Mrs. Hasselbeck
Ceramics I
Fall Semester 2014-15
Homework #1: Overview of Clay
___ / 25 POINTS
CLAY FORMATION AND PREPARATION:
Clay is one of the most plentiful materials on earth. About 75 percent of the earth’s surface is either clay or can become clay. Clay is
formed from a granite-type rock called feldspar. Clay is formed through a natural process known as geologic weathering. This weathering
process breaks down the feldspar through either the physical action of abrasion due to wind or water, or a chemical action of acids which
break down the rock. The process of weathering is a bit more than just the crushing or decaying of rocks. The rock is not only crushed but
also mixed with other elements or minerals… and these are the things that give clays their distinguishing characteristics. Say for instance,
iron is the ingredient which makes many clays red in color. Iron is also one ingredient which can make a clay lowfire, as it lowers the melting
point.
Although nearly every land mass or island contains numerous clay beds, most of these sources need to be modified to make the clay
useable. High iron content, alkaline impurities, or too much foreign matter limit the use of much clay and require extensive preparation
before use. Over 100 million tons of clay are mined in the United States each year!
CLAY MANUFACTURING | INDUSTRY | HISTORY:
Clay is the most significant of all the ceramic materials. That may seem obvious, but glass, plaster, and cement are also some important
ceramic materials. By definition, ceramic materials are high-temperature, inorganic(cannot grow), nonmetallic (not metal), and crystalline
(forms a crystal structure).
Although we are creating pottery and sculpture from clay in this class, most clay is used in the production or manufacture of industrial
products such as:



plumbing fixtures, (toilets, sinks, etc.)
roofing and drainage tiles
refractory items (refractory means resistant to heat or melting)
o such as firebricks, (used in fireplaces/kilns)
o spark plugs (used in engines),
o electrical insulators (used in electronics)
o space age uses like space shuttle tiles, rocket parts, etc…
The type of pottery/artwork we will be doing in this class is the same done by studio potters. The essence of studio pottery is creating things
out of clay by hand - as individuals… whether the items are functional (meaning you can use them) ware (pots or pottery) or purely
decorative (to look at) ware – this is a tradition that has been carried on for centuries. It is believed that many, many centuries ago clay was
first used in primitive cultures, creating primitive forms- such as deities (god-figurines) made for religious or ritual uses - or rudimentary
(rustic/basic) vessels (containers) used to store or serve food.
STRUCTURE OF CLAY AND CHEMICAL WATER:
Clay is a compound of elements minerals with this basic formula: Al2O3•2SiO2•2H2O. This is the chemist’s way of saying that clay is
one part alumina (Al2O3), two parts silica (SiO2), and two parts water (H2O). Alumina and silica are oxides - each is a combination of
oxygen and one other element, aluminum (Al) and silicon (Si). The water in the formula is called chemical water.
Clay can be wet (with the water of plasticity) and dry out over and over again- and it will still have its chemical water. Chemical water
remains a part of the clay until the chemical change of firing occurs- then the chemical water is gone. This chemical changes happens
when it reaches about 1000° F. Once clay has reached this temperature in the kiln it the chemical water is gone and it cannot be recycled.
If you were to place fired clay in water, it would never soften again.
The process of attaching the water molecules to the aluminum and silicon is called hydration. It’s the most important difference between
clay and ordinary dirt. Sand and “dirt” do not have chemical water found in clay.
Mrs. Hasselbeck | CERAMICS II | HOMEWORK #1
NAME:
BELL:
DATE:
Check your reading! Supply the missing word(s) to complete the statements below.
1. This is the type of rock from which clay is formed: ______________________________________
2. The natural clay formation process is called: ________________________________________
3. During the formation of clay this common element can often be mixed in – resulting in a reddish color clay:
___________________________________
4. How are the impurities or foreign matter removed from slaked down clay? ____________________
5. After manufactured clay is mixed, how are air bubbles removed? __________________________
6. Approximately how many tons of clay are mined the U.S. each year? ________________________
7. Long ago, when potters would establish their potteries near water sources that uncovered clay, what would they
use for firing of their kilns? ______________________________________________
8. Besides clay, what are three other important ceramic materials? _______________________,
_______________________, and _______________________.
9. Most clay is used in the production or manufacture of: __________________________________
10. What does refractory mean? Resistance to… ________________________________________
11. How would you define a functional ceramic item? _____________________________________
12. How would you define a decorative ceramic item? ____________________________________
13. What is believed to have been the first known fired items found which were made for religious or ritual uses?
___________________________________________________________________
14. What does the word “ware” mean in Ceramics? ______________________________________
15. The basic formula for clay is ____________________________ (Al2O3) plus
____________________________ (2SiO2) plus ____________________________ (2H2O)
16. There are TWO types of water in a bag of ready to use clay… the wet water which makes the clay slippery and
sticky is called the water of ___________________________. What do we call the dry type of water in the
formula for clay? ___________________________ water
17. When does the chemical water leave clay? _________________________________________
18. Clay can be recycled over and over until what happens? ________________________________
19. What is the scientific name for attaching the water molecules to the aluminum and silica molecules?
___________________________________