Title of Invention	"A COMPOSITION USEFUL FOR PROVIDING PROTECTIVE AND DECORATIVE COATING ON TERRACOTTA AND EARTHENW ARE ARTICLES"
Abstract	A composition useful for making coating materials for providing protectective and decorative coating on terracotta and earthenware articles which comprises: Name of the constituents Amount in Wt. % Common clay 85-98 Red oxide 1-15 Talc 1-10 Boric acid 1-5 Black stain 1-10 Borax 0-6 Soda lime glass 1-40 Flint glass 1-40 Lead bisilicate 0-5 Green stain 1-10 Oxides and halides of transition metals 0-10

Title of Invention

"A COMPOSITION USEFUL FOR PROVIDING PROTECTIVE AND DECORATIVE COATING ON TERRACOTTA AND EARTHENW ARE ARTICLES"

Abstract

A composition useful for making coating materials for providing protectective and decorative coating on terracotta and earthenware articles which comprises: Name of the constituents Amount in Wt. % Common clay 85-98 Red oxide 1-15 Talc 1-10 Boric acid 1-5 Black stain 1-10 Borax 0-6 Soda lime glass 1-40 Flint glass 1-40 Lead bisilicate 0-5 Green stain 1-10 Oxides and halides of transition metals 0-10

Full Text	The present invention relates to a composition useful for providing protective and decorative coating on terracotta and earthenware articles. The process of the present invention particularly relates to the use of wide variety of common clay with colourant and colour transfer for making coating materials called bonok with wide ranging applicability. The main usage of the bonok is in the field of common clay wares and terracotta bodies for inparting the articles more imperviousness to moisture and water, glossiness, colour of choice and elegance and decor. The said articles may also be used as roofing tiles, wall tiles, cooking wares, art objects and allied and related items. The present day method of making bonok essentially consists of using particular variety of clay available in selected places directly or after beneficiation of such clay by various processes. Two such clays are separately taken, mixed with sufficient quantity of water in a container and hand blunged thoroughly so that the clay materials are dispersed with or without adding some dispersing agents. This mixture is then left for 24 hrs for thorough dispersion of the clay as well as for settling of the coarse particles at the bottom. Next day, the liquid in the form of a vary thin slurry containing very fine particles of clay is decanted into another container. The two clays in the slurry form are mixed together and left for ageing for 4 to 7 days. The slurry is then screened through a fine cloth to remove any coarse material. The screened liquid is finally boiled or sun dried to reduce the volume to about one-third of the original volume and then directly used on the green articles as coating material called bonok for which references may be made to "Status of Rural pottery in India" - A Bastar Scenario, T. K. Mukhopadhyay and T. K. Dan, Indian J. Rural Technology, 7( 1 & 2) 1995, 63-76., "Coloured Engobes for Roofing Tiles", I. Ivanov et al, Interbrick, Vol. 5, No. 3,1989, pp 20-21., "Preparation and application of Eagobes", the final report on technology UPGRADATION for production of terracotta figurines and garden articles utilising locally available raw materials in the District of Bastar, M. P., Submitted to CSIR, Sept 1996, pp. 23-24, leading to a product with narrow application range and insufficiency in quantity in comparison to the amount of initial raw materials taken. Bonok is also made by other process very similar to this process. The main draw backs of the above processes may be listed as below. 1. Any available common clay is not suitable for making bonok. 2. Properties of the coating developed after firing has no flexiability. 3. The process is rigidly dependent on the specificity of raw materials. 4. Percentage yield of bonok is exceedingly low. S. Nature of the raw materials determines the colour of the final product The main object of the present invention is to provide a process for making coating material for providing protective and decorative coating on terracotta articles which obviate the drawbacks as detailed above. Another object of the present invention is to utilise non clay materials in addition to clay for making the coating material. Still another object of the present invention is to eliminate the need to depend on a particular type of clay for making the coating material. Yet another object of the present invention is to provide a coating material that imparts different colours