MYSTERIOUS ARCANUM - PART I

One of the best kept secrets of the Meissen Manufactory was the knowledge of the Arcanum, the secret of making the porcelain. The founding of the factory itself at the Albrecht Castle in Meissen was mainly done to separate the processes of material preparation, designing and firing locally from each other to prevent the revealing of the secret.
Besides Böttger initially only two "Arcanists", Jacob Bartholmäi and Heinrich Wilhelm Nehmitz, knew the secret, the one was initiated into the science of the compound and the other in the preparation of the glaze. Even so the secret was taken into the world by the getaway of Samuel Stölzel, one of the closest associates of Böttger, to Vienna and since 1719 manufacturing of the porcelain could be done as well by the famous Vienna Manufactory.
What is this European porcelain, whose invention and development required so much effort, eventually made of? Porcelain is a sintered ceramic material. The in Europe most widely produced hard-paste porcelain is made of a mixture of 50% kaolin, 25% quartz and 25% feldspar and is burned with a temperature of 1350°-1460°C . The kaolinite mineral results from the weathering of feldspathic rocks. The feldspar as a flux assists the sintering of the mass, but is also responsible for the firing shrinkage. The quartz in turn reduces the plasticity of the mass, but decreases the internal loss and increased the fusibility.
The material preparation includes crushing, cleaning, mixing and aeration of the raw material mixture. The hard rocks of quartz and feldspar are grinded finely in tumbling mills, the soft kaolin is scoured in water, screened (the iron removed by magnets) and the clean mud then is drained of. Thereafter the final mass is placed in the desired shape on the wheel by using stencils or poured into plaster molds.