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Module: 6
Lecture: 27 Whitewares
Dr. N. K. Patel
Module: 6
Lecture: 27
WHITEWARES
Whiteware are made by mixing china clay, feldspar and flint (SiO2) with or
without Whiteware having good strength, translucency and very low porosity can be
obtained by firing the products at 1450-15000C. Whitewares contain refractory body
and glassy coating known as the glaze. There is a corresponding variation in the
degree vitrification due to different amount of fluxes.
1. WHITEWARES
They are available in number of special types such as floor tiles, resistant to
abrasion, glazed or unglazed, impervious to stain penetration and wall tiles.
CLASSIFICATION
a) Earthenware
It is also known as semi-vitreous dinnerware which is porous, non-translucent
and soft glaze.
b) Chinaware
It is a vitrified translucentware with a medium glaze which resists abrasion and
used for non-technical application.
c) Porcelain
It is vitrified translucentware with a hard glaze which resists abrasion to a
maximum degree and may include chemical, insulating and dental porcelain.
d) Sanitaryware
It was made from clay which is porous but nowadays vitreous composition is
used. Prefired and sized vitreous grog is include with triaxial composition
e) Stonewares
They are the oldest ceramicwares which is used before porcelain. It is known
as crude porcelain but its raw materials are of poor grade and not well fabricated.
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Module: 6
Lecture: 27 Whitewares
Dr. N. K. Patel
MANUFACTURE
Kaolin Water
Water
Filter Press
Felspar
Casting
Grinder
Slurry
Furnace
Reactor
Water
Decoration
Gaze
Article
White
Wares
Dilution Tank
Figure: Manufacturing of White Wares
Block diagram of manufacturing process
Diagram with process equipment
Animation
It involves three steps
 Body of ware
 Glaze
 Decoration
Body of ware
Kaolin and feldspar are reduced to fine powder then suspended in the form
of cream. Then excess water is removed by filter press. By use of resulting the paste,
article can be obtained after moulding, are dried slowly and fired to get
porousware which is known as bisque.
Glaze
Porous article is covered with glaze to get water tight article which is done by
melting it over the surface of the body. Quartz, feldspar, boric oxide are the
constituent of the glaze which are finely ground and mixed with water which forms
slip then it is fired to higher temperature to produce smooth and glossy surface. The
glaze must be chose in such a way that resist the reagents and must have same coefficient of expansion as the body; otherwise the vessel which is exposed to change
of temperature will crack.
Decoration
Design may be painted on the body before glazing using metal oxide or
painted upon the glaze using coloured glass and article is fired so, the pigment melts
into glaze. It painted upon glaze then known as over glazed.
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Module: 6
Lecture: 27 Whitewares
Dr. N. K. Patel
Applications
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Dishes
Crucibles
Spark plug
Electrical insulator
Laboratory equipment
Glazing
It is mixture of glass forming materials which is in form of fine powder e.g. lead
silicates, borosilicate etc. If mixture free from iron and colouring pigments then forms
colourless glaze.
Metal oxides
The following metal oxides are used for producing the colour to glaze.
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Iron oxide: Brown colour
Iron oxide and lime: Cream colour and yellowish tint
Copper oxide: Green colour
Cobalt blue: Blue colour
Requisite of glazing
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To provide smooth, glossy surface to treated materials
To protect the surfaces from the environmental or atmospheric actions
To produce decorative effect
To make the surface impervious to liquid, water etc.
To improve appearance and durability of the article
Method of glazing
a) Salt glazing
b) Liquid glazing
a) Salt glazing
Sodium chloride is used to get glossy film over the earthenwares. Sodium
chloride is throwing to furnace where articles are in red hot condition. Due to heat
salt volatilize and react with silica which makes glossy film of sodium chloride.
b) Liquid glazing
Liquid glazing is much superior then salt method in which fine powder of glaze
mixture, colouring pigments are mixed with water to form a colloidal solution known
as slip glaze. The article is then burnt in kiln at low temperature. Then it is dipped into
glaze slip so the glaze materials fill up the pores of articles. To fuses and forming thin
glossy film, articles are fired into the kiln. Care should be taken that firing articles
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Module: 6
Lecture: 27 Whitewares
Dr. N. K. Patel
does not comes in contact with direct fire, otherwise soot & dust should discoloured
the article. Delicated articles should be burnt in muffle furnace which is heated
externally while articles are kept inside.
PROPERTIES
 A traditional ceramic used to make pottery and porcelain. While, whiteware
ceramics often have a glassy structure.
 Any of a broad class of ceramic products that are white to off-white in
appearance and frequently contain a significant vitreous, or glassy,
component.
 Imperviousness to fluids, low conductivity of electricity, chemical inertness,
and an ability to be formed into complex shapes. These properties are
determined by the mixture of raw materials chosen for the products, as well
as by the forming and firing processes employed in their manufacture
USES
Whitewares find application in spark plugs, electrical insulators, laboratory
equipment, crucibles, dishes, and high-class potteries. Including products as diverse
as fine china dinnerware, lavatory sinks and toilets, dental implants, and spark-plug
insulators
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