Ceramics
Clay and Pottery – An ancient art
Since the first piece of clay fell into a fire and was transformed into a glasslike material, people have used clay for domestic wares, ritual tokens, and decorative items. The oldest known pottery fragments stem from the Hittite civilization, 1400-1200 B.C.
Where Clay Comes From
Clay comes from the ground, usually in areas where streams or rivers once flowed. It is made from minerals, plant life, and animals—all the ingredients of soil. Over time, water pressure breaks up the remains of flora, fauna, and minerals, pulverizing them into fine particles. Larger particles are filtered out through rocks and sand, leaving silt to settle into beds of clay.
Pottery is the CERAMIC ACT of making pottery items. It is the term used to describe the art or craft of a Potter or the manufacture of Pottery.
- Greenware refers to unfired objects. – at this stage clay is in its most plastic form, soft and malleable.
- Leather-hard refers to a clay body that has been dried partially. At this stage the clay object has approximately 15% moisture content. Clay bodies at this stage are very firm and only slightly pliable.
- Bone-dry refers to clay bodies when they reach a moisture content at or near 0%. It is now ready to be bisque fired.
- Bisque Firing- occurs when the object is shaped to the desired form and fired in the kiln for the first time, known as “bisque fired” or “biscuit fired”. This firing changes the clay body. Firing produces irreversible changes in the clay. It is after firing that the article or material is called POTTERY.
- The chemical changes after bisque firing also change the colour of the clay.
- Glaze fired is the final stage of some pottery making. A glaze may be applied to the bisque form and the object can be decorated in several ways.
- Glaze – is a liquid GLASSY coating on pottery. The primary purposes of glaze are decoration and protection. One important use of glaze is to make porous pottery vessels IMPERMEABLE (water proof) able to hold water and other liquids. Once the glaze is applied the object is “glazed fired”, which causes the glaze – glass like material to melt, then adhere to the object. This is what makes it ‘IMPERMEABLE’-waterproof.
There are three main clay types – Earthenware, Stoneware and Porcelain
There are three main Hand building techniques – Pinch Pots, Coiling and Slab construction
HAND BUILDING is working with clay by hand using only simple tools, not the pottery wheel. Before potters had the wheel, they were creating beautiful pots and clay forms using clay, their hands and fingers, and basic hand tools.
Some common techniques
Joining techniques
- Scoring /scratching,- Making rough scratch like marks on edges of clay to be joined.
- Transferring clay,
- Slip/Slurry- Clay diluted with water used to join pieces of leather hard clay. Should have a whipped cream consistency
Sgraffito – Scratching designs on to the surface of pottery.
Vitrify– High heat used to harden clay and remove all water.
Kiln – A furnace that reaches high temperatures (more than 2 X higher than a domestic oven) for firing/glazing clay.
Construction Techniques – Video Overview
Pinch Pot Method video
Begin a pinch pot by forming a lump of clay into a smooth sphere that fits the size of the hand. This method is similar to the way the Native Americans shaped clay into useful pots. While holding the sphere of clay, press the thumb into the centre of the ball, half-way to the bottom. While revolving the ball in one hand, press the walls out evenly with the thumb into the inside and the fingers on the outside. Smooth the surface with a damp sponge.
Coil Method video
Coils of clay can be used to build bowls, vases and other forms in various shapes and sizes.
Slab Method video
Ceramic Tools
