What porcelain dishes are made of. Everything about porcelain: types, classification, painting. Porcelain decoration

Introduction

Porcelain is the main representative of fine ceramics. The characteristic features of porcelain are white with a bluish tint, low porosity and high strength, thermal and chemical resistance and natural decorative effect. Its features are determined by the chemical composition and structure of the shard, which depend on the purpose of the product, the conditions of their operation and the requirements imposed on them.

Porcelain has high mechanical strength, chemical and thermal resistance, electrical insulating properties and is used for the manufacture of high-quality tableware, decorative and sanitary ware, electrical and radio engineering parts, corrosion-resistant devices for chemical technology, low-frequency insulators, etc.

Porcelain is usually obtained by high-temperature firing of a fine mixture of kaolin, feldspar, quartz and plastic clay (such porcelain is called feldspar). The term "porcelain" in the English-language literature is often applied to technical ceramics: zircon, alumina, lithium, boronic and other porcelain, which reflects the high density of the corresponding special ceramic material.

Porcelain is also distinguished depending on the composition of the porcelain mass into soft and hard. Soft porcelain differs from hard porcelain not in hardness, but in that when firing soft porcelain, more liquid phase is formed than when firing hard porcelain, and therefore there is a higher risk of deformation of the workpiece during firing.

Hard porcelain is richer in alumina and poorer in fluxes. To obtain the required transparency and density, it requires a higher firing temperature (up to 1450 ° C). Soft porcelain is more varied in chemical composition. The firing temperature reaches 1300 ° C. Soft porcelain is mainly used for making art products, and solid usually in technology (electrical insulators) and in everyday life (dishes).

One of the types of soft porcelain is bone china, which contains up to 50% bone ash, as well as quartz, kaolin, etc., and which is distinguished by its special whiteness, thinness and translucency.

Porcelain is usually glazed. White, matte, non-glazed porcelain is called biscuit. In the era of Classicism, biscuit was used as inserts in furniture

PRODUCTION PROCESS

Preparation of raw materials

The composition of the ceramic mass and the method of its preparation are determined based on the purpose of the product, its shape and type of raw material. The purpose of the preparation of raw materials is the destruction of the natural structure of materials to the smallest particles in order to obtain a homogeneous mass and accelerate the interaction of particles in the process of porcelain formation. It is carried out mainly by a plastic method, which ensures that a mass uniform in composition is obtained.

Plastic materials (clay, kaolin) are dissolved in water in paddle mixers. The resulting mass in the form of a suspension is passed through a sieve (3600 - 4900 holes per 1 cm2) and an electromagnet to remove large inclusions and ferrous impurities.

Depleted materials and fluids are sorted, free from foreign and harmful impurities. Quartz, feldspar, pegmatite and other components are fired at a temperature of 900-1000 ° C. In this case, quartz undergoes polyform changes, as a result of which it cracks. This, firstly, facilitates grinding, and secondly, it allows you to remove pieces contaminated with ferrous impurities, since during firing quartz with impurities of ferrous compounds acquires a yellow-brown color.

Stony materials, including broken porcelain, are washed, crushed and coarsely ground on runners, and then sieved. Fine grinding is carried out in ball mills with porcelain or uralite balls. To intensify the grinding, a surface-active additive is introduced into the mill - sulfite-alcohol stillage (from 0.5 to 1%), which, filling microcracks, has a sort of wedging effect. Grinding is carried out to a residue of 1-2% on a sieve with 10,000 holes per 1 cm2.

Plastic and lean materials, fluff and porcelain breakage are thoroughly mixed in a propeller-type mixer. The homogeneous mass is passed through a sieve and an electromagnet and dehydrated in special filter presses or vacuum filters. The resulting plastic mass with a moisture content of 23-25% is sent for two weeks to aging in a room with high humidity. During aging, oxidative and microbiological processes, hydrolysis of feldspar and the formation of silicic acid occur, which contributes to loosening of the mass, further destruction of the natural structure of materials and an increase in the plastic properties of the mass. After aging, the mass is processed on mass mills and vacuum presses to remove air inclusions, as well as plasticity and other physical and mechanical properties necessary for the formation of products.

Types of porcelain

Depending on the composition of the porcelain mass and glaze, hard and soft porcelain are distinguished. A certain intermediate form is represented by the so-called bone china.

