Not Your Ordinary “Mud”

Objects made from any type of clay that is fired with the aid of heat

Dates back to when mankind first learned to control fire Anthropologists use Stone Age clues to piece together a variety of possible theories.

1.Primary Clays 2.Secondary Clays

Clays which remain at the site (mother rock) where they were formed. Fewer impurities Coarser grained texture (less weathered) Highly refractory (resistant to heat/high fire) Low plasticity (harder to work with) Whiter fired color (Porcelain)

Bright white clay – very pure Translucent (light passes through) High Fire – matures at 2419 degrees F. A very hard clay Vitrifies = non-porous Smooth – very fine, not as plastic Feels very dry (harder to throw) Still white when bisque

Clays which have been transported by wind, glacier, water, etc. away from site of origin Finely ground (more weathered) Contaminated with organic matter More plastic Stoneware & Earthenware

 Gray to tan or brown when moist  Non-translucent  Matures at degrees F.  Vitrifies = non-porous  Pinkish color when bisque  Very durable = dinnerware safe

Reddish brown clay that matures at a low temperature (approximately 1830 degrees, which is red hot heat.) Also known as terra cotta (baked earth) Flower pot clay Remains porous Does not vitrify

REMEMBER: E.S.P. EarthenwareStonewarePorcelain

Plasticity Shrinkage Porosity Aging Wedging Vitrification

1.Plasticity 2.Shrinkage 3.Porosity These 3 properties must be considered before choosing a clay body.

The ability to hold together while being shaped (workability) Does it stretch and bend without breaking? Test It! Wrap a coil around your finger. If it cracks, the clay is not plastic. Plastic Not Plastic Create the Coil

AGING, WEDGING, & ADDING MOISTURE

Storing well mixed clay for 3 plus weeks which causes a chemical breakdown of the organic matter contained in the clay. Older is better! Historical Fact: The Chinese aged clay for whole generations.

1.Aligns clay particles 2.Equalizes moisture 3.Removes air bubbles 4.Makes clay texture uniform Tip: You should always wedge first before using your clay.

All clay contains water. Clay dehydrates when exposed to air. Add water to clay to make it more plastic. Too little or too much water causes clay to become less plastic. Tip: Mist clay with water bottle or dampen it with a wet sponge. Always wrap your projects with plastic before storing.

 Contraction of clay (or glaze) during both drying and firing processes.  Clay shrinks 12-15%  Shrinkage depends on the clay body’s composition. Tip: It is important to understand the shrinkage of your clay body since it has a tendency of cracking and warping during this process.

1.When a drying tile rests on a smooth surface, the upper face will dry first. 2.The tile will curl up because the upper face is smaller than the lower face (uneven shrinkage). 3.Later when the tile is completely dry the curl remains as the body is too rigid to completely straighten out. Tip: In addition to warping, uneven shrinkage may also cause cracking. These defects may be prevented with slow overall drying or delay the drying of certain parts by covering.

If the shrinkage rate is 10%, then the final glaze- fired piece of any object made from that clay body will only be 90% of the original wet clay size.

The capacity of a clay body to absorb moisture Based on the amount of space in the structure of the fired clay body

High Porosity allows more water into or through clay body. Keep it inside during the winter and use a trivet to protect your coffee table! Low Porosity, or vitrified clay, allows little or no water into or through the clay body. Vitrification: When a clay is fired to its maturing temperature it loses its porosity and transforms into a hard, nonabsorbent, glasslike state.

Kiln Cone Slurry Wet Leatherhard Greenware Bisqueware Glazeware

Clay may be recycled up through greenware stage.

 The Kiln is a chamber to heat clay  It creates chemical changes to the clay and glazes which create greater strength and permanency

8-12 hours to heat hours to cool hours for firing cycle

Porcelain White Hot Heat 2400 degrees F. Stoneware 2200 degrees F Earthenware or Bisqueware Red Hot Heat 1800 degrees F.

After the clay has been fired it CANNOT be recycled!

1. Slurry (potter’s glue): Liquid clay 2. Wet/Soft: Plastic clay 3. Leatherhard: not easily distorted, maintains form and can be smoothed, carved, and added to 4. Greenware (bone-dry): Water is evaporated; form is brittle 5. Bisqueware: once-fired, maintains porosity 6. Glazeware: fired more than once, vitreous

Pinch Pots

Coil Pots

Slab Built

RibLoopWire Fettling Knife Wood Modeling Tool Needle