to the finished articles. Still another object of the present invention is to provide a coating material mat imparts glossiness to the finished articles. Yet another object of the present invention is to provide a coating which imparts imperviouaness to the finished articles. Still another object of the present invention is to provide a coating having enhanced scratch resistance. Yet another object of the present invention is to provide a coating which makes terracotta products resistant to moisture. Still another object of the present invention is to provide a coating which makes the terracotta products resistant to weather. Yet another object of the present invention is to provide a coating which makes the terracotta products resistant to water. Still another object of the present invention is to provide a coating which decorates the terracotta products. Accordingly, the present invention provides a composition useful for providing protectective and decorative coating on terracotta and earthenware articles which comprises: Name of the constituents Amount in wt. % Common clay 85-98 Red oxide 1-15 Talc 1-10 Boric acid 1-5 Black stain 1-10 Borax 0-6 Soda lime glass 1-40 Flint glass 1-40 Lead bisilicate 0-5 Green stain 1-10 Oxides and halides of transition metals 0-10 The composition obtained by the process of the present invention is neither a product of chemical reaction nor a mere admixture but is a synergistic formulation having properties different than the aggregate properties of the individual components Accordingly, the present invention provides a process for making coating material useful for providing protective and decorative coating on terracotta and earthenware articles which comprises proportioning and thorough mixing and grinding the above composition with common clay in the presence of 150 to 300 wt. % water of total solid content to obtain a slurry, sieving the said slurry through 400 mesh BS, mixing 0.01 to 0.2 percent sodium carbonate and 0.02 to 0.4 percent sodium silicate of total solid content to the slurry so obtained followed by ageing for a period in the range of 6 hrs to 36 hrs.. In an embodiment of the present invention wherein the thorough mixing and grinding may be effected for a period of 12 hours to 72 hours by grinding and ball milling using porcelain or aluminium oxide balls of diameter 1 cm to 5 cm or by attrition milling using porcelain or aluminium oxide balls of diameter 0.1 cm to 0.3 cm. In another embodiment the grinding and ball milling or attrition milling may be effected using porcelain aluminium oxide balls 2 to 4 times the weight of the solid material content In still another embodiment colouring compounds may be introduced in clay batch and thorough mixing may be effected by milling. Yet in another embodiment of the present invention colour transfer may be introduced on the fired articles. Accordingly the present invention provides a process for making coated articles using the coating material prepared by the process of the present invention which comprises application of coating slurry on unfired terracotta/earthenware articles by known methods such as spraying, dipping or painting, drying the coated articles so obtained at a temperature hi the range of 80° C to 105° C for a period in the range of 4 hrs to 24 hrs and firing at a temperature in the range of 850° C to 1250°C for a period in the range of 0.5 hrs to 3 hours. The details of the process of the present invention are given below: A) Common clay is mixed with different constituents like red oxide, talc, boric acid, black stain, borax, soda lime, flint glass powder, green stain, lead bisilicate, oxides and halides of transition metals, in the range of 0.00 percent to 50 wt percent, either alone or in combination with one another. B) The mixed materials are charged in a pot mill or attrition mill along with water in the range of 150-300 wL% of total solid C) Porcelain or alumina balls of size in the range of 1 • 5 cm, having weight in the range of 2 to 4 times the weight of the solid are put in the pot mill or porcelain or alumina balls of size in the range of 0.1 to 0.3 cm, having weight in the range of 3 - 4 times the weight of the solid are put in the attrition mill. D) Pot mill or attrition mill is run for a period in the range of l2 - 72 hours. E) After milling the milled material is sieved to separate grinding balls. F) Sodium carbonate in the range of 0.01 to 0.2% and sodium silicate in the range 0.02 to 0.4 wt% are mixed with the shiny and