Hard porcelain contains mainly two starting materials: kaolin and feldspar (most often in combination with white mica; it melts relatively easily). Quartz or sand is added to these basic substances. The properties of porcelain depend on the proportion of two main substances: the more kaolin its mass contains, the more difficult it is to melt and the harder it is. This mixture is ground, kneaded, milled and then dried to the degree of a doughy state capable of taking shape. A plastic mass arises, which can be either cast in molds or grinded on a potter's wheel. Finished items are fired twice: first without glaze at a temperature of 600-800 degrees C, then with glaze - at 1500 0 C. Feldspar or pegmatite is used as fluff. “Sometimes dolomite and lime spar are additionally introduced to enhance translucency. Cover hard china with hard glaze. Thin varieties are covered with a lime-free spar glaze, so the products are matte, milky-creamy. But simpler varieties are covered with a completely transparent lime glaze. Glaze and porcelain are composed of the same substances, only in different proportions. Thanks to this, they are connected and the glaze can no longer be beaten off or peeled off. "

Hard porcelain is distinguished by its strength, strong resistance to heat and acids, impenetrability, transparency, conch-like fracture and, finally, clear bell sound. Invented in Europe in 1708 in Meissen by Johann Friedrich Boettger.

Soft porcelain , also called artistic or frit, consists mainly of mixtures of vitreous substances, the so-called frits, containing sand or flint, saltpeter, sea salt, soda, alum and crushed alabaster. After a certain melting time has elapsed, marl containing gypsum and clay is added to this mass. In principle, this means that we are talking about a fused vitreous substance with an addition of clay. All this mass is ground and filtered, bringing to a plastic state. The molded object is fired at 1100-1500 ° C, making it dry and non-porous. Glaze is mainly made of glass, that is, from a fusible substance, rich in lead oxide and containing, in addition, sand, soda, potash and lime. Already glazed products undergo a secondary firing at 1050-1100 ° C, when the glaze is combined with the shard. Compared to hard, soft porcelain is more transparent, the white color is even more delicate, sometimes almost creamy, but the heat resistance of this porcelain is lower. The fracture is straight, and the unglazed part is granular in the fracture. Most early European porcelain was soft, as exemplified by the beautiful and highly prized Sevres. It was invented in the XVl century in Florence (Medici porcelain).

Bone china represents a well-known compromise between hard and soft porcelain. Its composition was discovered in England and its production began around 1750. In addition to kaolin and feldspar, it contains lime phosphate from burnt bone, which makes it easier to melt. Bone china is fired at 1100-1500оС. So, we are talking essentially about hard porcelain, but one that is softened by mixing the burnt bone.

Its glaze is basically the same as on soft porcelain, but contains, in addition to lead oxide, a certain amount of borax for better connection with the shard. With the appropriate glowing heat, this glaze melts and adheres firmly to the shard. According to its properties, bone china occupies an intermediate position between hard and soft porcelain. It is tougher and harder than soft china and less permeable, but it has a rather soft glaze in common with it. Its color is not as white as that of hard porcelain, but whiter than that of soft porcelain. For the first time bone china was used in 1748 in Bau by Thomas Fry.

From the above, we can conclude; that the main, for the manufacture of porcelain, there are three types, which differ in composition, firing temperature and are used for different types products. Also, for each type, its own glaze is made.

PORCELAIN PRODUCTION TECHNOLOGY

... Porcelain production

The production process for the manufacture of ceramic products consists of several stages:

preparation of raw materials;

preparation of the mass;

product formation, firing;

glazing and decor.

Preparation of raw materials consists in purification of raw materials from impurities, thorough grinding, sieving, drying, etc. Preparation of the mass consists of mixing raw materials in certain proportions and mixing the mixture with water until a homogeneous liquid porcelain mass is obtained. The mass is passed through a sieve, cleaned (electromagnetically) from iron impurities and dehydrated (on filter presses or vacuum presses) to obtain a molding dough.

· Free forming on a potter's wheel;

· Plastic molding by hand impression in the form;

· Plastic molding in a rotating plaster mold using a forming template or roller;

· Forming the vessel by the method of circular molding. Slip casting into plaster molds;

· Production of ceramic products by a combination of several molding methods.

The method of free molding of ceramic products on a potter's wheel consists in the mechanical action of a potter's hands on a clay blank in the form of a plastic dough. First, the master prepares the potter's wheel for work. The first stage is the primary processing of the workpiece. Then, the inner cavity of the product, the edges of the blank, and again the inner cavity are formed. After that, the master pulls the workpiece to the desired height. During all these operations, he rotates the potter's wheel with his foot or a drive mechanism. The process ends with finishing the outer surfaces, trimming the bottom, drying. During drying, the product can be decorated with stucco details, seals, stamped with stamps.

