Ceramics
Types of Firing
Types of Firing: Oxidation, Reduction, Salt, Wood, Raku
Oxidation firing is typically done in an electric kiln, but can also be done in a gas kiln. Oxygen is free to interact with the glazes when firing. Oxidation firing allow very bright, rich colours. High temperatures may be used, or low temperatures.
Reduction firing is typically done in a gas or other fuel burning kiln, since the corrosive effects wear out the elements on an electric kiln. In reduction firing, oxygen is prevented from interacting with the glazes during glaze maturation. This is done by adjusting the fuel in a gas kiln, or by adding organic material such as in Raku. As the organic material burns it uses up oxygen, leaving an oxygen-less environment. Reduction firing typically is used to obtain mottled, rich, earthy colours, often the iron from the clay shows through and gives a speckled look. Typically high temperatures are used in reduction firings.
In Salt firing, and Sodium firing, salt or sodium are introduced during the final stages of firing. The atmosphere allows pieces to get a glazed like finish without glazes. Sometimes it takes on the appearance of orange peel. Interiors of pots should be glazed since the salt atmosphere often won't reach deep into them.
Wood firing uses wood as fuel instead of gas or propane. In pit firing, a large hole is dug in the ground, wood and pots placed in, wood started on fire, and the whole thing covered with dirt to smolder. Pots are then dug out.
Raku is a technique where a pot is heated until glowing, then pulled with tongs from the kiln and placed into a reduced atmosphere, such as a metal can full of pine needles, newspaper or leaves. After cooling somewhat, the piece is often plunged into cold water, creating crackle effects. In Raku, unglazed areas of clay become black due to the carbon from the burning fuel. When carbon is scrubbed off the glazed areas they are often bright metallics such as copper and bronze.
Activ-Clay
Activ-Clay is an air-drying artist quality clay that is easy to manage, comes in 6 gorgeous colours, and is a blast to work with! You can free-hand model right out of the bag. Make coil snakes and roll out slabs for building boxes, pots, containers, figures, jewellery, and anything else your imagination will drum up. Here are some basic technique ideas to get you started...
Pinching Out Shapes
If you want to make small pots, bowls and animals, this technique will help you start out right! Make a ball of clay and press your thumb into the clay to make a hole. Gently squeeze the clay between your thumb and fingers working evenly around the ball of clay to open up the shape. Stop from time to time to see how your shape is progressing. Leave the pot at least ¼-inch thick for strength.
Rolling Coils
Here's another great technique for building pots, boxes, or decorative bowls. The coils are made by rolling out clay coils, or thick spaghetti snakes with your hands. For small pots, the coils should be at least ¼-inch thick. To ensure a good, strong container, the rule of thumb is: 'The larger the pot, the thicker the coils'.
Making Slabs
Flat slabs of clay can be used for tiles or for building boxes and containers. You will need a rolling pin and two pieces of wood - paint stirrers, lattice, or rulers work great. Place a ball of clay between the lengths of wood; flatten the ball with the rolling pin. The thickness of the wood controls the thickness of the slab. You can use cookie cutters, paper patterns and a knife to create clay shapes. Use rubber stamps or anything with a pattern or texture to make exciting designs in the clay.
Joining and Attaching Activ-Clay Pieces
When joining clay pieces, the clay should be scored or roughed up, and moistened with water before pressing the pieces together. If you allow the clay to harden slightly it will be easier to handle without loosing its shape. You can use an adhesive to add things to your model or pot after it dries.
Extruding
Press clay through a garlic press or a clay extruder to create uniform shapes for your masterpiece! Use the extruded clay as hair or fur and decorate your creation.
Painting and Finishing
You can paint Activ-Clay with many different mediums. Acrylic paint works great. If you choose water-colours or poster paints, you will need to seal the piece with an acrylic sealer. Colour can be applied with a brush or sponge, depending on the effect you want to obtain. Why not try spattering the colour with an old paint brush?
The sky's the limit to your creativity. Let your imagination go wild!
Ceramics - Slip Trailing
Slip Trailing is an alternative, safer way for producing low relief designs. Take some slip in a jar or small container and add a dash of plaster (or any thickener). When the slip becomes thicker, fill a slip trailer bottle and use it to apply your low relief design on the piece.
Ceramics - Greenware Care
It is best to trim cast greenware before it dries hard. Use a fettling knife and cut off the excess trim and seam line. Then with a soft, wet sponge wipe smooth. When you have to trim dry greenware, first spray the area that needs trimming with water. Do not soak it. Spray it lightly and let the water be absorbed into the clay. When the clay is wet enough cut away the trimmings and smooth out with a wet sponge. If working extensively on engraving a low relief design, try to keep it wet as long as your work is in progress by spraying it with water every so often or keeping it covered with a plastic bag during work breaks.
Ceramics - Aging of clay
Aging is a very important step in improving workability and plasticity of clay bodies because it takes time for water to penetrate between the clay particles and produce a good and permanent bond. Bacterial growth also has a definite effect on improving plasticity of the clay. It is suggested that some old clay should be left in the container where new clay is added to accelerate bacterial growth in the clay. The great Chinese potters have for centuries aged their clay in underground pits. It is said that potters would mix clay bodies for their children to use while they would use clay aged for them by their fathers.