kept for a period in the range of 6 - 36 hrs. for ageing. O) The shiny so produced is the coating material called bonok is applied on unfired articles by dipping, spraying or painting. H) Coated articles are dried at a temperature in the range 80° C - 105° C for a period in the range 4 -24 hours. I) Dried articles are fired at a temperature in the range of 850° C -1250° C for a period in the range of 0.5 - 3 hours. The process of the present invention can be used to produce coated terracotta and earthen ware of various shapes and sizes required for application as art object, roofing tiles, wall tiles, utility wares and cooking wares. Common clay contains all the essential ingredients for producing articles of common use. The coating material or bonok is essentially a finer fraction of clayey material with required amount of fluxes to produce sufficient liquid phase at the firing temperature to give reduced pore microstructure retaining enough mechanical and thermo mechanical properties for the use suggested. Since the main body of the articles and the coating material applied on its surface belongs to the same class of material, homogeneous bonding with matching thermo mechanical properties characterises the system. Colourant introduced in the form of inorganic compounds in the system as amorphous, crystalline or in glassy state, will act as colour centre and will generate derived colour texture on the surfaces of the produced articles. Except the difference in particle size between coating material and the material of the body, no other parameters vary to a great extent as a consequence of which the coating and the main body of the article tends to assume a homogeneous monolithic structure improving the properties of the material as a whole. The characteristics of the common clays used in the examples are given in table-1: Designation and source of day (Table Removed) The following examples are given by way of illustration of the present invention and should not be construed to limit the scope of the present invention. 500 gm of common clay (Table 1; clay no. 1) together with 100 gm red oxide and 1000 ml of water are wet milled for 24 hours in 5000 ml pot using 2 kg of porcelain ball of diameter 1 cm, 2 cm and 3 cm in the ratio of 1:1:2. The slurry produced is sieved through 400 mesh B.S and porcelain balls were separated. 0.06g sodium carbonate and 1.8 g sodium silicate are mixed with the shiny and stirred vigorously and kept for 24 hrs in a covered vessel. This shiny is applied on unfired articles made from common clay by dipping. The articles after polishing are dried at 90° C for 12 hrs. Dried articles are fired at 1000 °C for 2hrs. 100 g of common clay (Table 1; clay no. 2) together with 20 g of red oxide and 200 ml of water are milled for 24 hrs in an attrition mill of size 500 ml with 300 g porcelain balls of size 1.5 mm. The slurry thus produced is sieved through 400 mesh B.S and porcelain balls were separated. 0.06 g sodium carbonate and 0.3 g sodium silicate are mixed with the slurry and stirred vigorously. The entire material is kept in a covered vessel for 20 hrs. This slurry is applied on unfired articles made from common clay by spraying. The sprayed articles after polishing are dried at 90° C for 4 hrs. Dried articles are fired at 1000° C for 2 hours. 250 gm of common clay (Table 1; clay no. 1) together with 240 gm of another day (Table 1; clay no. 6), 10 gm talc and 750 ml of water are wet milled for 18 hours in 2500 ml pot using 1 kg of porcelain balls of diameter 2 cm, 3 cm and 5 cm in the ratio of 1:2:1. The shiny produced is sieved through 400 mesh RS and porcelain balls were separated. 0.06 g sodium carbonate and 0.10 g sodium silicate is mixed with the slurry and stirred vigorously and kept for 12 hrs in a covered vessel. This slurry is applied on unfired articles made from common clay by spraying. The sprayed articles after polishing are dried at 90° C for 24 hrs. Dried articles are fired at 1100 °C for 1 hour. 490 gm of common clay (Table 1; clay no. 4) together with 5 gm talc, 5 gm lead bisilicate and 1000 ml of water are wet milled for 12 hours in 5000 ml pot using 1 kg of porcelain balls of diameter 1.5 cm, 3 cm and 4 cm in the ratio of 1:2:1. The slurry produced is sieved through 400 mesh B.S and porcelain balls were separated. 