Clays

Student Objectives: Students will learn about the six types of clay and be able to identify some of their uses.

Tips for the Teachers: Bring as many examples as possible of products made from the six different types of clay and discuss them.

Suggested Activities:

1. Have students make clay models or pottery.

2. Demonstrate the absorbent quality of kitty litter in class.

3. Have students paint pictures on light colored tiles. These may be used as gifts for decoration or hot pads. Be sure to use enamel paint, and give students specific instructions for safety.

4. To demonstrate bentonite clays, use compressed sponges. Have students observe what happens when water is added. Discuss “expandable” and “non-expandable.”

Measurements/Evaluation:

1. What color can natural clay be?

2. How many different types of clay are there?

3. Define “expandable” and give and example.

4. When clay is baked in a kiln, it becomes very hard. Can it be softened with water after this?

5. List six examples of how clay is used.

Clays

Clay is a soft mineral that bends easily. It is found in most soil and many types of rock. Clay is an important part of soil. It soaks up fertilizers and other things that plants need and holds them where the roots can get them. The United States has all types of clay, and more of each than any other country. Almost all of the states mine clay.

Clay can be brown, red or gray, depending on what minerals are in it. There are six different kinds of clay, and each can be used in special ways.

Kaolin is the most valuable type. The ancient Chinese people used it to make the fragile dishes and tableware that we call china and still made today. Kaolin is also important as a coating for paper. The slick coating on magazine pages is an example of this.

Ball clay is good for pottery and sculpting. Fire clay is made into strong, heavy products like brick and sewer pipes.

Fuller’s earth soaks up grease and liquids well, so is used for cleaning grease from cloth and for absorbent products like Kitty Litter.

Bentonite is divided into two groups, expandable and non-expandable. The expandable types swell to 15 times its dry volume when wetted and can become liquid. They are used in chemical compounds and as plugs in the walls of oil and water wells. Non-expandable bentonite, like other clays, become soft when wet but not liquid and do not swell. These clays can be baked in a very hot kiln to harden them and remove the water. After this has been done, they cannot be softened with water.  Bricks and pottery are two examples of these products.

Common clay is used in cement, pottery, bricks and tiles. There are also uses for the different clays in rubber, paint and medicines.

Directions: Finish the clay pots.