Ivan Weiss

Stoneware

Coal oven

Coal oven

An essential part of Ivan Weiss' works were created in a coal oven, a small 2 m³ chamber located at the Royal Copenhagen Porcelain Manufactory. This oven was capable of firing ceramics at lower temperatures, around 1300 ºC, making it ideal for firing Chinese glazes such as Celadon, Olivine, and Oxblood (the bowls shown above are Oxblood). Firing in a coal oven was demanding because it had to be completely sealed before use and continuously fired with coal. The coal oven was closed in 2007 when Royal Copenhagen moved their manufactory from Frederiksberg to Glostrup.

Celadon, Olivine and Oxblood-glaze

Ivan Weiss' ceramics are distinguished by several signature glazes, including Oxblood, black and blue Olivine, and Celadon. These glazes are renowned for creating an organic texture and silky surface, primarily achieved through a firing process at about 1300 °C and slow cooling, which significantly influences the final visual expression.

Oxblood glaze contains a high concentration of copper, which produces its famous deep red color. Celadon and Olivine glazes share some essential features. Celadon glaze contains a small amount of iron, resulting in colors ranging from bluish green and olive green to brownish green. Olivine glaze, on the other hand, contains a significant amount of magnesium iron-silicates, producing green, brown, and black hues in the glaze. Oxblood glaze originates from Chinese porcelain of the Ming Dynasty (1368-1643), while Celadon and Olivine glazes date back to the Sung Dynasty (960-1279).

The three glazes have been used at the Royal Copenhagen Porcelain Manufactory from the early 1900s until the coal oven was closed in 2007. Leif Lautrup-Larsen, a chemical engineer and head of development at the Royal Copenhagen Porcelain Manufactory, describes the Oxblood glaze as follows:

"The attractiveness of Oxblood lies in the drama it produces. The flaming red surface and deepened reliefs provide a striking contrast to the bright-colored edges from where the glaze runs during firing. The green spots, created by variations in the firing temperature and reduction degree, add an additional playful expression to the glaze."

Leif Lautrup-Larsen
September 2002