Plastic molding by hand impression is carried out using plaster molds. Forms can be open and detachable; open ones are used for forming flat products; detachable - when making products according to volumetric models of complex shapes.

Plastic molding in a rotating plaster mold using a template or roller occurs as follows. The mold, which opens into two halves, is assembled and installed in the rotating bowl of the machine. A lump of clay is fed into the inner cavity of the mold, calculated for the volume of the product being made. A forming template is lowered into the mold cavity, which evenly distributes the clay mass in the inner side of the mold, after which it is lifted and removed from the mold. Then the mold with the product is removed from the setting machine, dried, opened, the product is taken out and further processing is continued (attachment of parts - spouts, handles, lids and other additional mounts).

Slip casting into gypsum molds is based on the property of gypsum, to absorb moisture, and the ability of clay to transfer from a liquid slip to a state of a plastic dough with decreasing moisture content. Products are formed as follows. The slip is poured into the inner cavity of the gypsum mold, resulting in a redistribution of moisture between the slip, which gives off moisture, and the gypsum mold, which absorbs this moisture. After the redistribution of moisture on the inner working surface of the gypsum mold, a layer of clay mass is formed from the slip, which turns into a state of plastic dough. When the mold has "gained" a given thickness of the clay layer, the slip is poured from the inner cavity of the mold, and the clay layer on the inner surface of the mold remains. This layer of thickened slip is a molded hollow ceramic product - raw. As it dries, the raw material in the form decreases and separates from its walls.

The manufacture of ceramic products by combining several molding methods makes it possible to obtain products of complex shapes. The combination of a plastic molding method in a rotating plaster mold with a metal template or a roller with slip casting and mounting of attachment parts is widespread in the production of teapots, sugar bowls, cups, decanters, bowls and other porcelain and earthenware products consisting of a body and individual parts. After molding, the products are air-dried and fired.

And what is porcelain made of?

PORCELAIN: The composition of which the best stone dishes are made: porcelain clay, kaolin, weathered feldspar with quartz.
V. Dahl
Over a thousand years ago, people in China drank from jade cups. They were very expensive.
After many years of searching and many failures, Chinese potters made a material that surpassed jade in its qualities, turned out to be more accessible and easier to process.
It was porcelain. For a long time it was called "imitation of jade". The "China Secret" was the secret of the raw materials. In the province of Jiangxi, there were huge reserves of "porcelain stone" - a rock consisting of quartz and mica. The porcelain mass was made from briquetted powder of "porcelain stone" (pe-tun-tse) and kaolin, which gave the product whiteness. Kaolin was abundant in the same province. The mass was "aged" for more than a dozen years, so that they acquired plasticity. The glaze was composed of several layers of different transparency, obtaining a special, matte sheen.
Porcelain was used not only for tableware (the imperial court received 31,000 dishes, 16,000 plates with dragons, 18,000 cups every year), but also benches, gazebos, and in 1415 the Nanjing Pagoda was built. Porcelain vessels were in China and musical instruments: tapping a thin stick on their walls gave birth to a melody.
All porcelain can be divided into three main groups - oriental porcelain, European hard porcelain and soft porcelain (semi-porcelain). The main component of Eastern and European hard porcelain is kaolin (non-melting porcelain clay and feldspar). There is more kaolin in European china than in eastern china, and it requires a hotter fire when fired. This gives it transparency, but in such a fire all colors fade, except for blue. Therefore, European porcelain has to be painted over glaze, while oriental porcelain allows you to use a number of paints for underglaze painting.
Hard porcelain, or simply porcelain, is a homogeneous, white, strongly ringing, hard and difficult to melt, with an insignificant thickness, a very transparent mass, in a fracture, greasy, shiny, conchial, fine-grained; hard porcelain consists mainly of kaolin and feldspar mixed with quartz, lime, etc., and is covered with hard glaze.
Soft porcelain consists of not completely melted, glassy, fine-grained mass, with lead, crystal-like, siliceous glaze. The low-melting glaze, which makes it look like Chinese porcelain, allows for thick writing and much softer tones than hard porcelain. English soft porcelain (bone china) contains burnt bone, phosphate salts, kaolin, etc. It occupies a place between stone mass and hard porcelain, resembles white alabaster and is extremely transparent.

