Advanced Ceramics

1. Advanced Ceramics VOCABULARY

2. Vitrification • Fired clay that has fused together completely, so that the pores between refractory particles are filled with glass and the body is impervious to water. • Reaches temperature maturity,turns into a glass like substance, and loses all porosity.

3. Placticity • The property of clay that allows it to change shape without rupturing when force is applied to it. Plasticity of potter’s clay cannot be measured by any scientifically repeatable test. Therefore its measurement is subjective.

4. Flocculation • The process very small particles like clay exhibit in forming loose clumps due to weak electrostatic attraction between the particles. These clumps are called flocs or agglomerates.

5. Porosity • The ability to absorb water. High temperature low porosity. Food safe pots have low • porosity, planters usually have high porosity.

6. Kiln • A specialized oven or furnace used for firing clay for pottery. An oven on steroids.

7. grog • sand or ground fired clay added to clay to decrease shrinkage and its tendency to crack • when drying. Grog helps toughen clay. Except for porcelain, all clay has varying degrees of grog • and you can add grog to porcelain too.

8. Stoneware • 2300 – 2430 (cones 6 – 10) • White to dark brown • Varies smooth to rough • Smooth, usually very workable

9. Earthenware • 1680 – 2050 (cones 010 – 03) • white or terra cotta (brick) red • Varies smooth to Rough • smooth, usually very workable

10. Porcelain • Highest firing usually 2400 – 2430 (cones 9 – 11) • Pure White • Very smooth • Very smooth but touchy to throw subject to cracking

11. Primary clay • Clays that remains at the site of the parent rock, without being transported by wind or water—tend to be free of contaminants but have coarse particle size and therefore low plasticity. Includes the purest kaolins.

12. Secondary clay • Clays that have been transported away from their point of geologic origins by wind or water. Finer particle-size gives greater plasticity—ball clays, stoneware clays, fireclays, etc

13. bisqueware • Initial kiln firing in which clay sinters without vitrifying, and though very porous, will no longer soften in water.

14. greenware • Any dry, unfired clay form

15. glazeware • Product after kiln firing in which glazes are melted to form a smooth glassy surface

16. leatherhard • Condition of clay in which it has stiffened but is still damp. Point at which pieces are joined and most surface modification and trimming are done. Soft leather-hard ideal for forming, joining, thick slip-decorating. Medium leather-hard good for thin slip- decorating, joining, incising, carving, piercing. Hard leather-hard good for thin slip- decorating, carving, scraping

17. slip • Clay suspended in water, usually the consistency of thick cream. May be colored and used to decorate surfaces, or may be cast into plaster molds to create ceramic forms.

18. wedge • Process of kneading the clay with the hands to remove air bubbles and ensure homogenous mass.

19. Pinching • Handbuilding method where clay objects are formed by pinching repeatedly between thumb and fingers or between fingers of one hand and palm of opposing hand.

20. Coil method • Ceramic forming method utilizing ropelike coils of plastic clay, assembled in successive courses to build up wall of vessel or sculpture.

21. sgraffito • Decorating technique achieved by scratching or carving through a layer of slip or glaze (helps to apply wax-resist over glaze before carving) before firing to expose contrasting claybody beneath.

22. intaglio • Decorating technique where design is formed by cutting or carving shallow lines in clay surface. Also known as incising

23. platelets • Flat, thin crystals that make up clay. When wet they become sticky and slippery, creating the phenomenon we call plasticity

24. plano • Surface decoration where the surface remains flat.

25. alto • Surface decoration where the decoration is raised.

26. glaze • Coating of powdered ceramic materials, usually prepared and applied in water suspension, which melts smooth and bonds to clay surface in glaze firing.

27. underglaze • Colored slips formulated to have low drying shrinkage, allowing application to bone-dry or bisque-fired surface before glazing. Commercial underglazes are available in a wide palette of colors primarily for low-fire, but many will survive high-fire

28. compression • In wheel throwing, the act of hand or finger pressure on the clay, resulting in lower moisture content and a denser structure. Lack of compression in bottoms of pots can result in S-cracks

29. Stilting • Term often applied to all kiln posts, but more correctly referring to specialized refractory furniture pieces equipped with ceramic or metallic points designed to support fully glazed wares during firing.

30. Dry footing • Wiping the bottom of ware so there is no trace of glaze. Bare bisque does not stick to kiln shelves, glaze does.

31. crazing • Very fine surface cracks in fired glaze surface—technically a fault in glazed wares, but often sought after, especially in raku

32. crawling • Glaze fault where glaze recedes away from an area in the firing, leaving bare clay. Usually caused by dusty, dirty, or oily surface beneath glaze or by excessively powdery glaze. In some cases results from very high L.O.I. in glaze materials, causing high glaze-shrinkage and resulting cracking during firing. Used intentionally in controlled crawl and beading glazes

33. Slip casting The creation of ceramic forms by casting slip in plaster molds.

34. calipers Adjustable tool for measuring inside/outside diameters, as in making lids.

