Tuesday, December 7, 2010

The Science Of Ceramics - Chapter One. Great Ball of Fire


I am second generation in a ceramic art and design businesses, which many of you may know, goes by the names of Andersen Studio and Andersen Design, our production and wholesale S corporation.

I learned ceramics from my father, Weston Neil Andersen, who learned techniques of  production ceramics from Eva Zeisel as part of the industrial design course he was enrolled in at Pratt Institute. It was a landmark course teaching ceramics as a slip-casting process rather than the wheel thrown technique still today commonly associated with the making of ceramics. The purpose of the course was to educate the designer about industry production processes. The primary source of my father’s knowledge of the molecular processes of ceramics are the books that have long been in our bookcases. From these books, my father taught himself how to design the original glazes that are a signature of Andersen Studio Stoneware.

I grew up in an environment in which the ceramic workshop and retail showroom were inseparably connected to the home, somewhat like the chicken farm in which my father was raised. The process of ceramics was both the background and foreground of our family life. Whenever we had a problem to solve in one of the slips or glazes that we make from raw materials, dad would always talk about the crystal interactions, the suspension of the molecules, what happens during the heating process, viscosity, deflocculating, and other scientific terms and concepts. These were processes, which are taking place at a scale that is not visible to the unaided human eye.

Later I became interested in processes taking place at an even smaller molecular scale, that scale which physicists refer to as the quantum level of accuracy, where in nature follows radically different laws than those that govern within the scale of “the classical limit”. Contemporary science of ceramics has evolved within the classical limit, but in its very beginnings ceramics was an intuitive process. The atomic theory of on the nature did not enter the scientific mainstream until the early 19th century. Perhaps at a future date, ceramic understanding will incorporate the mysterious events taking place with in the quantum domain. Currently, about a century after the discovery of Planck’s constant, there still exists a gulf between scientific worldviews based in the description of nature within the classical domain and that at the quantum scale. I expect to be primarily focused within the classical limit in this discussion.

Ceramics involves molecular interactions that occur during the heating and cooling of matter. Whether one believes that the earth began as a cloud of white hot gases spun off from a Sun, or an accumulation of dust particles that became heated through the constant addition of new layers, it is generally accepted that at one time the earth was very hot. The raw materials used in ceramics came into being during the cooling down process of the white-hot earth.

The earth has a radius of 4000 miles but most of the minerals that man uses are within the first ten or so miles that make up the crust. The original crust consisted mainly of basalt, a very hard rock with a glassy crystalline structure, testifing that at one time it cooled very quickly. Basalt is made up of fluxes (calcium oxide, lime and magnesium oxide), alumina, and silica.

Likely, even before the earth’s cooling process was complete, the crust was affected by physical and chemical forces. The cooling process must have produced clouds of gases, which condensed into water and acids. The grinding and pounding of the water loosened particles of rock, which then became abrasives, which further attacked the earth’s outer balsam crust.

The process produced a fine sediment, which was more vulnerable to chemical reactions than the balsam crust. The result was the introduction of separate minerals. Calcium oxide (lime) was leached out by acid solutions and turned into calcium carbonate (lime stone). Silica and alumina floated freely about or combined with water to form clay. The newly formed minerals had different weights, which the currents of water picked up, sorted according to weight, and then deposited, in different locations around the globe.

 Layers of different sediments formed at different locations on the earth. The weight of the layers created pressure on underlying layers causing further changes. Clays became rocks; silica and quartz became sandstone and limestone metamorphasized into marble.

As the earth continued to cool, it shrank and the hard rock crust became wrinkled and cracked. The sedimentary layers fell into the cracks and valleys and became thicker, harder and more complex deposits.

Volcanoes of inconceivable magnitude erupted. A sea of Granite poured out and filled the spaces between the basalt and layers of sediment. The basalt slowed the cooling process of the granite creating larger and less glassy crystals. Huge pieces of granite floated on the surface of the basalt and lifted continents of sediment above the water level. The continents shifted and bumped into one another causing great masses to pile up which today are known as the Alps and the Himalayas.

As the granite was exposed to the physical and chemical forces it was redistributed in huge quantities around the earth. The mystery of life emerged from primitive cells and found nourishment in the sediment and the atmosphere only to be buried under layers of new rocks to become fossils.

And so on and on goes the creative process of nature.