Kirill Sysoev

Callous hands do not know boredom!

Content

Many people at home have a cup or statuette made of bone china, but few know what it is and where to buy it. This type of material is distinguished by its thinness, translucency and sophistication. It was designed by the English potter Josiah Spode. Cookware made from this material is often marked Bone chine or Fine bone china. According to its characteristics, it occupies an average value between soft and hard material.

What is bone china

This kind of porcelain means a special kind of hard material with the addition of burnt bone. It is very durable, yet white and transparent. High strength properties are achieved due to the melting of the main ingredients during the firing process. It was created in an effort to recreate the famous Chinese porcelain formula. At the end of the 18th century, bone ash began to be added to the composition of the material, and in the process of development of technology, a basic formula was developed.

The dishes made of this material do not have an eggshell effect, which is achieved due to the fact that the voids between the particles of white clay are filled with bone ash. Thus, bone china is one of the most popular materials, which, thanks to its whiteness and transparency, has won a leading position in sales in the world market. Sets made from it can have a pleasant cream shade.

Composition

Before ordering Chinese bone china, pay attention to the composition. The basic formula for the manufacture of this type of material provides for 25% of kaolin (special white clay) and feldspar with an admixture of quartz, 50% of burnt animal bones. The first firing is carried out at a temperature of 1200-1300 ° C, and the second - 1050-1100 ° C. In this case, the bone ash contains about 85% calcium phosphate.

The bones that are used as part of the porcelain mass must undergo a special treatment, as a result of which they begin to burn out - this is necessary to remove the glue from them and heat up to a temperature of 1000 ° C. Organic matter in this case, they burn out, and the structure of the bones changes to the required state. From the resulting mass using gypsum molds, objects are obtained, on the surface of which, after firing, various patterns are applied.

If necessary, the products are covered with a layer of glaze and sent back to the oven. Flowers and artistic patterns and lines are applied to the product using a decal - a thin film. They also use painting. In general, finished plates, cups, and other utensils are thinner than conventional china bases. Modern technologies provide for the replacement of biological calcium phosphate with mineral. This does not change the quality of the dishes.

Advantages

If you need bone china, it is better to buy it in a specialized online store. Some deliver by mail. Branded items have a number of advantages due to which they become popular with consumers. The material is distinguished by a softer color and special whiteness, which similar materials do not have. The qualities are achieved by adding ground and processed bones to the composition. Many people prefer this type of porcelain for its:

smoothness;
airiness;
translucency;
refinement.

What is the difference between bone china and ordinary

This type of porcelain differs from analogs in that a unique component is added to the composition - ground and processed animal bones. Due to the ingredient finished products becomes softer, and its walls are thinner. In the light, the material begins to shine a little, which gives the sets an airiness and originality, an aristocratic look. Despite all the elegance, fine porcelain has good mechanical strength, making it durable.

How to store

On sale in Moscow, St. Petersburg, you can find a rich assortment of bone-type porcelain products - tea, dining sets, decorative vases with different decor, figurines, figurines and more. All of them have an attractive and original look, different shades and can last for many years due to the unique properties of the mixture. Before ordering a product, read the following tips for caring for it:

do not put the products one on top of another - plates, cups, saucers, but if such a need arises, then be sure to shift each of them with napkins;
arrange kitchen utensils so that they do not touch each other - there should be a distance between them;
do not wash thin-walled porcelain products with hard sponges or hot water;
it is better not to use chemical detergents for washing, otherwise they can ruin the drawing or cause fading of cutlery colors;
products do not tolerate sudden temperature changes, therefore, before brewing a cup of tea or coffee, preheat them - first with warm water, then a little hot, etc.;
move objects made of bone material when cleaning kitchen furniture with paper napkins to prevent the appearance of chips;
wipe the porcelain with a dry cloth, removing dust from cups, saucers, etc. as carefully as possible;
do not store the sets near sources of open flame - they may deform as a result of heating.