0.08 g sodium carbonate and 1.6 g sodium silicate are mixed with the slurry and stirred vigorously and kept for 18 hrs in a covered vessel. This slurry is applied on unfired articles made from common clay by spraying. The sprayed articles are dried at 90° C for 24 hrs. Dried articles are fired at 950 ° C for 1 hour. Example 5 100 g of common clay (Table 1; clay no. 3) together with 25 g of black stain, 25 gm of window glass and 250 ml of water are milled for 24 fare in an attrition mill of size 1000 ml with 300 g porcelain balls of size 1.0 mm. The shiny thus produced is sieved through 400 mesh B.S and porcelain balls were separated. 0.03 g sodium carbonate and 0.3 g sodium silicate are mixed with the slurry and stirred vigorously. The entire material is kept in a covered vessel for 24 hrs. This starry is applied on unfired articles made from common clay by allaying. The sprayed articles are dried at 90° C for 6 hrs. Dried articles are fired at 1250° C for 1 hour. 500 gm of common clay (Table 1; clay no. 2) together with 150 gm transparent frit, 100 gm of borax and 1500 ml of water are wet milled for 36 hours in 5000ml pot using 1.5 kg of porcelain balls of diameter 2 cm, 3 cm and 4 cm in the ratio of 1:1:1. The shiny produced is sieved through 400 mesh B.S and porcelain balls were separated. 0.05 g sodium carbonate and 1.80 g sodium silicate are mixed with the slurry and stirred vigorously and kept for 36 hrs in a covered vessel. This slurry is applied on unfired articles made from common clay by spraying. The sprayed articles are dried at 90° C for 24 hrs. Dried articles are fired at 1200 ° C for 2 hours. 500 gm of common clay (Table 1; clay no. 7) together with 50 gm red oxide, 50 gm of borax and 1000 ml of water are wet milled for 12 hours in 5000 ml pot using 1.5 kg of porcelain balls of diameter 1 cm,3 cm and 4 cm in the ratio of 1:1:2. The shiny produced is sieved through 400 mesh B.S and porcelain balls were separated. 0.10 g sodium carbonate and 1.5 g sodium silicate are mixed with the slurry and stirred vigorously and kept for 10 hrs in a covered vessel. This slurry is applied on unfired articles made from common clay by spraying. The sprayed articles are dried at 90° C for 24 hrs. Dried articles are fired at 1050 ° C for 3 hours. Example 8 50 g of common clay (Table 1; clay no. 1) together with 25 g of transparent frit, 25 gm of window glass and 200 ml of water are milled for 60 hrs in an attrition mill of size 1000 ml with 300 g porcelain balls of size 1.0 mm. The slurry thus produced is sieved through 400 mesh B.S and porcelain balls were separated. 0.08 g sodium carbonate and 1.20 g sodium silicate are mixed with the slurry and stirred vigorously. The entire material is kept in a covered vessel for 24 hrs. This shiny is applied on unfired articles made from common clay by spraying. The sprayed articles are dried at 90° C for 6 hrs. Dried articles are fired at 1050° C for 2 hours. 500 g of common clay (table-1; clay no. 9) together with 150 g of transparent frit and 100 g of borax and 1000 ml water are wet milled in a pot mill of size 2500 ml with 1.5 kg porcelain balls of diameter 2 era, 3 cm and 4 cm in the ratio of 1:1:1 . The pot mill is run for 24 hours. 0.10 g sodium carbonate and 0.4 g sodium silicate are mixed with the slurry and stirred vigorously. The slurry produced is sieved through 400 mesh B.S. and porcelain balls were separated. The entire material is kept in a covered vessel for 18 hours. This slurry is applied on unfired articles made from common clay by dipping. The dipped articles are dried at 100°Cfor 18hrs. Dried articles are fired at 1100° C for 2 hours. Colour transfer are applied on the surface of the fired articles and re fired at 750° C. The main advantages of the present invention are: 1. Wide flexibility of the process that accommodates common clay of any origin to produce the coating material for application on earthenware or terracotta bodies. 2. Yield is more than 90% 3. Colour and texture of the coating can be monitored by changing the composition of the raw materials. 4. Surface properties of the ware may be improved by improving the quality of the coating. We Claim: 1. A composition useful for providing protectective and decorative coating on terracotta and earthenware articles which comprises: Name of the constituents Amount in Wt. % Common clay 85-98 Red oxide 1-15 Talc 1-10 Boric acid 1-5 Black stain 1-10 Borax 0-6 Soda lime glass 1 -40 Flint glass 1-40 Lead bisilicate 0-5 Green stain 1-10 Oxides and halides of transition metals 0-10 2. A composition useful for providing protective & decorative coating on terracotta & earthenware articles substantially as herein described with reference to the examples.

