1. Not Your Ordinary “Mud”

3. Clay is......a fine mixture of decomposed igneous rock minerals and organic matter Igneous Rock

4. 1.Melted rock is cooled and solidified into igneous rock (mother rock) which makes up earth’s crust. 2.Mechanical weathering over millions of years breaks down the rock from boulders into stones, to pebbles to fine, small particles known as platelets. Weathering

5. 1.Freezing and thawing 2.Grinding of glaciers 3.Pounding of rain 4.Flow of rushing streams 5.Probing of tree roots 6.Acidic reactions with decomposed organic matter (chemical weathering)

6. ...aids in moving particles away from the site of origin resulting in 2 types of clay deposits.

7. 1.Primary Clays 2.Secondary Clays

8. 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)

9. 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

10. 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

11.  Gray to tan or brown when moist  Non-translucent  Matures at 2232-2381 degrees F.  Vitrifies = non-porous  Pinkish color when bisque  Very durable = dinnerware safe  Used by Burke Pottery

12. 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

13. REMEMBER: E.S.P. EarthenwareStonewarePorcelain

15. Plasticity Shrinkage Porosity Aging Wedging Vitrification

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

18. 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

19. AGING, WEDGING, & ADDING MOISTURE

20. 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.

21. 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.

22. 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.

24.  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.

25. 1.Water between clay particles moves to the surface and evaporates 2.Clay particles move closer together until touching. 3.Shrinkage stops and remaining water between pores evaporates. Tip: Drying should occur more slowly during stages A and B as seen in the diagram

26. 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.

27. 1.Make a cylinder 5” tall and 5” in diameter with ½” thick walls for each clay body. 2.Place the cylinder on a piece of paper, tracing around the base. 3.Measure and record the exact diameter, height, and thickness of the wall. 4.Re-measure the form after firing. Subtract the difference and divide by the original wet measurements to get the percentage of shrinkage. Optional: Make a 2” x 11”x 1/2” slab. Score a 10” line down the middle. Measure and divide the difference by 10 to get the shrinkage rate.

28. 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.

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

31. 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.

33. Kiln Cone Slurry Wet Leatherhard Greenware Bisqueware Glazeware

34. Clay may be recycled up through greenware stage.

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

36. 8-12 hours to heat + 8-12 hours to cool 16-24 hours for firing cycle

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

38. After the clay has been fired it CANNOT be recycled!

39. 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