Cochise College           Student Papers in Geology

Geology Home Page                   physical geology  historical geology  planetary  gems           

Roger Weller, geology instructor

wellerr@cochise.edu

Ceramics
by Ryan Yearicks
Physical Geology
Fall 2009
              
  

The Wonderful World of Ceramics
Ceramics in Our World
 

            Ceramic materials are inorganic, nonmetallic materials.  Most ceramics are compounds of metallic and non metallic elements for which the inter-atomic bonds are either totally ionic or ionic but have some covalent character.  Some of these materials include: Aluminum and Oxygen (Alumina – Al2O3), Calcium and Oxygen (Calcia – CaO), and Silicon and Nitrogen (Silicon Nitride – Si3N4).  The term ceramic comes from the Greek word “Keramikos” which means burnt stuff, indicating that desirable properties of these materials are normally achieved through a high-temperature heat treatment process called firing.

 

 

            Ceramics have been around for many centuries.  Some of the earliest ceramic pots are believed to be from as far back as 24,000 BC in Czechoslovakia.  These were in the forms of balls, and human figurines.  These ceramics were made of animal bone and fat, mixed with bone ash, and a fine claylike material.  After mixing these materials were fired in kiln-like stoves at temperatures between 932° - 1,472° Fahrenheit. It is not know what these objects were used for.
 


 

            It is believed that the manufacture of glass was closely related to ceramics.  While firing the ceramics, if the clay contained a higher presence of Calcium Oxide (CaO) containing soda and then overheating the pottery kiln, it may have produced a type of glaze on the pottery.

The Ceramic Process

1.     Clay Preparation: This first step involves finding the right clay body for your work.  Most modern potters usually just buy their clay from manufactures.  The Native Americans and more traditional potters dig their clay from the earth, which gives them a feeling of being more with the earth and closer to their work.

2.     Wedging:  This is the process of missing the clay by pressing it into itself in a ball.  This process is also VERY important to get out all the air bubbles, which can cause the pieces to break during the firing process later.

3.     Forming:  After the clay is thoroughly wedged, it can then be formed using a variety of methods: Slab, Wheel, Coil, Pinch, Mold, or a combination thereof.

 

4.     Drying:  As the clay dries, it loses its water content, it becomes stiffer, and shrinkage begins.  As the piece is worked and put away at the end of the day, it should be wrapped in plastic to slow down the drying process and make it so when you come back your piece is still workable.

5.     Leatherhard:  After the clay has dried a few days, they will reach a stage call leatherhard.  This is the stage where the clay has lost most of its water through evaporation and loses some flexibility.  This is an excellent time to refine the final piece and add handles, and other decorative items.

6.     Greenware:  This is when the piece has lost all of its water through evaporation and has no flexibility.  The only thing you can do to it is break it.  This is a passive state where it’s just waiting on its first firing.

7.     Bisque Firing:  After the piece has dried completely and it’s ready to be fired, it’s loaded into a kiln and fired.  This firing is at approximately 1800 degrees Fahrenheit. This is usually a three day process.  Day one the kiln is loaded and the fire started but kept low to finish drying the pieces.  Day two the fire is turned up until the target temperature is reached the fire is turned off and the kiln is let cool down.  Day three the pieces are then removed from the kiln.

8.     Glazing:  The glaze is a mixture of ground glass, clays, coloring materials, and water.  It is applied by dipping, pouring, spraying, brushing, sponging, or any combination of these.

9.     Glaze Firing:  This firing is also a three day affair but the temperature is up to 2350 degrees Fahrenheit.

10.  Overglaze Firing:  This is an optional step.  This step involves a lower temperature (1300 degrees) and can include lusters, china paints, and decals.  This glaze goes over the higher temperature glaze, but the biggest disadvantage to this is that it is semi-permanent.

            The world of ceramics is a large part of our world and is involved in everything we touch and see today.  From our coffee cups to electrical components to ballistic armor used in the vest and helmets of our troops in the military to the heat tiles on the space shuttle, ceramics are in the world around us, and will continue to be far into the future.

 

 

100_1751.JPG100_1757.JPG100_1750.JPG

These pictures are of chess pieces made from a hard ceramic. 
They were made in South Korea probably in the late 1980’s or early 1990’s. 
From left to right: queen, queen and king, king.

 

 

 

The following is a list of ceramic products and examples of their uses:
 

INDUSTRY SEGMENT

COMMON EXAMPLES

Structural Clay Products

Brick, sewer pipe, roofing tile, Terracotta, clay floor and wall tile, flue linings

Whitewares

Dinnerware, floor and wall tile, sanitary ware, electrical porcelain, decorative ceramics

Refractories

Brick and monolithic products are used in iron and steel, non-ferrous metals, glass, cements, ceramics, energy conversion, petroleum, and chemicals industries

Glasses

Flat glass (windows), container glass (bottles), pressed and blown glass (dinnerware), glass fibers (home insulation), and advanced/specialty glass (optical fibers)

Abrasives

Natural (garnet, diamond, etc.) and synthetic (silicon carbide, diamond, fused alumina, etc.) abrasives are used for grinding, cutting, polishing, lapping, or pressure blasting of materials

Cements

Used to produce concrete roads, bridges, buildings, dams, and the like

Advanced Ceramics

 

1.     Structural

Wear parts, bioceramics, cutting tools, and engine components

2.     Electrical

Capacitors, insulators, substrates, integrated circuit packages, piezoelectrics, magnets and superconductors

3.     Coatings

Engine components, cutting tools, and industrial wear parts

4.     Chemical and Environmental

Filters, membranes, catalysts, and catalyst supports

 

 

Materials Science and Engineering: An Introduction, William D. Callister, Jr., John Wiley & Sons,      Inc., New York

http://ceramics.org/

http://seco.glendale.edu/ceramics/ceramicprocess.html

The use of the following document is hereby given written permission by the author for use by Roger Weller, Instructor of Geology at Cochise College, for any way he intends to use said document, to include his geology website, and any other way he designates.