Full Text

The present invention relates to a composition useful for providing protective and decorative coating on terracotta and earthenware articles. The process of the present invention particularly relates to the use of wide variety of common clay with colourant and colour transfer for making coating materials called bonok with wide ranging applicability.
The main usage of the bonok is in the field of common clay wares and terracotta bodies for inparting the articles more imperviousness to moisture and water, glossiness, colour of choice and elegance and decor. The said articles may also be used as roofing tiles, wall tiles, cooking wares, art objects and allied and related items.
The present day method of making bonok essentially consists of using particular variety of clay available in selected places directly or after beneficiation of such clay by various processes. Two such clays are separately taken, mixed with sufficient quantity of water in a container and hand blunged thoroughly so that the clay materials are dispersed with or without adding some dispersing agents. This mixture is then left for 24 hrs for thorough dispersion of the clay as well as for settling of the coarse particles at the bottom. Next day, the liquid in the form of a vary thin slurry containing very fine particles of clay is decanted into another container. The two clays in the slurry form are mixed together and left for ageing for 4 to 7 days.
The slurry is then screened through a fine cloth to remove any coarse material. The screened liquid is finally boiled or sun dried to reduce the volume to about one-third of the original volume and then directly used on the green articles as coating material called bonok for which references may be made to "Status of Rural pottery in India" - A Bastar Scenario, T. K. Mukhopadhyay and T. K. Dan, Indian J. Rural Technology, 7( 1 & 2) 1995, 63-76., "Coloured Engobes for Roofing Tiles", I. Ivanov et al, Interbrick, Vol. 5, No. 3,1989, pp 20-21., "Preparation and application of Eagobes", the final report on technology UPGRADATION for production of terracotta figurines and garden articles utilising locally available raw materials in the District of Bastar, M. P., Submitted to CSIR, Sept 1996, pp. 23-24, leading to a product with narrow application range and insufficiency in quantity in comparison to the amount of initial raw materials taken. Bonok is also made by other process very similar to this process. The main draw backs of the above processes may be listed as below.
1. Any available common clay is not suitable for making bonok.
2. Properties of the coating developed after firing has no flexiability.
3. The process is rigidly dependent on the specificity of raw materials.
4. Percentage yield of bonok is exceedingly low.
S. Nature of the raw materials determines the colour of the final product
The main object of the present invention is to provide a process for making coating
material for providing protective and decorative coating on terracotta articles
which obviate the drawbacks as detailed above.
Another object of the present invention is to utilise non clay materials in addition to
clay for making the coating material.
Still another object of the present invention is to eliminate the need to depend on a
particular type of clay for making the coating material.
Yet another object of the present invention is to provide a coating material that
imparts different colours to the finished articles.
Still another object of the present invention is to provide a coating material mat
imparts glossiness to the finished articles.
Yet another object of the present invention is to provide a coating which imparts
imperviouaness to the finished articles.
Still another object of the present invention is to provide a coating having enhanced
scratch resistance.
Yet another object of the present invention is to provide a coating which makes
terracotta products resistant to moisture.
Still another object of the present invention is to provide a coating which makes the
terracotta products resistant to weather.
Yet another object of the present invention is to provide a coating which makes the
terracotta products resistant to water.
Still another object of the present invention is to provide a coating which decorates the
terracotta products.
Accordingly, the present invention provides a composition useful for providing
protectective and decorative coating on terracotta and earthenware articles which
comprises:
Name of the constituents Amount in wt. %
Common clay 85-98
Red oxide 1-15
Talc 1-10
Boric acid 1-5
Black stain 1-10
Borax 0-6
Soda lime glass 1-40
Flint glass 1-40
Lead bisilicate 0-5
Green stain 1-10
Oxides and halides of transition metals 0-10
The composition obtained by the process of the present invention is neither a
product of chemical reaction nor a mere admixture but is a synergistic formulation having properties different than the aggregate properties of the individual components