Major manufacturers of bone china

The leaders among all manufacturers of products from such porcelain are considered the British, who were the first to master the technique of making material with the addition of bone ash. Japanese manufacturers also have excellent skills and considerable experience in the field of creating thin-walled porcelain: they have changed the established proportion of the bone component in the composition of the porcelain mass. The Japanese have developed a special formula, thanks to which the familiar technology has significantly improved. Famous manufacturers:

Imperial Porcelain Factory (IPP)... It was founded in 1744 by Empress Elizabeth, daughter of Peter the Great. At that time, the factory became the first porcelain factory in Russia and the third in the whole of Europe. In the early years there were manufacturers of small things - mostly snuffboxes for the Empress. Over time, a large forge was built and the factory began to produce larger items. The manufacture was reorganized with the accession of Catherine II. The end of the 18th century was the heyday of Russian porcelain, and the IPZ became one of the leading factories in Europe. As for porcelain with bone ash in the composition, a suitable mass was first developed in Soviet time- in 1968. The first such batch was produced by the IPE. Now the enterprise is the only one in Russia that produces bone porcelain mass and items from it.
Royal doulton... A company from England, which has been specializing in the production of bone material for a long time and has the status of one of the largest manufacturers and suppliers of it. Together with the British factory Wedgwood, it is part of the alliance. Founded in 1815, the headquarters is located in Stoke-on-Trent (Great Britain). Royal Doulton produces porcelain items in a variety of shapes, sizes and uses. The collections of this company are very popular in many countries.
Wedgwood... Another well-known company producing products from bone china mass. She has been supplying it for the English royal court for over 200 years. The foundation of the Wedgwood brand dates back to 1759, when Yeshua Wedgwood rented a manufactory in Burslem. In addition to classic tableware, the company produces avant-garde lines, which include products of non-traditional forms, objects of art.
Spode... Bone china brand from the UK with 200 years of experience. The company offers mugs, plates, sets, made to the highest quality standards. The manufacture has existed since 1770. Josiah Spode (founder) perfected the bone china formula and was the first to supply tableware to the English royal court in the 18th century. In 2009, Spode merged with the Portmeirion Grou, a renowned luxury porcelain company.
Narumi... A Japanese company that was founded in 1911. Its products combine modernity and tradition, West and East, unique beauty and versatility. Since 1965, Narumi has been engaged in the mass production of porcelain. Narumi Bone Pieces are mostly handcrafted. The brand has become a leader in the field of luxury porcelain Bone China.

Choice

Buying an exquisite underglaze porcelain product requires a competent and serious approach, especially if you are going to choose an expensive souvenir self made... It is also important to distinguish a fake. This high-quality creation has a pure translucent white color and gloss with good strength characteristics. Some companies are trying to combine innovative solutions with traditional recipes and designs. Criterias of choice:

Material color... It should have a warm light shade and not be too white.
Transparency... If the product is of high quality, then its walls will transmit light well. Holding the thing in your hands, you can clearly see the outlines of your fingers through it.
Examine the drawing applied to a porcelain item. Often it is applied by hand, so you can see the characteristic strokes, the trace of the brush.
Pay attention to the manufacturer... It is advisable that on the back of the porcelain creation there was a mark of one of the famous brands. If the manufacturer is unfamiliar to you, then postpone the purchase, first study all the information about him.
It is important to make sure the object is smooth., absence of holes, inclusions, bubbles, scratches, chips on the surface and along the edges.

Where can I buy

You can buy products made of bone china mass with a cold white tint at outlets that specialize in the sale of luxury tableware. Look for large stores that have frequent promotions to reduce the cost of goods. Attend outlets on your own: you will have a chance to take a good look at the items and make sure of the authenticity. To order next item from a trusted seller on the Internet. It will be good if you can agree to pay the main payment after checking the item.

Price

The cost of bone china varies greatly depending on the manufacturer and the type of product. Sets, cups and saucers in which are so thin that they can transmit light, are in great demand. From the table you can find out the current prices for some types of bone china sets:

Set name	What is included	Price in rubles
Royal Boné China Gold embroidery for 6 persons	6 cups, 6 saucers
Japonica Grace JDYSQH-5 for 6 persons	6 cups, 6 saucers
Royal Aurel Hoarfrost for 6 persons	6 cups, 6 saucers, kettle
Hankook Chinaware Silver Ribbon for 2 persons	2 cups, 2 saucers
Lenardi series Golden Symphony for 6 persons	6 cups, 6 saucers
Royal Aurel Grace for 6 persons	6 cups, 6 saucers
Lenardi Series Silver Symphony for 6 persons	6 cups, 6 saucers
Lenardi series Meissen bouquet for 6 persons	6 cups, 6 saucers
Japonica Paradise JDFES-9 for 2 persons	2 cups, 2 saucers
Japonica Grace JDYSQH-4 for 6 persons	6 cups, 6 saucers, 1 teapot, 1 milk jug, 1 sugar bowl

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Bone china - what it is: the properties of dishes

Porcelain is a very ancient material, but today it is popular and in demand in many industries around the world.

