Ceramics info

In the beginning

Ceramics is one of the most ancient of all arts. It is also the most universal. Its existence is evidenced in relics of ancient man in the Stone Age of 10,000 to 20,000 years ago. It is found in the remains of nearly all tribes, races, and civilizations, from the most primitive to the most advanced, in all parts of the globe. The crude bowls of the prehistoric mound building Indians of North America, the funerary ware of pre-dynastic China, the brilliant votive goblets of antique Egypt, the magnificent vases of the Etruscans and of the early Greeks, the savage god-figures of Maya, and the tiled-floors of imperial Persia attest to its universality, and the degree to which the ceramic art had progressed at the dawn of recorded history. Ceramics made possible the magnificent glazed brick palaces of Ur, Babylon, and Nineveh in that cradle of civilization where the Tigris and Euphrates flow. It was here that clay became the medium of the written word in the form of cuneiform writing.
Each tribe, each race, each culture from the early beginnings to the present, developed its own peculiar ceramic forms and methods of decoration. At first, clay objects were crude, and used as utensils. It was but a step, as the means of scratching designs, painting colours, and adding glazes were discovered, to make these objects decorative as well as merely useful. Among some early peoples, characteristic forms and decorative artistry progressed to a point unequalled to this day. Many authorities contend that the degree to which the ceramic art was advanced is an index of the cultural level attained by each civilization.

It is not intended within this text to enlarge upon the almost infinite varieties of design and procedures evolved through the ages in the ceramic arts. These are the subjects of separate studies in this vast and intensely fascinating field. References are made only to illustrate basic procedures and techniques, so that the student may gain a practical knowledge of the simple fundamentals of ceramic art, proceeding from this point to more advanced work. The significant steps achieved in the history of ceramic art are mentioned, so that the student may have a better understanding of their derivation and the possibilities inherent in each.

Definition

Initially it should be made clear what we mean by ceramics. The name Ceramics, or Keramics (as it is often pronounced), is derived from the Greek word meaning "Potter's Earth." In a technical sense, then, ceramics includes all objects made from clay, or mixtures of clay with other substances, and baked or fired to hardness. These include china, porcelain, earthenware, stoneware, terra cotta, tile brick, clay pipe, clay shingle, etc.-in fact, all clay items of a purely practical nature as well as those which are ornamental.

However, in common usage, the term ceramics applies to the fine arts and concerns the esthetic and beautiful-the design, shaping, ornamentation, and decoration of items of clay. In this text we shall confine the definition of ceramics to this latter interpretation.

Universality of ceramics

At first thought, some people are apt to believe that ceramic items are of casual use and have only a limited application to everyday life. Reflect for a moment! Look about your home! Immediately, the tableware and dining service-plates, cups, saucers, bowls-come to mind. Then you note vases, flower pots, porcelain, statuettes, and lamp bases in the living room, the dining room, and bedroom. The bathroom-consider its tiles, washbasin, bathtub, and bowl! All these are ceramic! The kitchen sink, the white enamel stove, the refrigerator, are coated with ceramic material. Concealed, but still necessary, are the clay ducts for water supply, drainage, and waste. Perhaps there is a clay tiled roof. You thus become surprisingly aware that ceramics are necessary to civilized existence-and you then recognize that it provides both essential utility and beauty in your daily life.

Ceramics as an art

Ceramics permit the employment of all the plastic arts-design, composition, colour, painting, sculpture. The average person of average ability or talent can construct creditable pieces. The procedures are simple, readily understandable, and provide a wide range for creative ability. The play of imagination is without limit. The knowledge that the student has created something useful or something beautiful affords him the same thrill that the artist experiences when he realizes that he has succeeded in achieving his objective.

It must be pointed out that many useful pieces can be created as well as those which are merely ornamental. Further, history is replete with instances of individuals approaching the ceramic art as a means of recreation or diversion and finding it of such consuming interest that they have evolved new forms and decorative effects, and in so doing have achieved fame and fortune. Nor was an intensely technical education or long experience required-all that was needed was a feeling for clay, an imaginative expression in plastic form, and the willingness to study and thoroughly learn the fundamentals.

Clay

The entire art and industry of ceramics stems from the basic characteristics of clay. Clay is plastic-that is, it can be modelled or moulded when moist; it retains its form upon drying, and becomes rock-hard upon exposure to high temperature. When baked it is one of the most durable of all substances.

Clay consists primarily of microscopic particles of silica, alumina, and water in chemical combination. Many other chemicals comprising mainly earth oxides are found in clay which determine its colour, plasticity, firing properties, and economic usage.