Accordingly, the present invention provides a process for making coating material useful for providing protective and decorative coating on terracotta and earthenware articles which comprises proportioning and thorough mixing and grinding the above composition with common clay in the presence of 150 to 300 wt. % water of total solid content to obtain a slurry, sieving the said slurry through
400 mesh BS, mixing 0.01 to 0.2 percent sodium carbonate and 0.02 to 0.4 percent
sodium silicate of total solid content to the slurry so obtained followed by ageing
for a period in the range of 6 hrs to 36 hrs..
In an embodiment of the present invention wherein the thorough mixing and
grinding may be effected for a period of 12 hours to 72 hours by grinding and ball
milling using porcelain or aluminium oxide balls of diameter 1 cm to 5 cm or by
attrition milling using porcelain or aluminium oxide balls of diameter 0.1 cm to 0.3
cm.
In another embodiment the grinding and ball milling or attrition milling may be
effected using porcelain aluminium oxide balls 2 to 4 times the weight of the solid
material content
In still another embodiment colouring compounds may be introduced in clay batch
and thorough mixing may be effected by milling.
Yet in another embodiment of the present invention colour transfer may be
introduced on the fired articles.
Accordingly the present invention provides a process for making coated articles
using the coating material prepared by the process of the present invention which
comprises application of coating slurry on unfired terracotta/earthenware articles
by known methods such as spraying, dipping or painting, drying the coated articles
so obtained at a temperature hi the range of 80° C to 105° C for a period in the
range of 4 hrs to 24 hrs and firing at a temperature in the range of 850° C to 1250°C for a period in the range of 0.5 hrs to 3 hours.
The details of the process of the present invention are given below:
A) Common clay is mixed with different constituents like red oxide, talc, boric
acid, black stain, borax, soda lime, flint glass powder, green stain, lead bisilicate,
oxides and halides of transition metals, in the range of 0.00 percent to 50 wt
percent, either alone or in combination with one another.
B) The mixed materials are charged in a pot mill or attrition mill along with water
in the range of 150-300 wL% of total solid
C) Porcelain or alumina balls of size in the range of 1 • 5 cm, having weight in the
range of 2 to 4 times the weight of the solid are put in the pot mill or porcelain or
alumina balls of size in the range of 0.1 to 0.3 cm, having weight in the range of
3 - 4 times the weight of the solid are put in the attrition mill.
D) Pot mill or attrition mill is run for a period in the range of l2 - 72 hours.
E) After milling the milled material is sieved to separate grinding balls.
F) Sodium carbonate in the range of 0.01 to 0.2% and sodium silicate in the range
0.02 to 0.4 wt% are mixed with the shiny and kept for a period in the range of 6 -
36 hrs. for ageing.
O) The shiny so produced is the coating material called bonok is applied on unfired articles by dipping, spraying or painting.
H) Coated articles are dried at a temperature in the range 80° C - 105° C for a period in the range 4 -24 hours.
I) Dried articles are fired at a temperature in the range of 850° C -1250° C for a period in the range of 0.5 - 3 hours.
The process of the present invention can be used to produce coated terracotta and earthen ware of various shapes and sizes required for application as art object, roofing tiles, wall tiles, utility wares and cooking wares.
Common clay contains all the essential ingredients for producing articles of common use. The coating material or bonok is essentially a finer fraction of clayey material with required amount of fluxes to produce sufficient liquid phase at the firing temperature to give reduced pore microstructure retaining enough mechanical and thermo mechanical properties for the use suggested. Since the main body of the articles and the coating material applied on its surface belongs to the same class of material, homogeneous bonding with matching thermo mechanical properties characterises the system. Colourant introduced in the form of inorganic compounds in the system as amorphous, crystalline or in glassy state, will act as colour centre and will generate derived colour texture on the surfaces of the produced articles. Except the difference in particle size between coating material and the material of the body, no other parameters vary to a great extent as a
consequence of which the coating and the main body of the article tends to assume
a homogeneous monolithic structure improving the properties of the material as a
whole.
The characteristics of the common clays used in the examples are given in table-1:
Designation and source of day

