CLAY

Beyond all of the techniques that class assignments will teach you, your biggest task in this course will be to get to know clay. One of the hardest things about learning to do ceramic work is learning to keep your clay in the right state for the job you are doing. If you are trying to do something, and meeting with failure, try making your clay harder or softer (wetter or dryer), or try to come up with an easier way to make the object. Once you really understand clay, it will be second nature for you.

THE STATES OF CLAY IN THE CERAMICS STUDIO

  1. Dry: " air floated", processed clay powder. There are many types and brands of dry clay materials available on the market. They vary in fired color, wetted consistency, firing limits, and texture, and can be combined in thousands of ways to produce clay bodies which are especially good for different purposes.
  2. The 'S's: Slurry- Slurry is any material suspended in water.
  3. Slip- Slip is clay with enough water added to make it brush-able
  4. Slake- To slake is to place in water so that lumps break down and wet into slurry.
  5. Slop- Slop is scrap clay that has been slaked in water.
  6. Slouch- Someone who doesn't learn the vocabulary on this sheet.
  7. Wet or Moist Clay : plastic . plastic clay is the stage when the material is dough-like, it can be modeled, bent and squeezed.
  8. Leather Hard:: the clay is still fairly malleable and can be carved, burnished, paddled, brushed with slip, etc. Some slab work is joined at the leather hard stage. This is the stage when most potters trim feet, add attachments, and/or clean up their pots for firing.
  9. Bone Dry: Clay work which is as dry as it can be without removing the chemical water, which occurs in firing. Bone Dry Clay is nearly impossible to alter other than by subtractive techniques. The color of the clay will appear to lighten, and the clay is at its most fragile stage. Be extremely careful when handling your own bone dry pots, and avoid handling other student's work unless you are helping to load a kiln. Always remember that you depend on others to treat your work with respect and give them the same consideration. Never pick up a bone dry pot by its handle.
    Clay can still be recycled at this stage- don't waste clay, use the slop barrels. Reclaimed clay from slop is especially plastic- great for handles or difficult-to- throw forms. You can use plaster bats to dry slop to a workable consistency, and many potters who don't have clay mixers mix all of their clay this way.
  10. Greenware refers to clay before it is fired. Usually it refers to leather hard or bone dry ware, but as a category it occasionally refers to wetter states of clay.
  11. Bisque: clay is bisqued in the first firing. The physical water is evaporated from clay as it becomes bone dry; the chemical water is removed in bisqueing. Stoneware clay will be pinkish in color after the bisque. Bisqueing changes the clay, making it harder but still porous enough to accept glaze. The clay can no longer be slaked. Bisqued pots can hold water, although it will seep slowly through the pores in the clay. The clay is much stronger at this stage, but still not strong enough to be picked up by the handle, especially if it is full of glaze You may get away with this nine times out of ten, but the tenth time it will be your favorite piece you lose- Murphy's Law of Ceramics. Handle bisqued pieces as little as possible, and always wash your hands first. Oils from your skin can make the glaze adhere poorly, causing it to pull away from the clay in patches in a curdled looking surface. This is called crawling. Dusty pots are also prone to glaze crawling problems; rinse your pots and allow them to dry before glazing.
    It's a good idea to cover bisque with clean plastic if you MUST wait a long time before glazing, but the best way to avoid crawling and learn the most about glazing in the least time is to glaze your pots as soon as possible. The more often you have glaze fired pots to look at, the faster you will be seeing better results.
  12. Glaze fired ware:: Fired twice, the second time with a coating of glaze. Ideally, glazed ware should be fired to a high enough temperature to make it vitreous. When clay is vitreous, it is no longer porous. If you fired it much hotter, the clay would melt. Vitreous clay is also referred to as being mature. Punky refers to clay that is not fired to maturity. When you thunk punky ware it goes "punk" not "ping".

WORDS TO THE WISE

CLAY SHRINKS AS IT DRIES! If your pot is stuck to the bat or the board, or the table, and is allowed to dry that way, it may split across the bottom as it tries to shrink. (It tears itself apart.) Remember to come back and release wet clay objects from the surface they are sitting on once they are stiff enough. Large or very broad flat pieces should be placed on newspaper and a layer of sand while they dry, so that they can move as they shrink.

DON'T TRY TO JOIN TWO PIECES OF CLAY THAT ARE AT VERY DIFFERENT STAGES OF WETNESS. This is very much related to the idea that clay shrinks as it dries. If you add clay that is very wet to clay that is leather hard or drier, the wet clay will have much more shrinking to do and cracking will result. A very wet handle attached to a too-stiff pot will be very likely to fall off completely. Here are a couple of hints to make working with attachments easier:

- In handbuilt pieces where you are building up from the bottom, you will have to let the base stiffen up somewhat so that it can support the weight of added layers. However, don't let it get too dry, and wrap the top of the bottom section so that it will stay moist enough for attachments.

-If you must add softer parts to harder ones, it is sometimes possible to form the handle, spout, etc., and let it harden a bit before attaching (meanwhile keeping the pot wrapped up).

-When working with pieces where softer parts have been added to harder ones, wrap the whole piece up well in plastic and leave it alone for several days after the attachment. This will allow the piece time to even out in consistency before it dries. 

GLAZING- can be elating or depressing. Take notes on what you're doing, and keep an eye on other students' finished pots. Include observations about pots after each firing in your notebook, and write down what you do and don't like about your results. When you get results you don't like, figure out what went wrong. Is it the glaze, the way it was applied, the choice of glaze for the pot, or the firing? I think of glazing as being very much like learning a foreign language: when you are really starting to learn to speak it, you start to think in that language. Then you are glazing, you are speaking a visual language, applying something chalky and gray, but seeing in your mind's eye the beautiful, glossy color of the fired glaze. If you don't know anything about a glaze you shouldn't be using it.

Remember to wash your hands well after using glazes.

BE CURIOUS, ASK QUESTIONS, EXPERIMENT, HAVE FUN, READ, WORK HARD!