Here is a quick 101 on clay:
d e f i n i t i o n s
C L A Y
A naturally occurring inorganic substance composed of very small "plate- like" particles.
C L A Y B O D Y
A mixture of clay and various compounds used by ceramicists to achieve varying characteristics of final ceramic objects. Various compounds include feldspars, silica, alumina, kaolins.
C E R A M I C
A clay object stabilized through the application of heat.
P O R C E L A I N
A type of clay that is typically made white by a kaolin—a clay mined at the top of the mountain, so to speak, so it is not tarnished by impurities (i.e. iron). The particles are very fine. Because of this it is less 'plastic' or workable. Porcelain was first used in the East—China/JApan/Korea.
When trade routes opened to the West, Europeans fetishized it: It was considered white gold. The Germans and the French competed to replicate porcelain. (Kings hired alchemists.) The first approximation was called white paste porcelain and was made by Meissen. (The German's won in 1710.) It is still manufactured today. Sevre (French) followed.
The Italians mimicked porcelain by taking their clay and covering it with and opaque white glaze using Tin Oxide as the opacifier. (But these earthenwares—iron rich, red clay fired to low temps—are more porous than porcelain.) Then they painted the imagery over the white background using oxides, cobalt, iron, and chrome. This is known as Majolica or Maiolica. I'm sure you've seen it. The earliest tin-glazed pottery was found to be made in Iraq in the 9th century. From there it spread to Egypt, Persia, and Spain before reaching Italy in the Renaissance.
Anyhow, there is a rich history on the material culture of porcelain. But it's a high end material. its more expensive and harder to work with. It's also very beautiful.
S T O N E W A R E S
High temp clays (2100–2300 degrees F) that have a variety of particle sizes in them making them much easier to work with. They tend to be buff, brown, or red depending on the materials. They are probably the most common clay bodies folks work with. They are cheaper and easier to use.
E A R T H E N W A R E S
Low temp clays, more common. Iron or talc makes them reach maturity at a lower temp (1800-1900 degrees F) than the stonewares. They end up more fragile and punky. Porous. Most Mexican pots and many Native American, African, and Indian pots are earthenware. It seems like warm climates get the iron rich clay. I don't know the science/geology behind that yet.
p l a t e s
P O R C E L A I N
18th Century, Korea
T I N W A R E
9th Century, Iraq
M A I O L I C A
17th Century, Italy
S T O N E W A R E
Wood fired Shigaraki-ware, 14th–15th Century, Japan
Shigaraki is an area in Japan where the clay source is thick with Feldspar. So, you'll see this rough texture from the feldspar chunks. It's super rough and varied. The surface comes from wood ash. The kilns were (and still are) fueled with wood and at peak temperature, the wood ash melts to form the drippy glaze. Different kinds of wood leave different colors—brown green, purple, pink, orange, black, grey. The amount of wood used also effects the surface quality and color.
German Beardman, salt fired stoneware, 17th–18th Century
Salt was introduced into the firing at peak temperature and formed its own glaze. Pots like this one are put into the kiln raw (no glaze) and the salt volatilizes in the heat and leaves a shiny, 'orange peel' surface. (Your North Carolina friends fire with wood as fuel and both wood and salt as the glaze component.)
Paul Cushman (1767-1833), Albany, New York
Salt fired stoneware jug
E A R T H E N W A R E
Fox Warrior Bottle (stirrup bottle), 7th–8th Century Moche, Peru
Skeletal Couple with Child (stirrup bottle), 3rd–7th Century, Moche, Peru
Terracotta Panathenaic prize amphora (jar), ca. 560–550 BC, Greece
Signed by Nikias as potter; attributed to Sikelos as painter
Terracotta amphora (jar), ca. 500 BC, Greece
Attributed to the Nikoxenos Painter
Maria Martinez (1887-1980), 20th Century, San Ildefonso Pueblo, New Mexico
Native American smokefired earthenware
Each one of these samples is rich enough to study for a lifetime. Thank goodness people do. Greek earthenware is absolutely mind blowing. Next time you're at the Met, go look closely at it. The technique and skill needed to make those kinds of pots is unbelievable. The quality of the painting and understanding of form is second to none. And quite of a few of those amphoras fit into the 'golden ratio' perfectly. It's astonishing, considering the time in which they were made. The impulse to make objects like that puts a lump in my throat. They are so loaded with information and we are so lucky to be able stand in front of them. The same could be said for Moche Stirrup pots from Peru. Look into those if you have time. Just amazing artistry. If I were gonna start over I would study art conservation and restoration so I could be around these objects.
Text written by Giselle Hicks. Check out her hand pinched wares in our store.