(Table Removed)
The following examples are given by way of illustration of the present invention and should not be construed to limit the scope of the present invention.
500 gm of common clay (Table 1; clay no. 1) together with 100 gm red oxide and 1000 ml of water are wet milled for 24 hours in 5000 ml pot using 2 kg of porcelain ball of diameter 1 cm, 2 cm and 3 cm in the ratio of 1:1:2. The slurry produced is sieved through 400 mesh B.S and porcelain balls were separated. 0.06g sodium carbonate and 1.8 g sodium silicate are mixed with the shiny and stirred vigorously and kept for 24 hrs in a covered vessel.
This shiny is applied on unfired articles made from common clay by dipping. The articles after polishing are dried at 90° C for 12 hrs. Dried articles are fired at 1000 °C for 2hrs.
100 g of common clay (Table 1; clay no. 2) together with 20 g of red oxide and 200 ml of water are milled for 24 hrs in an attrition mill of size 500 ml with 300 g porcelain balls of size 1.5 mm. The slurry thus produced is sieved through 400 mesh B.S and porcelain balls were separated. 0.06 g sodium carbonate and 0.3 g sodium silicate are mixed with the slurry and stirred vigorously. The entire material is kept in a covered vessel for 20 hrs.
This slurry is applied on unfired articles made from common clay by spraying. The sprayed articles after polishing are dried at 90° C for 4 hrs. Dried articles are fired at 1000° C for 2 hours.

250 gm of common clay (Table 1; clay no. 1) together with 240 gm of another day (Table 1; clay no. 6), 10 gm talc and 750 ml of water are wet milled for 18 hours in 2500 ml pot using 1 kg of porcelain balls of diameter 2 cm, 3 cm and 5 cm in the ratio of 1:2:1. The shiny produced is sieved through 400 mesh RS and porcelain balls were separated. 0.06 g sodium carbonate and 0.10 g sodium silicate is mixed with the slurry and stirred vigorously and kept for 12 hrs in a covered vessel.
This slurry is applied on unfired articles made from common clay by spraying. The sprayed articles after polishing are dried at 90° C for 24 hrs. Dried articles are fired at 1100 °C for 1 hour.
490 gm of common clay (Table 1; clay no. 4) together with 5 gm talc, 5 gm lead bisilicate and 1000 ml of water are wet milled for 12 hours in 5000 ml pot using 1 kg of porcelain balls of diameter 1.5 cm, 3 cm and 4 cm in the ratio of 1:2:1. The slurry produced is sieved through 400 mesh B.S and porcelain balls were separated. 0.08 g sodium carbonate and 1.6 g sodium silicate are mixed with the slurry and stirred vigorously and kept for 18 hrs in a covered vessel. This slurry is applied on unfired articles made from common clay by spraying. The sprayed articles are dried at 90° C for 24 hrs. Dried articles are fired at 950 ° C for 1 hour.
Example 5
100 g of common clay (Table 1; clay no. 3) together with 25 g of black stain, 25 gm of window glass and 250 ml of water are milled for 24 fare in an attrition mill of size 1000 ml with 300 g porcelain balls of size 1.0 mm. The shiny thus produced is sieved through 400 mesh B.S and porcelain balls were separated. 0.03 g sodium carbonate and 0.3 g sodium silicate are mixed with the slurry and stirred vigorously. The entire material is kept in a covered vessel for 24 hrs. This starry is applied on unfired articles made from common clay by allaying. The sprayed articles are dried at 90° C for 6 hrs. Dried articles are fired at 1250° C for 1 hour.
500 gm of common clay (Table 1; clay no. 2) together with 150 gm transparent frit, 100 gm of borax and 1500 ml of water are wet milled for 36 hours in 5000ml pot using 1.5 kg of porcelain balls of diameter 2 cm, 3 cm and 4 cm in the ratio of 1:1:1. The shiny produced is sieved through 400 mesh B.S and porcelain balls were separated. 0.05 g sodium carbonate and 1.80 g sodium silicate are mixed with the slurry and stirred vigorously and kept for 36 hrs in a covered vessel. This slurry is applied on unfired articles made from common clay by spraying. The sprayed articles are dried at 90° C for 24 hrs. Dried articles are fired at 1200 ° C for 2 hours.
500 gm of common clay (Table 1; clay no. 7) together with 50 gm red oxide, 50 gm of borax and 1000 ml of water are wet milled for 12 hours in 5000 ml pot using 1.5 kg of porcelain balls of diameter 1 cm,3 cm and 4 cm in the ratio of 1:1:2. The shiny produced is sieved through 400 mesh B.S and porcelain balls were separated. 0.10 g sodium carbonate and 1.5 g sodium silicate are mixed with the slurry and stirred vigorously and kept for 10 hrs in a covered vessel. This slurry is applied on unfired articles made from common clay by spraying. The sprayed articles are dried at 90° C for 24 hrs. Dried articles are fired at 1050 ° C for 3 hours.
Example 8
50 g of common clay (Table 1; clay no. 1) together with 25 g of transparent frit, 25 gm of window glass and 200 ml of water are milled for 60 hrs in an attrition mill of size 1000 ml with 300 g porcelain balls of size 1.0 mm. The slurry thus produced is sieved through 400 mesh B.S and porcelain balls were separated. 0.08 g sodium carbonate and 1.20 g sodium silicate are mixed with the slurry and stirred vigorously. The entire material is kept in a covered vessel for 24 hrs. This shiny is applied on unfired articles made from common clay by spraying. The sprayed articles are dried at 90° C for 6 hrs. Dried articles are fired at 1050° C for 2 hours.
500 g of common clay (table-1; clay no. 9) together with 150 g of transparent frit and 100 g of borax and 1000 ml water are wet milled in a pot mill of size 2500 ml with 1.5 kg porcelain balls of diameter 2 era, 3 cm and 4 cm in the ratio of 1:1:1 . The pot mill is run for 24 hours. 0.10 g sodium carbonate and 0.4 g sodium silicate are mixed with the slurry and stirred vigorously. The slurry produced is sieved through 400 mesh B.S. and porcelain balls were separated. The entire material is kept in a covered vessel for 18 hours.
This slurry is applied on unfired articles made from common clay by dipping. The dipped articles are dried at 100°Cfor 18hrs. Dried articles are fired at 1100° C for 2 hours.
Colour transfer are applied on the surface of the fired articles and re fired at 750° C. The main advantages of the present invention are:
1. Wide flexibility of the process that accommodates common clay of any origin to
produce the coating material for application on earthenware or terracotta bodies.
2. Yield is more than 90%
3. Colour and texture of the coating can be monitored by changing the composition
of the raw materials.
4. Surface properties of the ware may be improved by improving the quality of the
coating.

