| Today there are many options for putting colorful | | | | silica. This clay composition accounts for the pure |
| patterns onto porcelain china. Some, like | | | | white gleam of porcelain. |
| decoupage, waterslide decals and air-dry paints like | | | | Artisans who paint porcelain (rather than actually |
| Delta Air-Dry PermEnamel are within the reach of | | | | make it) refer to three grades of porcelain: |
| any home crafter. | | | | hard-paste, soft-paste, and bone china. They all |
| Others, like dye sublimation printing, transfer | | | | contain kaolin but only hard-paste has feldspar and |
| printing and hand-glazing high-fired pottery require | | | | silica and is high-fired. The high temperatures |
| substantial investment in equipment and are best | | | | cause the body and the glaze to fuse. When |
| suited to well-capitalized businesses and artists' | | | | hard-paste porcelain is broken, it is impossible to |
| cooperatives. | | | | distinguish the body from the glaze. |
| The two classic ways of putting patterns onto | | | | Soft-paste porcelain adds ground glass or frit |
| porcelain, hand-painting and transfer printing, still | | | | (material for glass that is not yet fused and |
| exist today. In addition, there is a high-tech | | | | vitrified) and is fired to between cone 01 and 1 |
| version of waterslide decals used commercially | | | | (1999 to 2109 degrees F). Because soft-paste |
| which consists of screen-printing decals with | | | | porcelain is fired at lower temperatures, it does |
| glazes and applying the decals to the porcelain. In | | | | not completely vitrify and remains slightly porous. |
| each case, the pottery is high-fired before | | | | When soft-paste porcelain is broken, you can |
| decorating to at least cone 6. [Cone is a measure | | | | distinguish a grainy body covered with a glassy |
| of heat absorption resulting from heat applied | | | | layer of glaze. |
| over time. Cone 6 translates to between 2165 | | | | Bone china has bone ash added to the kaolin and |
| and 2269 degrees F (depending on how fast the | | | | vitrifies (becomes glass-like) somewhere between |
| kiln heats - or ramps - up).] Such high-firing | | | | cone 2 and cone 5 (2034 to 2205 F). Though not |
| produces the hard almost-translucent quality of | | | | as hard as true porcelain, bone china is more |
| genuine porcelain. Then the piece is decorated and | | | | durable than soft-paste porcelain. The bone ash |
| lightly fired repeatedly to melt and fuse the glazes | | | | greatly increases the translucence of the porcelain. |
| to the porcelain. | | | | Finally, go to a tile store and look at their |
| Incidentally, the term "porcelain" has been applied | | | | "porcelain" tiles. If you turn them over, you will |
| more and more broadly as new techniques | | | | see base clay ranging from white to brown to |
| developed. Ask any potter to define "porcelain" | | | | gray. The definition of "porcelain" in the tile |
| and he will likely give you the classic definition. To | | | | industry has nothing to do with the clay content |
| a potter, genuine porcelain is high-fired (cone 6 or | | | | or level of firing. Rather, tile manufacturers define |
| higher) white clay that is at least somewhat | | | | as "porcelain" any tile fired to the point where it |
| translucent. It has a large proportion of kaolin clay, | | | | absorbs less than 3% moisture. |
| with the remainder being primarily feldspar and | | | | |