35. Coefficient of expansion A measurement of a material’s tendency to expand when heated and contract when cooled. The higher the coefficient of expansion, the lower the thermal shock resistance. In firing dissimilar materials in contact with one another the coefficient of expansion must be matched.

36. Collaring (necking in) Process of reducing the upper diameter of a thrown form by working the walls of the rotating form inwards with fingers or rib, as in a bottle shape.

37. Iron oxide Fe2O3—powdered rust—refractory red in oxidation, converts to black iron (flux) in reduction and/or high-fire.

38. slaking The process of returning dry unfired clay to a slip by soaking in water.

39. Pyrometric cones • Small slender pyramidal-shaped indicators made of ceramic material formulated to bend at a specific temperature—standard method for determining maturing temperature of firing. Like clay and glazes, cones respond to temperature, duration, and atmosphere of firing far more accurately than mechanical measurement

40. Banding wheel Hand-operated turntable for applying wax resist and banded decoration.

41. bat Rigid flat disc of wood, plastic, or plaster placed on wheelhead. When throwing is finished, bat is lifted off wheelhead, avoiding damage or warpage.

42. annealing The process of cooling a heated object gradually to allow internal shrinkage stress to equalize without damage.

43. extruder Machine that forces plastic clay through a die to produce extruded clay shapes.

44. Wheel wedging Working the clay up and down in a cone shape on the wheel to align the platelets in a spiral formation and thus increase control in centering and throwing.

45. Fracture Plane Fracture zone that results when clay components are pressed straight together without disrupting the surface (by scoring and adding slurry or by smearing together) to intermix the platelets. Parts hold together while wet and tacky, but will separate easily when dry or fired.

46. Decoration with Textures • Impressing - • Incising - • Applique - • Piercing - • Burnishing - • Inlaying – Incising and adding different pieces of clay within the surface of the clay. • Sprigging - • And… Decorating technique where textured or patterned material or object is pressed into clay surface. Decorating technique where design is formed by cutting or carving shallow lines in clay surface. Low-relief clay shapes added to scored, slurried leather-hard surface for decoration. Using any tool to poke any type of hole in clay surface. Method of achieving a shine by rubbing clay or slip with smooth hard object. Surface decorating technique in which small coils or balls of clay are affixed to the damp or leather-hard surface, usually with a layer of slip.

47. Decoration with Color • Value – Light and darkness of color – adding white for tint, adding black for shades. • Colored clay – Incorporating colored, powdered stains into clay to alter the base color • Inlaying - Incising and adding different pieces of clay within the surface of the clay. • Oxides –Chemical compounds with oxygen used to alter color. • Carbonates - Chemical compounds with carbon used to alter color. • Colored slips – Liquid colored clay. • Underglaze/Engobe - • Glazes • And… Colored slips formulated to have low drying shrinkage, allowing application to bone-dry or bisque-fired surface before glazing. Commercial underglazes are available in a wide palette of colors primarily for low-fire, but many will survive high-fire.

48. Decoration with Techniques • Sponging - Decoration technique using the surface of different types of sponges to apply glazes or slips. • Splattering - Decoration technique applying glazes or slips by splashing or sputtering onto clay surface. • Brushing - Decoration technique using any type of paintbrush. • Masking - Decoration technique • Paper resist - Decoration technique where strips of moist or adhesive paper are adhered to the surface to resist application of slip or glaze. • Tape or Wax resist – Used in glazing and decorating that can be applied to surface to prevent adhesion of slip or glaze. • Slip trailing - Application of decoration to wet or leather-hard clay by flowing on lines of slip w/fine pointed dispenser, such as a syringe. • Sgraffito - Decorating technique achieved by scratching or carving through a layer of slip or glaze (helps to apply wax-resist over glaze before carving) before firing to expose contrasting claybody beneath. • Glaze resist -Decorating technique where resist materials are applied to prevent glaze from adhering to certain areas. • Mishima - East Asian method of creating an inlaid effect by applying contrasting slip into a design incised in leather-hard clay. When the slip stiffens, the excess is scraped off. • Terra sigillata (terra sig) -Ultra refined clay slip that can give a soft sheen when applied to bone-dry wares and if polished or burnished while still damp may give a high gloss. All ancient Greek red-black pottery and Roman red wares were finished with this technique, without the use of glaze. • Stencil – Using a shaped form to either add or obstruct glazes and slips to the surface of clay. • And…

49. Decoration with printing • Transfer printing • Monoprints • Photo emulsions • Computer-generated decal transfers • And…