techniques of pottery

• Glazing pictures?

• Difference between Under glazed & Un glazed?

• Difference between Engraving & Carved relief ?

ARTS

CERAMICS

• Ceramics (noun and adjective) are those things made from materials which are permanently changed when heated.

• Changes are on the molecular level, which also changes the physical characteristics of the object.

• A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling.

Ceramic materials may have a crystalline or partly crystalline structure, or may be shapeless (e.g., a glass).

• Unlike metals and glass, pottery(ceramics) can not be melted down and re-used - once broken, it is thrown away. Also unlike metals, it can not rust/decay, and unlike wood and other materials, pottery can not rot. Hence it is generally the most common find on a particular archaeological site.

• Because clay is easy to shape and decorate, pottery always reflects contemporary tastes and cultural ideals and so it is an ideal subject of art-historical study. Different shapes and decorations were used at different times, by different people, and for different purposes. So by studying pottery, archaeologists can date their sites and say a great deal about ancient cultures. It provides information about technology, industry, art, diet and a host of other attributes of ancient cultures.

Firing

• Kiln

Glaze• It is a glassy coating on pottery, the primary

purposes of which are decoration and protection. • One important use of glaze is to render porous

pottery vessels impermeable to water and other liquids.

• It may be applied by dusting the unfired composition over the ware or by spraying, dipping, trailing or brushing on a thin slurry composed of the unfired glaze and water.

• The color of a glaze before it has been fired may be significantly different than afterward. To prevent glazed wares sticking to kiln furniture during firing, either a small part of the object being fired (for example, the foot) is left unglazed used as supports. These are removed and discarded after the firing.

• Glazes are the most often used form of pottery decoration. They come in a huge variety, including nearly every color imaginable and many types of textures.

Slip

• Slip tailing is one of the most widely known and used methods of decorating with slip. Slip trailing delivers a stream of slip to damp or leather-hard clay through some type of dispenser.

• This dispenser can be a large-bore syringe (needle) such as a bottle with a nozzle such as used for condiments or glue. In either case, the dispenser's opening must be wide enough so that it won't easily clog. In addition, the slip used consist of fairly fine particles also, again in order to reduce clogging.

• A slip is a suspension in water of clay and/or other materials used in the production of ceramic ware. sodium silicate, can be added to the slip to disperse (defuse, solve, go away) the raw material particles.

• This allows a higher solids content to be used.• It combined with glazed often to make decorative

effect. like icing to a cake.• There are many interesting and diverse pottery

decorating techniques involving the use of slips. Effects range from very linear to very textural, and from very fluid to quite hard-edged.

Types

• Earthenware• Stoneware• Porcelain ware

Earthenware

• The earliest forms of pottery were made from clays that were fired at low temperatures in pit-fires or in open bonfires.

• They were hand formed and undecorated. Because the bisque (base or main) form of earthenware is porous, it has limited utility for storage of liquids.

Stoneware

• Glazed Stoneware was being created as early as the 15th century BCE in China. This achievement coincided with kilns that could be fired at higher temperatures

• Called stone ware because of its stone like character. They are dense than earthen ware.

• They are in grey but after firing turn into brown

Porcelain ware

• Chinese ware• Made of white Chinese clay• Opaque (not clear, dense) than stone ware

Methods of decoration of ceramics

1. Painting

1. Enamel/over glazed/Minai wareApplied to fired clay body already coated with the fire glazed2. Under glazed ware Used on fired but unglazed body 3. Luster ware Over the glazed

Under glazed painting

• The color mainly made of “Gosu” (cobalt oxide) is used in under glazed decoration.

• The decorative techniques include drawing, shading (dami), transfer printing, stamping and blowing.

• The term “Under glaze” means a picture is drawn under the glaze.

• Under glazed ceramics made only use of gosu are called “Tempu”.

Luster ware

• Luster-painting is a unique contribution of the

Islamic world. • It became an important paint for ceramics

from about 800AD, but was used on glass in Egypt and Iraq before this date.

• Luster pigment is a compound of silver, copper and iron oxide in a refractory earth kept together by gum.

• It is applied to the glazed surface of a previously fired vessel.

• The painted object is then refried to a red heat in a reducing atmosphere in the small specially constructed kiln used only for this purpose.

• In the second "firing" the metals are bonded to the glaze as a thin layer with a strongly metallic luster, the refractory earths can then be brushed off.

Glazed/Minai ware

Probably one of the most beautiful types of Iranian pottery that was produced during the Seljuq period is that of overglaze-painting. In Persian the names of mināi (enamel), or haft-rangi, (seven colours) are used.

• Pour the glaze over the clay and fire the piece in a gas kiln.

• The glaze comes in different colors and textures besides white, such as turquoise, black and lapis lazuli (dark blue). They can be used according to product lines.

• There are two kinds of firing techniques: oxidation and reduction. They form color changes on the fired piece.

• The clay shrinks about 10 % when it is fired, and becomes very hard.

• In the case of porcelain, the body becomes less absorbent, white and more transparent.

2. Cutting or incising

a) Sgraffito b) Engraving c) Carved relief

Sgraffito

• Sgraffito (noun) is the technique of incising down through a layer of applied slip to the clay body below, in which the clay and slip are of contrasting colors.

• The term is from the Latin for scratch (as with a stylus) which is also the root for "graffiti" and "graphic" (as in to write).

Engraving

• To carve, cut, or etch into a material

Carved relief

• The cutting of material such as stone or wood to form a figure or design.

• A figure or design formed by this kind of cutting.

Moulding & modeling

Moulds

Modeling

Unglazed