What is porcelain?

This material is considered one of the varieties of ceramics. Products are made from such raw materials by high-temperature processing of white clay - kaolin, including additional ingredients such as feldspar, quartz, burnt bone. Firing the mass allows you to endow ready product water-repellent properties, attractive color - white or cream. In addition, porcelain becomes non-porous, and the material for tableware and decorative items the characteristic ringing becomes inherent.

Kaolin is a pure clay that forms when feldspar breaks down. Before processing, Chinese stone is crushed to a powdery state, after which the mixture is subject to temperature processing in the range from +1200 to +1500 degrees. As a result of firing, the Chinese stone changes its consistency and fuses to form non-porous glass. Kaolin stands out for its resistance to heat, so it retains its original shape. The porcelain making process is considered complete when these materials are combined into one working mass.

A bit of history

Most sources indicate that China is the birthplace of porcelain. The emergence of this raw material is attributed to the period of the VI-VIII century A.D. NS. For many years, the formula and composition of this material were kept secret, and interesting decorating techniques, including "rice porcelain", were also born there. In Central Asia, porcelain products appeared approximately in the 9th century, after 7 centuries the technology of making unique raw materials became known to Japanese masters, and later porcelain production began in Europe.

The history of the creation of Russian porcelain dates back to the 18th century, but initially such material was similar to faience in its technical specifications... The formation of the production of porcelain products in Tsarist Russia had two directions - at that time private manufactories functioned, and also the production of products from this raw material was established under the leadership of the royal dynasty.

Among the most famous facilities that are still operating, it is worth highlighting Imperial Porcelain Factory, where small items such as tea sets, snuff boxes and buttons for the Empress were originally made. With the advent of Soviet power, private manufactories were nationalized, and many manufacturing technologies were lost.

In the 30s of the XX century, thanks to the efforts of the masters, some of the basics related to the invention of high-quality raw materials were restored, and the artistic aspect of painting porcelain products began to improve.

As for the European trend in the history of porcelain, the first craftsmen to try to create this material were Italians. Also, the British, French and Germans tried to succeed in this matter. However, they did not manage to achieve such a result as the Chinese did immediately.

The first samples of European porcelain were more like glass. A real breakthrough in this direction was made in Germany, where the young alchemist Böttger and physicist Walter von Chirnhaus discovered large deposits of white clay, which radically differed from other fossils in its plasticity.

The workshop for the production of raw materials was opened in 1710, but the material was invented much later, after long and hard work, which in the future was crowned with world recognition of Meissen porcelain.

Advantages and disadvantages

Today, many products are made from porcelain with different purposes. In each case, the composition of the material can change, in the light of which certain features of the raw material come to the fore. In general, the following should be highlighted positive traits porcelain:

the raw material is completely impervious to moisture;
the material has no voids in its composition, which is considered a big plus in terms of the hygiene of porcelain products;
porcelain dishes are resistant to chemicals, in particular to acids;
despite the fact that porcelain products are mostly thin, the material stands out for its resistance to mechanical damage;
souvenir products, as well as sets and other utensils are capable of transmitting light, which gives them a special grace and airiness;
products made from high quality raw materials stand out for their noble color without gray tint;
the surface of porcelain products will be perfectly smooth;
most of the decorative products can be used in everyday life for eating, which makes them versatile.

The material and products from it are not devoid of some disadvantages:

most porcelain products require special approach regarding care and storage;
as a rule, high-quality products are distinguished by their high cost;
tableware and souvenir products do not withstand sudden temperature fluctuations.

Types and their properties

Today, there are several varieties of this raw material, which differ in quality properties, as well as technological nuances related to production.

Solid

This species is also called natural. Modern manufacturers make it using different amounts of the main components - kaolin and Chinese stone. The first ingredient plays a major role in endowing the raw material with such an indicator as strength, but at the same time it is rather unstable to mechanical damage, therefore it beats easily. The hard variety usually has a lot of weight, such porcelain will not be transparent, and its surface may contain microscopic pores.

The material is obtained due to high-temperature heating of the components, as a rule, to obtain raw materials, the mass is heated to an average of 1500 degrees, the firing process takes place in several stages. Initially, hard porcelain will be gray or blue-white, with subsequent processing the shade of the raw material changes to a more noble one. The components of hard porcelain are not distinguished by their high cost.

