Emily Lees Frontier Elementary Pinellas County [email protected] Ceramics 101 Earliest Ceramics: 24,000- 29,000 BCE -Dolni Vestonice, Moravia (Czech Republic) Earliest Pottery: 18,000 BCE- Jiangxi China Kiln Usage Tips: Ø Don’t load ware onto the firebrick bottom of your kiln. Start each load with short stilts and a kiln shelf. Ø Ware should not touch the sides of the kiln or the kiln shelf stilts. Ø Greenware may be stacked- be careful not to create a seal between pieces. Ø If glazed ware becomes fused to something else break it free with an abrupt bump. Ø Kiln wash your shelves- paint it on and fire alone once before firing ware on it. Kiln wash allows glaze drips and fusions to pop off easily. Ø Do not fire your kiln overnight. Ø Do not open the kiln until it is close to 100° F. Ø On glaze firing avoid loading a shelf close to the kiln lid. Ø Vacuum out you kiln every once in a while. Ø Pin back loose electric coils in the kiln. 5 Ways to Prevent Explosions During Bisque Firing: 1) Air dry pieces as long as possible. 2) Make a hole in hollow forms 3) Don’t build thicker that 1”. 4) Pre-heat/ Candle Fire 5) Fire Slowly Best Heat-Work Practices: 1) Your bisque fire must be slow and accurate 2) The correct temperature for low-fire bisque is cone 04 3) Glaze Firing is best done at cone 05 My Essential Tool List: Ø Toothpicks Ø “Stabby” Cheap Plastic Forks Ø Blending Tools or Color Shapers Ø Fettling Knife and Needle Tool (replace with chopsticks, tongue depressors or toothpicks) Ø Scupting Thumb or Rounded Dowel Ø Canvas or Canvas Pad of Paper Ø Finger Bowls Ø Spray Bottle Ø Rolling Pins or Dowels Ø Slab Roller or Slats/Pencils Ø Stamps, Stamp Rollers, Stamping Mats Ø Ribbon Tools Procedural Tips: Ø Start small. Ø Try your clay projects first. Ø Make visual steps Ø For one-day projects consider demonstrating and planning the week before. Ø Cut clay into portions for the project ahead of time Ø Make supplies easy to pass out. Ø Plan for storage when wet and for organization and storage while drying. A Bunch oF DeFinitions: Ball Clays- Can be mixed with other clays to increase plasticity Bisqueware- Biscuit- Unglazed clay body fired to low temperature- typically cone 04- about 1945° F Bisque Firing- The process of firing clay that has not been fired yet. During this firing clay becomes ceramic Candle (verb)- To fire a clay body very slowly or at very low temperatures to aid in drying Ceramics- The art of making and firing clay bodies Clay- A stiff, sticky fine-grained earth that can form a cohesive mass and retain a shape when molded Coil- Clay rolled into wet rope-like pieces Cone- A ceramic pyramid that melts at a known temperature and is used to shut off the kiln at a certain temperature. Earthenware- A low fire clay body, usually fired between 06 and 04 Englobe (interchangeable with Slip)- A slurry of clay that may be colored with glass or frit Fire- to cook or bake in a kiln Fire Clays- High fire clays with a speckled appearance- most often added to stoneware to increase tooth (roughness) and maturation temperature Foot- the part of a ceramic object that touches the kiln shelf Glaze (Noun)- a ceramic paint typically composed of opaque or transparent colors which becomes vitreous when fired to maturity (Verb)- the act of applying ceramic paint Glaze Firing- Typically the second firing of a ceramic body after glaze has been applied Gloss- A shiny finish Greenware- Any unfired clay body before it is bisque fired- very fragile Grog- bisqueware that has been ground up into little pieces and is added to wet, workable clay to make clay hold its shape better, reduce shrinkage and make ware less likely to crack Hand Building- Sculpting any clay body by hand Heat Work- All the work of heating and cooling the clay Incise- Indenting into the clay Kiln- an oven for burning, baking or drying and in this case for firing pottery Leather Hard- Clay that is partly dried, is not flexible/can’t take impressions, but can still be joined to another piece of clay Maturity/ Maturation- Clay that fired to correct temperature at the right speed is said to be “mature” Matte- Non-shiny finish Peephole- a hole or holes in a kiln that is usually covered with a peephole plug. Can be looked through to see ware or cones Plasticity- a term used to describe a clay’s workability and ability to hold a shape (highly plastic=easy to work with) Porcelain (Kaolin)- A high fire clay body- Cone 5-10 Pottery- Pots, dishes and other functional containers made of clay Score- to rough the surface of wet clay to aid in attaching another piece Shrinkage- All ceramics shrink between 4-15% when drying and in the firing process Stoneware- A high fire clay body that fires to maturity between 2150-2336° F Terra Cotta- A low fire red clay- literally means “baked earth” Underglaze- A colored liquid clay paint that is applied to greenware or bisqueware and often coated with a clear coat Ware- a catch-all term for everything made of clay What Happens to Clay in the Kiln During a Bisque Firing Stage 1: Atmospheric Drying 180-200° F Candle Fire SLOW 212° The Boiling Point of Water/ Atmospheric Water Evaporates Clay Compacts a Little Stage 2: Burn Off Carbon, Sulfur and 572-1470° F If These Cannot Burn Away Carbon Coloring Occurs Organics Stage 3: Chemically Bonded H2O 660-1470° F After Atmospheric Drying Clay Contains 14% Chemically Bonded Burned Off H2O- It Burns Off Here- Clay Gets Lighter SLOW Stage 4: Quartz Inversion Occurs 1060° F Silica Oxide is also known as Quartz- The Crystalline Structure of SLOW Quartz Changes/Inverts Here Expanding 2% While Heating and Contracting 2% When Cooling Stage 5: Sintering 1650° Clay Particles Fuse=Called Sintering- This is When Clay “Becomes” Ceramic Stage 6: Vitrification and Maturity 1850-2135° F Cone 06-3 –Earthenware 2160-2290° F Cone 4-7 –Mid-Range 2315-2535° F Cone8-14 –High-Fire Vitrification=Process Where Some Materials Melt and Fill in Spaces Between Other Particles Creating Hardness and Durability Maturity= When the Vitrification is Just Right Mullite Crystals (Aluminum Silicate) Bind and Strengthen the Ware Cooling 1650° Quartz Inversion SLOW 420° F Cristobalite (Crystaline Silica) Hits a Sudden Phase of Shrinking .