Some basic pottery information and definitions

Pit firing

At some remote period in time (c.8000 b.c...) man discovered that clay, when baked in a fire, would become hard and durable. For thousands of years pottery was fired in a shallow pit on a bed of twigs. Broken shards covered the heated pottery to provide protection from the fuel and to retain the heat. With a continual application of dry twigs and grass a red heat could be achieved, after which the coals were covered with soil and allowed to cool. Smothered with ash, the red clay body was usually black from carbon. Burnished and incised surfaces were the only decoration possible. All early black ware was fired in this manner, as is the pottery of some aboriginal tribes throughout the world and dozens of ceramics artists throughout Canada.     As man evolved, easier to clean clay storage containers replaced ineficient leather sacks and goat stomacks . Wine, milk and cheese, breads, yeast and spices, were stored for longer periods of time than previously posible. Many types of clay were used, many types of firing and many diferent types of kilns were constructed.     The chinese were the first, and for many years the only country to produce higher quality, higher fired ware. The chinese perfected firing and kiln construction more quickly than there European counterparts, and organized potteries full of people "factories". After centuries of trade with Europeans, the Chinese began to high fire a white clay material called "Puteunse". Highly valued, it was a hugely traded commodity. In the 1800,s it was finally copied by Europeans with blends of kaolin's and feldspars.
    Trade of pottery for the last couple of centuries was as common as food and clothing since most food came in clay containers or wooden barrels, and slowed only during the middle of the last century with the invention of plastics.
    Today, potters in North America have led a revolutoion of art pottery, driven by creativity and inovation instead of function. Industry also has continued to evolve. Heat resistant tiles have helped NASA to send Astronaults to space and Ceramic engines are a reality in the near future. High refractorie materials spun into wool-like materials provide superior heat retention and heat resistant properties enequaled with any other materials. Clays are abundant material, Most of the earth consists of large quantities of clays and feldspars.
 

Definitions

Reduce or reduction: Reduction of pottery is done always while the pottery is very hot! In the case of raku, hot pieces are taken out of the hot kiln and place in a combustible material, such as sawdust. The piece and the sawdust are covered so as not to flame. The combustible material and heat together search for oxygen, (the third element which is needed for combustion). In many cases, materials such as copper oxide, (normally green) while in the molten stage will give up an atom of oxygen freely, thus reducing the copper oxide and changing it on a chemical level to cuprous oxide which is red. Copper roofs also go through a chemical change over time. The opposite of reduction is oxidation.

Fire or fired:  The baking of the pottery in an oven for pottery known as a"kiln".

Maturity: The clay is fired to the temperature necessary to make the clay as strong as possible

Clay: the 3 types

Earthenware is a clay defined mainly by the temperature needed to "FIRE" to maturity. By Clay standards this is a low fire clay. Earthenware clay can be of any color.
 

Stoneware: is a clay defined mainly by the temperature needed to "FIRE" to maturity. Stoneware clay can be of any color. Normally this type of clay is the most generally resilient of the three types of clay and most suitable for everyday kitchen tableware. By Clay standards this is a medium fire clay. aproximtely 2200 degrees F.

Porcelain: is more easy to define but more often defined wrongly. I believe in the early chinese "true" porcelain definition, made of a material called "Putunse" and later copied by Europeans with a blend of kaolin's and feldspars, is a clay defined Partially by the temperature needed to "FIRE" to maturity, But more importantly needing to be white and translucent and very hard. True porcelain has a ringing tone when struck, which is hard to replicate with its lower fired and softer copy. By Clay standards this is a high fire clay. While porcelain can be of lower firing, it is generally accepted that fine porcelain is fired to temperatures above 2350 degrees Fahrenheit.

Kaolin:

Egyptian paste: utilized soluble soda salt compounds which rise to the surface during drying and when heated sufficiently became the  first "glazed" objects.
First used before 5000 b.c. Rhodes, Daniel. Clay and Glazes ( 1975)
 
 

Feldspar:

Peteunse:
A dense
 

Email me at   Ronald@lepotier.com