As practice shows, this variety is significantly inferior in quality to bone china, however, products from a solid type will be many times more affordable.

Soft

The second variety is called the other way around - artificial porcelain. This name is due to the fact that the soft look was first obtained in Europe when trying to repeat the skills of Chinese craftsmen who made hard material. Feature technological process the manufacture of soft porcelain is firing, but when the mass is exposed to not such critical temperatures, in light of which the raw material is not completely sintered, but remains porous. Among the remarkable features, it is worth highlighting the more attractive color of the material, which will be closer to cream.

Another variety is considered bone and cold porcelain ... The first type, in addition to the main components, additionally consists of burnt bone mass, it is durable, stands out for its transparency and whiteness.

Such material also involves the use of a certain technology for firing feldspar mass with a pretreated bone component, from which the adhesive component is removed. It is this porcelain that is called thin, since products made from it are distinguished by their thinness.

Argentine craftsmen were involved in the production of cold porcelain, who used glue, glycerin, oils, and corn starch as ingredients. The mass is similar in consistency to plasticine, solidifies after the end of the mechanical action. Raw materials are very plastic, therefore they are used for the manufacture of fine and filigree products. The material is sold ready-made.

Painting options

Modern manufacturers of porcelain products in practice use several options for painting:

overglaze;
underglaze;
intraglaze.

The essence of overglaze design is to apply coloring compositions to the surface of an object that has been burnt and covered with a special glaze. The substances used differ from other coloring compositions by the presence of a liquid component that can lower the temperature.

Underglaze painting is done before applying the glaze composition. Since in the future such a product will be exposed to temperatures, the color assortment of the substances used in this case is distinguished by a minimal assortment. Most often, chrome or cobalt oxide is used for patterns.

The material with intraglaze painting lends itself to a temperature treatment of + 1200C-1300 degrees. In the course of such exposure, the applied coloring composition eats into the glazed layer, which has a positive effect on the preservation and brightness of the paints even with their subsequent contact with acidic media or alcohols.

In this case, color schemes range from muted colors in gold, pink or gray tones to richly colored ornaments on the products.

Manufacturers overview

Today, the main manufacturers of porcelain products can be distinguished:

"Kuznetsovsky porcelain"- a small enterprise specializing in the manufacture of tableware and souvenirs;
Center for the revival of traditional crafts "Skudelnik"- a company engaged in the manufacture of souvenirs, artistic porcelain, as well as construction and architectural products from ceramics;
Gzhel porcelain factory – large enterprise, which is engaged in the production and sale of hand-painted products;
PC "Dulevo Porcelain"- manufacturer of products for interior decoration, as well as products of folk arts and crafts;
Sagradelos- Spanish factory for the production of ceramics;
Pickman- European manufacturer of porcelain tableware;
english trade marksRoyal Doulton and Wedgwood.

How to distinguish from a fake?

In order not to be mistaken with the choice of porcelain products, you should adhere to the following rules.

Quality ceramics should be thin but durable. Its cost depends on how thin the raw material is. Therefore, in the price of the product, through which you can see how your hands shine through. This applies to tableware, as well as decorative items.
In addition to being transparent, real porcelain also has to "sound" in a certain way. Usually, products are checked for falsification using a wooden stick. The sound when it comes into contact with porcelain should be sonorous and melodic, while the deaf one will indicate that the tested product is a fake.
It is also important to pay attention to what color the material will have. Ideally, products made from quality raw materials will be white or ivory; gray should alert the buyer.
It is worth paying attention to how the product is made. Quality products will be flawlessly smooth everywhere, dents and bumps will indicate the poor quality of the products offered.
The drawing deserves special attention. Even hand-painting should be uniform and accurate, however, it is allowed if brush strokes are visible on the surface.
It is also worth paying attention to the marking of products and brands. Usually their manufacturer applies to reverse side products. It is worth giving preference to well-known brands.

Application features

The purpose of the material is not only the production of tableware and products for interior decoration. Porcelain is used for the production of technical parts because of its low water absorption and hardness. This applies to the hard variety of raw materials. Soft porcelain is mainly used for the production of art products, tableware, etc. Also, raw materials are in demand in dental offices, in particular for the production of dental crowns.

