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Transcript of Ceramics
Why do we wedge clay?
“I am interested in mapping the ways that popular culture – including comic books, magazines, television shows, films, and a host of other forms help to shape and change how our culture views women. Popular culture does not simply reflect women’s lives; it helps to create them and so demands critical scrutiny.”
~ Kathy King
The Ceramic Arts:
Where Does Clay
used in the studio is not a pure clay, but a mix of different clays.
◦ Igneous and metamorphic rock decompose into
called kaolin, which is most prevalent at the tops of mountains.
◦ Particles of primary clay from mountain deposits are distributed to lower regions via water ways, picking up varying levels of impurities along the way.
◦ This results in different types of
with unique characteristics that ceramicists can manipulate in their work.
Clay Body vs. Clay
Clay and Clay Body are not the same thing. Clay refers to the raw material that is dug out of the earth. The
we use in the studio is a mixture of primary and secondary clays, and other materials that have gone through various methods of processing.
Magnified View of Clay Platelets
Three Common Types of Clay body:
Porcelain - has fewer impurities than other types of clay body but is less
and more difficult to work with.
Stoneware - contains more impurities than porcelain, including iron.
Earthenware - is the least pure of the clay bodies, most often found in creek beds.
The "purity" and characteristics of a clay are determined by how far it has traveled from it's source.
Clay is composed of microscopic, disc-like particles called
To remove air pockets
To remove excess moisture
To ensure that clay has a uniform consistency
There are two basic methods for wedging clay,
Narratives on Clay:
Early Greek and Moche Pottery
Throughout history, cultures like the Ancient Greeks and the Moche people of Peru, have used surface design on ceramic objects to record important aspects of their social, historical, and religious lives.
Heracles Stabbing Nessos, the Nessos Painter, 630-620 B.C.
Achilles and Ajax Playing a Board Game, Exekias, 540-530 B.C.
Hunt Bottle, Moche, 4th-7th Century
Stirrup Spout Bottle with Warriors, Moche, 4th-7th Century
is what transforms soft clay into durable ceramic.
Another major constituent of clay and clay dust is silica. Breathing in the silica in clay dust is hazardous. Always wipe down tables twice when cleaning the studio, and always wear a dust mask when cleaning up clay dust.
Different types of firing:
- Pottery is fired in a pit or bonfire, usually at a lower temperature.
- Pottery is fired in an enclosed structure that is capable of achieving very high temperatures and provides a greater level of control than open firing.
- The initial firing which changes clay into ceramic, or from greenware to bisqueware, at least
- The final firing in which pottery has been painted with glaze, then fired to create a glass like finish which acts a seal. The resulting pottery is called glazeware, at least
As the organic materials in clay burn up during the firing process, toxic fumes are released. Kilns should be properly ventilated to avoid health hazards.
Clay vs. Ceramic
refers to a compound made of inorganic materials that have been hardened by the application of extreme heat. Usually by firing in a kiln.
Clay is a naturally occurring compound composed of organic
inorganic compounds, including various clay minerals and metal oxides.
: Cones and Temperature
To get the right results in firing, ceramic items are fired to specific temperature ranges, or
. In the studio we will typically fire as low as
, but no higher than
05 = 1870 to 1911
04 = 1915 to 1971
03 = 1960 to 2019
02 =1972 to 2052
01 = 1999 to 2080
1 = 2028 to 2109
2 = 2034 to 2127
3 = 2039 to 2138
4 = 2086 to 2161
5 = 2118 to 2205
Firing Temperatures (degrees F):
Glazing not only makes ceramic items more decorative, it also creates a seal that makes them water tight. When fired, ceramic glaze melts to form a glass-like layer on the surface of a pot.
There are 3 main ingredients in glaze:
- the glassing agent in glaze, silica, which might come in the form of sand, quartz, or ground up glass
- a refractory agent that lowers the melting point of a glaze, allowing glass to form at lower temperatures
- helps to create a bond between the glaze particles and the surface of a pot
Types of Glaze
The properties and purpose of different glazes vary depending on the ratio of frit, flux, and clay they contain.
- contains a higher amount of frit and clay than flux, allowing designs to be painted without colors melting into each other.
High Fire Glaze
- Contains more frit than flux, which allows it to withstand higher firing temperatures.
Low Fire Glaze
- contains a higher amount flux than it does frit and clay, allowing glass to form at lower temperatures, which reduces shrinkage and warping of ceramic wares.
In addition to fluxes and frits, various
can be added to glaze as colorants. For example, depending on whether it is used in high fire or low fire glaze, and what other additives are present, the addition of copper can result in either red, green, or turquoise.