Transcript Introduction to Clay

Introduction to Clay
Experiencing Clay Chapter 1-3
Vocabulary
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Ceramic
Raw Clay
Throwing
Hand Building
Plastic
Glaze
Score
Slip
Firing
Kiln
Traditional Pottery
Wedging
Kneading
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Pinch
Coil
Extruder
Slab
Mold
Slab Roller
Drape Mold
Slump/Press Mold
Drying
Shrinkage
Bone Dry
Leather Hard
Green Wear
Chapter 1
• What is Clay?
– Clay is the result of break down of the earth’s
rock. Weather, ice, Water and the crust
movement breaks down granite rock and part
of the granite is the basis for clay.
Early uses for Ceramics
• To embellish or add a
visual element to a
story
• Religious ritual
• Effigies
(representation of a
person in
remembrance)
• Containers to store
crops, water, seeds.
• Bowls to eat and drink
out of.
• Pots to cook with.
4 methods to forming clay pieces:
1.
2.
3.
4.
Pinching
Coiling
Slab Building
Molding
Why is it important to control the
speed that your clay piece dries.
• If your clay dries to fast I may crack and break.
• Some parts of your clay may be thinner than
others and may dry at different rates. This can
also cause your clay to separate or crack.
• If your clay dries too fast it is not workable any
more.
• You may also need to let some of your pieces
harden a little to make them more substantial
while you build your form.
Decorating Techniques
• Incising: carving or cutting the surface with
a sharp tool.
• Impressing: using an object to press or
stamp a design into the clay.
• Combing: marking the surface of the clay
with uniform lines.
• Burnishing: rubbing and polishing the
surface with a smooth stone or hard wood.
Chapter 2
• What are the different Clay Properties?
– Plasticity
– Shrinkage
– Texture
– Moisture
Plasticity
• It is easier to work with plastic clay.
• This property is dependent on the amount
of water and other compounds that are in
the clay.
Shrinkage
• As your clay piece looses water it will
shrink.
• Firing your piece will cause it to shrink
even more.
(the clay we use will shrink about 12%)
Texture
• The texture of the clay will depend on the
additives in the clay.
• Some clay will have other materials in it to
make it stronger.
• Different textures of clay are used for
different projects. (you need to use a
smother clay to make useful pottery so
that it will be hard and water tight.)
Moisture
• All clay contains water
• You can add water to rehydrate the clay and make it more plastic
again.
• Too much water makes the clay loose plasticity and turn into a liquid.
• You may need to rehydrate your clay as you work.
• When you are not working you need to cover your clay with a plastic
bag to keep the moisture in.
• The only way to get all of the water out of your clay is to fire it.
• Thick walls may hold moisture pockets in them. The trapped
moisture will turn to steam and expand. This expansion will cause
the pocket to explode in the kiln.
• Once the clay is fired it is permanently hardened and can not be
made plastic again.
Stages of Drying
Kneading and Wedging
use these techniques to get air bubbles out of clay after it has been over worked or to mix water into
dryer clay.
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Kneading
Form a loaf shape
Tear or cut in half
Slam back together
Stand above and use
your body weight to
push down.
Wedging
• Use both hands at the
same time to lift,
rotate and press the
clay.
Drape and Slump Molds
use molds to hold your clay in position while it dries
Drape Mold
Slump Mold
Lay your clay over the mold and form it into the
shape you want. The mold will hold it in
place while it dries.
Lay or press your clay down into the mold. (also
called Press Molds)
Pinch Pot:
form the clay into a vessel shape by making a ball, Pushing your thumb into the center of the ball and
then using your thumb and fingers in a pinching motion to form the walls.
Coiling
rolling out long snake like pieces of clay and then joining them together to build your clay piece.
Slabbing
rolling out flat pieces of clay to be used to build your clay form.