In nature, clay may be formed at its point of origin through the action of subterranean water on certain types of rock. Other clays may occur as the result of water erosion and depositing of silt or sediment elsewhere. Boulder clays were formed by the grinding action of glaciers on rock during the Ice Ages, with the resultant fine rock flour becoming clay. China clay was made through the action of gases escaping from igneous rock upon certain minerals and rock materials. Some types of shale upon exposure to moisture become plastic clay.

Clay is mined in most instances. However, it is often found on the surface in a plastic condition, near streams, swamps, lakes, or other bodies of water. Primitive people invariably used wet surface clay found in the natural state, after removing grit and pebbles, for their pottery. The basic raw clays which have ceramic application are Kaolin, ball clay, and fire clay.

Kaolin, named after Kao-Ling, a hill in China, with which this type of clay was first identified, is a china clay which remains pure white after firing. It is the base for true porcelain. It has little plasticity, and other clays and rock derivatives, such as "petuntze," are often "blended" with it to give the desired plastic quality. It is found deposited in relatively few places in the world, and generally it requires processing to remove undesirable impurities.

Ball clay is a sedimentary clay, frequently found on the surface in a wet state. It has the quality of being highly plastic. When fired, the purer types of ball clays turn to a cream or stone grey colour.

Fire clays are often employed in the form of bricks to line kilns because they can withstand extremely high temperatures while supporting relatively heavy loads without collapsing.

There are numerous formulas for the proportion of ingredients to be mixed or blended to form the "bodies" of ceramic clays, each of which provides for different characteristics and often is a manufacturer's secret. Soft pottery or "soft pastes"-of which Greek vases, the cheaper earthenware, and majolica are examples-require relatively low temperatures for firing. Stoneware is much harder and requires longer periods of exposure to high temperature for proper firing. Porcelain requires the highest temperatures of all. The clay "body" of each of these has its own formula.

Clay for the student

Many processed and blended clays are readily available to the student from the numerous ceramic supply houses. Most shops that deal in art supplies have catalogues or can obtain information regarding firms from whom clays and other ceramic supplies may be procured. It is important, in ordering clay, to specify the colours, the form, and the use to which the clay is to be put.

Clay is sold in three forms: (1) dry, (2) plastic, and ( 3 ) casting slip.

Clay in the dry form may be converted to casting slip by the addition of water glass (sodium silicate) and water; to pasting slip by the addition of water only; or to plastic form by the addition of a smaller amount of water. However, plastic clay thus made must then be aged and "wedged." Aging results from permitting the moistened clay to remain idle for a time until thoroughly and uniformly moistened throughout. Wedging of plastic clay (the process of kneading or working plastic clay until it has a uniform consistency throughout and is free from air bubbles or pockets).

After a certain amount of wedging, clay purchased in the plastic form may be used for modelling or pressing. Casting slip is a mixture of clay, water glass, and water diluted to a consistency of very thick cream. Pasting slip is made by mixing clay and water to a consistency of cream. Casting slip is employed in casting clay objects in molds. Pasting slip is used as a medium for causing pieces of plastic or cast clay to adhere together. .

Methods of working clay

Clay objects may be constructed by the following methods

  • Modelling by Hand: Working clay in the plastic form into shape by using the fingers or hand tools.
  • Hand Pressing: Effected by pressing plastic clay into or around a hard object so that it takes the shape of the latter.
  • Casting: Accomplished by pouring casting slip into a prepared mold and removing the clay when it has dried to plastic condition.
  • Potter's Wheel: Certain types of clay objects may be constructed on a potter's wheel. In this procedure, clay of a consistency between casting slip and plastic form is placed ("thrown") on the centre of a horizontal revolving wheel and is gradually formed up into a circular vase or bowl shape by hand.

Basic sequence

Generally the basic sequence for making a ceramic object is as follows:

  1. Constructing the clay object while the clay is in moist condition. This includes the methods of working clay as indicated in the previous paragraphs, and of clay ornamentation by various methods.
  2. Drying the object to a bone-dry state.
  3. Firing the bone-dry object to bisque; first firing.
  4. Applying glaze, or under glaze colour and glaze, to the bisque object. Step 5. Firing the glaze (and under glaze colour if used) on the object; second firing.
  5. Applying over glaze colour on the glazed object.
  6. Firing the over glaze on the object; third firing.

Ceramics:
  • Index
  • Coil method
  • Decoration
  • Glaze decoration
  • Glossary
  • Hand pressing
  • Kiln & firing
  • Mould making
  • Plastic & flower
  • Potters wheel
  • Slab method
  • Slip casting

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