A little lesson on the subject of porcelain

The seven most important things we should know about Porcelain:

 

  1. term Porcelain is derived from the Italian name for cowrie snails ("porcellana")
  2. Around 620 AD The manufacturing process of porcelain in China was developed
  3. Around 1300 AD, Marco Polo brought the first porcelain from China to Europe (Italy)
  4. Porcelain consists of kaolin, feldspar and quartz (depending on the proportion of the constituents, hard or soft porcelain is obtained); other materials and mixing ratios are the trade secret of every manufactory
  5. Porcelain differs from ceramics in its sintering behavior (semi-transparency of porcelain)
  6. Characteristics of porcelain:
    • has a dense body (burned clay)
    • mussel break
    • great hardness
    • bright sound
    • is acid and alkali resistant
    • more or less transparent (depending on thickness)
    • good insulation against electricity
    • poor thermal conductivity
  7. Porcelain production:
    • Porcelain mixture is liquefied and poured into hollow plaster molds consisting of at least two parts - gypsum molds remove water from liquid mass - mass settles on inner wall of mold until desired thickness is achieved - remaining mass is poured off - plaster molds rest - blank are taken out of mold , dried and deburred - further components (eg Henkel) are glued on; new processes and technologies nowadays (for example injection molding)
    • 1st firing = biscuit firing (at 900 ° C - 1000 ° C) takes 18-20 hours; Result: still fragile, rose-colored porcelain form
    • In the subsequent glaze, color bodies, engobes (clay slips) or metal salts are applied as a top, interior or underglaze decoration
    • 2nd firing = smooth firing (at 1100 ° C - 1480 ° C) takes about 30 hours; Glaze melts and covers rosé-colored porcelain with outer skin (in addition, a "shrinking" of the form to note = peculiarity of porcelain production); Result: ready-to-use porcelain in white or with underglaze
    • Further decorations by spray technique, hand painting, application of adhesive films or precious metals
    • Further firing processes depend on the type of decor (decorative firing at approx. 850 ° C)