Jan 02 2009
Things you might want to know
Ceramic Terms
1. CERAMICS: clay or the art of working with clay
2. CLAY: small chips of rock mixed with water
How is clay different from ordinary mud?
A. When clay is wet, it can be molded or shaped without breaking
B: When clay is fired, it is rocklike.
3. WEDGING kneading the clay, we wedge the clay to remove the air bubbles, and to mix it all together so that there is same amount of moisture throughout the clay.
4. FIRING: heating the clay until most of the moisture is out of it.
5. KILN: an oven or furnace in which the clay is fired, the bisque or first firing is at 1800 degrees, the second if it is High fire, is at 2350 degrees.
6. SHRINKAGE: contraction of clay during the drying and firing. Because clay shrinks as the moisture goes out of it, it is important that a ceramic piece is completely finished before letting it dry. If a wet handle is put on a somewhat dry cylinder, the handle will shrink more than the cylinder and will later
fall when it dries and shrinks. This applies to anything that is made of several pieces, Also for a mug or cup handle, remember to make you handle big enough so that you can still get your hand in it after it has shrunk. We user two methods to attach one piece of clay to another piece of clay.
7. First SCORING, which is scratching fine lines into the; wet clay to roughen up the surface. We can also add SLIP that is thick liquid clay that can be added to the rough surface to help the pieces to stick together better. A clay piece is call different things depending on how dry it.
8. LEATHERHARD: condition of clay when it is starting to dry. It is softest enough to be carved, but it is about as stiff as shoe leather. It is too stiff to bend. Clay in this state can be handled without misshaping it, for this reason, we wait until clay is leatherhard before assembling a box, or a rectangle base so that the sides will remain straight.
9. GREENWARE: A dry clay piece that is ready to be put in the kiln for the first time (bisque fire). Clay, while drying is very clod and clammy. This way you can tell that the clay is dry enough to put in the kiln not by looking at it, but feeling if it has come to room temperature. When it has reached roo
m temperature, it is ready to be fired.
10. BISQUE: unglazed clay that has been fired once, it is very dry We wash bisque pieces briefly before glazing them, to clean off the grease left from fingers, to get the dust off, and so that they
will absorb the glaze better.
11. BISQUE FIRING the first firing to about 1800 degrees, in this firing, we do it slowly so that the moisture will evaporate slowly. The purpose of this firing is to dry the clay completely, to make the clay stronger, to see if it has air bubbles or cracks. There are 2 reasons why clay blows up in the kiln: Air bubbles, and the clay is not dry enough. We fire our clay pieces twice
12. GLAZE firing, the second firing can be at either 1800 degrees (low fire), or 2350
degrees (high fire). The purpose of the glaze firing is to melt the glaze to its maturation point and to decorate the ware.
13. GLAZE is a special liquid glass, and we use it for decoration and to make our ware waterproof.
14. UNDERGLAZES: these are not glazes. They are not made with glass. They are a special kind of watercolor paint made especially for clay. We use underglazes when we want to use many colors or find designs that we to not run together in the kiln. We put a clear transparent gloss glaze over our underglaze before putting into the kiln.
15. GLAZING PROCESS: put wax resist on the bottom of your pot t
o make it easier to clean off any spilled glaze. Always glaze the inside of your pot first. Use just one heavy coat. Never glaze the bottom of your project, when glaze melts, it becomes sticky and gooey, at this point, the glaze will glue your project to the shelf. It will have to be broken to remove it from the shelf.
