an introduction to ceramics the science of clay:
TRANSCRIPT
DehydrationDehydration• Leather hard- beginning of
dehydration process; stiff but moist
• Bone Dry- green ware; next step in dehydration process; water has evaporated; unfired; hard but fragile
• Kiln- enclosed heat source in which clay is fired (heated).
• Dehydration process is essentially complete at about 500° C when the chemically combined water is driven out of the clay in the kiln.
VitrificationVitrification• Bisque; early stages of
vitrification; clay is still porous; ready to glaze.
• Vitreous- the pottery will no longer absorb water chemically and can never return to its original plastic state.
• Bisque fire- bone dry clay fired at low temperature to bisque; early stages of vitrification; clay is still porous; ready to glaze.
History of PotteryHistory of Pottery• Pot making dates to about
10,000 BC in parts of Asia
• Pinch or coil technique
• Pit firing
• Utilitarian
• All of the earliest work was earthenware with no glaze
BurnishingBurnishing• One of first surface techniques
• Functional
• Aided in the retention of water, but did not vitrify completely
• Rub with smooth object at leather hard stage
• Time consuming – usually takes at least three burnishings
GlazeGlaze
• Silica
• Forms a glass coating
• Glaze fire- fire after glaze is applied to bisque ware. Glaze is non-porous after firing.
• The earliest known glazes are found in the Nile valley about 5,000 bc
• High temperature ceramics; stoneware, porcelain, glazes, were developed by the Chinese about 2000 years before the rest of the world
• Potters Wheels are known to have been used in the Indus valley (Pakistan and northern India) about 4,000 BC but possibly earlier
• True potters wheels appeared around 3000 BC in several areas of the middle east and China
Slip, Score, and CoilSlip, Score, and Coil• Technique used to attach pieces of clay
together• Scoring- scratching the surface of the
clay• Slipping- adding water or liquid clay to
scored surface• Put slipped and scored surfaces
together • Coiling- add small coil (tube) of clay
around slipped and scored edges and smooth to reinforce connection