We Claim:
1. A composition useful for providing protectective and decorative coating on terracotta
and earthenware articles which comprises:
Name of the constituents Amount in Wt. %
Common clay 85-98
Red oxide 1-15
Talc 1-10
Boric acid 1-5
Black stain 1-10
Borax 0-6
Soda lime glass 1 -40
Flint glass 1-40
Lead bisilicate 0-5
Green stain 1-10
Oxides and halides of transition metals 0-10
2. A composition useful for providing protective & decorative coating on terracotta &
earthenware articles substantially as herein described with reference to the examples.

Documents:

336-del-1999-abstract.pdf

336-del-1999-claims.pdf

336-del-1999-correspondence-others.pdf

336-del-1999-correspondence-po.pdf

336-del-1999-description (complete).pdf

336-del-1999-form-1.pdf

336-del-1999-form-19.pdf

336-del-1999-form-2.pdf

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Patent Number

232880

Indian Patent Application Number

336/DEL/1999

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

21-Mar-2009

Date of Filing

25-Feb-1999

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	SACHCHIDANANDA CHAKRABARTI	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, CALCUTTA 700032, INDIA.
2	MIHIR DAS	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, CALCUTTA 700032, INDIA.
3	SYAMAL GHOSH	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, CALCUTTA 700032, INDIA.
4	SHANKAR GHATAK	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, CALCUTTA 700032, INDIA.

PCT International Classification Number

B32B 9/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA