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Distinguishing Earthenware, Stoneware and Porcelainby Bill Zemon, "On Location Correspondent for CeramicsEcuador.com" Owning a fine piece of decorative
ceramics is to hold a piece of history in your hands. Pottery
is one of the oldest and most widespread of the decorative arts.
The basic materials and techniques used to create a vase, flask
or bottle can find their roots in the work done by artisans thousands
of years ago. The raw material of all ceramic is under our feet.
The earth The molding of clay into useful and attractive shapes is one of the oldest and most widespread of the decorative arts. Mankind discovered early in his existence that one of the three basic kinds of soil had the capability of retaining the shape into which it was molded. At some point the firing process was developed wherein the potter,s work became durable, never losing its form even when immersed in water for long periods. In addition, fired clay resisted all corrosive and destructive influences that would destroy other materials such as metals or wood. These properties made pottery an instant hit with the homeowner for wet or dry storage. Since pottery involves such a close relationship between the potter and his work, ancient to the artistic expression of the human hand as applied to the marvelous substance that is clay. Clay is a fine-grained natural material,
which along with sand and loam, make up the principal three elements
of soil. Potter's clay is a mixture of true clay (mostly hydrous
aluminum silicates) and other elements such as feldspar, quartz,
mica, iron oxides or other elements. As you might imagine, since
the composition of the clay will vary, so also will its plasticity,
color and other characteristics. The Andes mountain range of
Ecuador is almost all clay, and here we find local craftsmen
hand forming red bricks and roof tiles which naturally obtain
their color from the iron oxides of the clay. The Yapacunchi
Studios prepare their own clay mixture, It is the firing process that brings a whole new range of qualities to the raw clay. Placing the unbaked clay in the sun makes it firm enough to handle without damage, but for an enduring product, the pottery must be kept in an oven for many hours and brought to a temperature of at least 900 degrees Fahrenheit. Sun baked clay that is exposed to water will eventually lose it,s shape, but fired clay becomes almost indestructible (but not unbreakable!). A fired clay vessel can hold acids and alkalines, and no amount of exposure to water will cause it to lose its shape. In this rather simple process, raw earth is transferred into something truly marvelous. The level of temperature reached during the firing process has been used to distinguish various forms of the potter,s art. If enough heat is applied (2900 degrees Fahrenheit), even plain clay will turn to glass. Mixing the clay with other substances that vitrify at a lower temperature produces STONEWARE. When clay is mixed with feldspar and fired at temperatures between 2000 and 2650 degrees Fahrenheit, we find the pottery becomes translucent, and is called PORCELAIN. Clay that is fired, but has not vitrified can be called EARTHENWARE. All vitrified pottery has a tendency to chip easily. The distinction between porcelain and stoneware is not always clear. Both porcelain and stoneware must reach the point of vitrification. Those pieces when held to the light allow some light to pass are considered translucent. In western countries, this translucent quality distinguishes porcelain from stoneware. However this is not always the case. Certain thin stoneware pieces that have been fired at a high temperature are slightly translucent, and heavily cast porcelain can be opaque. In China, the distinction between stoneware and porcelain is determined by the ring or tone produced when the object is tapped. Thus, the terms porcelain and stoneware are descriptive rather than definitive. Earthenware is the most ancient of the potter's art, and is still widely used. Since much of the earthenware used in this modern age is heat-proof and cold-proof, it is extremely popular for use in the kitchen. The decorative items produced by Yapacunchi Ceramics, since they are not fired to the point of vitrification, are also termed earthenware. Stoneware is very hard and includes delicate works of art as well as the well-known Ironstone introduced in England in the early 19th century. Porcelain originated in China, where the process was kept secret from the west until the early 18th century. Bone china is produced by adding bone ash to the clay mixture resulting in a ivory colored product. Bone china is preferred in American households for dinnerware as it is strong and chip resistant. The value of a work of art is not derived from the materials or techniques that are used in its production, but rather in the response evoked in the eye of the beholder. Our appreciation of the artist's expression can be enhanced with knowledge of his processes. The true test of a work of art is the form, color and design, which inspires admiration and satisfaction in us. |
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