Silica and alumina are one of the most common substances on earth. Silica constitutes approximately 60% of the earth’s weight and alumina constitutes another 18%. Fourteen elements constitute 99.224% of the bulk of earths crust, of these 11 are used in pottery, composing 99.169% of the earth crust. All of the basic raw materials used in ceramics are found in the United States (and other parts of the world). These raw materials are China Clay, Felspar, Nepheline Syenite, Alkai salts, Nitrates, Borates, Lead and Zinc.

More about these materials in my next post.

For those interested in reading directly from one of my sources of inspiration for this post, I recommend Pottery Glazes by David Green

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Monday, November 29, 2010

The History of Ceramics - Chapter One

Ancient Indian Coiled Pottery Pot 
from The Mid-Western United States
Photo courtesy of Barnhill Indian Trader

The beginnings of human history are cloaked in mystery, but as speculation goes, Ceramics emerged around 8000 BC during the Neolithic Revolution when man first started using tools and developing agricultural skills. This produced a need for vessels to carry and cook the produce.

There is one exception that calls for mentioning, Dolni Vestonice in the Czech Republic, where models of animals and a Venus figurine have been dated to about 25,000 years ago

The first vessels were baskets. The ubiquity of early coiled ceramic forms, from the Middle East to China to the America’s, suggests that pottery was first discovered when baskets were coated with clay so that they could hold small seeds and grain. Then one day the basket fell into the fire and it was discovered that heating hardens the clay making it more suitable as an airtight vessel. This event occurred synchronistically in different parts of the globe

Around 5000 BC it was discovered that by burnishing the half dry clay with a stone or a bone a smooth and more airtight surface could be created.

Ash firing was discovered when a pot was placed upside down on hot coals, reducing the surface of the rim to a glossy black. The upside down vase was also the first kiln. Then came the hole in the ground above which a bonfire was lit. Later the hole in the ground became a cave in a hill. The Chinese and Japanese expanded this into a complex system of successive chambers climbing over the slope of the hill

The kilns designed by the ancients are still in use today but have undergone modifications due to changes in fuel, materials, and the need for larger scale production. The greatest revolution in the technology of the kiln came with the discovery of electricity. The electric kiln simplified the process of firing as well as making it safer. This increased the popularity of the art of making the ceramics.

At first all pottery was made by women as part of the household chores, but as civilization developed, the “market” made its appearance and pottery became the work of the skilled craftsman. Around 3000 B.C, a simple revolving wheel existed in Mesopotamia, the area between the Tigris and the Euphrates Rivers The potter’s wheel economized the production of ceramics. By 4000 BC pottery making was predominantly masculine and the use of the potter’s wheel was commonplace.

The origins of mold making are traced back to Hellenistic Greece and the Roman Empire. This was a clay bowl with a design pressed into the inside. It was fired and then clay was hand pressed into the inside. A potter’s wheel was used to spin the surface until it was smooth. As it dried the clay reduced in size so that the “green” clay form was easily removed from the fired clay form.

Plaster, needed for molds used in ceramic slip casting dates 9000 years. The Romans cast in plaster to make copies of Greek sculptures and so it is much to my surprise to learn that the development of slip casting is credited to Ralph Daniel of Coolidge, Great Briton at the late date of 1743. I’ll be looking into this and reporting what I learn in future posts.

During the process of researching this series I have been using both the Internet and my father’s old ceramics books, some of them dating to the days
in the 1940’s when Dad studied ceramic slip casting in the Industrial Design department at Pratt Institute . His instructor was none other than the illustrious Eva Zeisel. Eva was quite taken aback when dad told her that he was actually going to move to Maine and start a hands-on ceramic slip casting studio of his own. This is what brings the organic quality to my parent’s designs, distinguishing their work from their more famous mid-century contemporaries who primarily designed for large production companies.

I love the process of a small slip-casting studio and I have also been enjoying researching and writing about the History of Ceramics. I look forward to continuing this discussion of The History of Ceramics and will continue it on this blog, Talking About Ceramics.  

I hope you enjoyed reading this at least half as much as I am enjoying writing it.   

The next email in this introductory series will be The Science of Ceramics. I can’t wait to dig into more of my father’s old books.

You can sign up to receive this email series and other news of interest on Andersen Studio's Home Page. 

One of my favorite references for this article has been Ceramics- A Potters Handbook by Glenn C Nelson, 1971 

Check out Biblio Books for great prices.