
• Water absorption: 1070 °C 9 %, 1140 °C 5 %, 1200 °C 2 %, 1240 °C 0.5 %
• Coefficient of thermal expansion (20–500 °C, fired at 1240 °C): 61 × 10⁻⁷ °C⁻¹
• Use: throwing, hand-building, pressing/cutting

You will also need: a kiln for temperatures above 1000 °C (a domestic oven is only suitable for drying); glaze of your choice