Porcelain acts as a material for the production of washbasins, toilets and sinks, raw materials are in demand in microelectronics, in addition, some types of armor are produced on the basis of porcelain.

We systematize porcelain according to the composition of raw materials. All porcelain can be divided into three main groups - oriental porcelain, European hard porcelain and soft porcelain (semi-porcelain).

Hard porcelain, or simply porcelain, is a homogeneous, white, strongly ringing, hard and difficult to melt, with an insignificant thickness, a very transparent mass, in a fracture, greasy, shiny, conchial, fine-grained; hard porcelain consists mainly of kaolin and feldspar mixed with quartz, lime, etc., and is covered with hard glaze. Thinner varieties have a feldspar glaze, no lime, resulting in a milky matte tone; simpler varieties have a crystal clear lime glaze.

Porcelain fired without glaze is known commercially under the name "b and s c w and t a"; but for the most part porcelain is glazed, painted and covered with gilding over glaze or under glaze. French production is distinguished by outstanding advantages, especially in Limoges, where each factory has its own specialty, in which it achieves incomparable results. In Germany, Meissen takes the first place, then Berlin, as well as Pirkenhammer and Elnbogen in Bohemia.

Weights for porcelain

Porcelain products are distinguished by fine grinding of the initial components of the mass, high firing temperature, whiteness, translucency, lack of open porosity, high strength, thermal and chemical resistance. Porcelain masses consist of fine mixtures of kaolin, quartz, feldspar and other aluminosilicates. The main charm of porcelain is its whiteness and translucency, therefore the purest ceramic raw materials are used for the manufacture of porcelain. To increase the plasticity of the mass, some of the kaolin is sometimes replaced with highly plastic white refractory clay or bentonite. Depending on the composition of the mass and the firing temperature, there are hard porcelain fired at a temperature of 1350-1450 ° C and above and soft porcelain, the firing temperature of which is below 1350 ° C. Compared to soft, hard porcelain contains more kaolin and less feldspar (up to 36% and up to 28% feldspar, respectively). Soft porcelain is divided into feldspar, low-temperature (high-feldspar), frit, bone, etc.

The first firing of hard porcelain is carried out up to a temperature of 850-950 ° C. Bone china is produced from masses containing bone ash, calcium phosphate, feldspar, etc. It is fired first at a temperature of 1230-1250 ° C, then at a glaze melting temperature of 1050-1150 ° C. Frit porcelain contains low-melting alkaline frits fused from quartz sand, soda, potash, saltpeter, gypsum, and other materials. Firing of frit porcelain is carried out at first at a higher temperature (1200-1300 ° C), and at a lower one. Low-temperature porcelain is made from low-sintering masses and covered with a dull white zirconium glaze. The main components for its manufacture are kaolin, bentonite, pegmatite, alumina, dolomite and other materials. The shard is sintered, fired once at a temperature of 1160-1180 ° C, water absorption is up to 0.5%.

Semi-porcelain is characterized by a white or colored dense semi-sintered shard covered with a translucent or colored glaze. In terms of composition and firing temperature, it occupies an intermediate position between porcelain and hard feldspar earthenware. Water absorption is 5-8%. Firing products at a temperature of 1150-1250 ° C. Porcelain items should have a sintered shard covered with a colorless transparent glaze, sometimes a specially painted shard, or specially coated with colored glazes. The whiteness of porcelain is currently regulated by the standard and is 55-68%. Products are made smooth or with a relief, with a smooth or figured edge, decorated with underglaze and overglaze ceramic paints, decals, chandeliers, preparations of precious metals, etc. Porcelain products are made mainly in two ways: casting and molding using a template in plaster molds. Articles made of bone and frit porcelain, due to the absence or small quantity plastic materials in the composition, are made only by casting, sometimes with adhesives. The mechanical strength of soft porcelain is one and a half times less than hard porcelain.

Hard porcelain, depending on the purpose, is divided into 3 groups:
1.Household and artistic (dishes, figurines, vases).
2.Electrotechnical (insulators).
3.Chemical porcelain ( glassware and etc.).

Most harmful impurities porcelain - Fe2O3 and TiO2. To improve the molding properties, along with kaolin, highly plastic white-burning refractory clays and plasticizers (4-5% bentonite) are introduced into the porcelain mass. Feldspar or pegmatite are used as fluxes for the production of porcelain. Sometimes dolomite, lime spar, etc. are additionally introduced to enhance translucency. To ensure high quality of products, raw materials are finely ground, the fineness of which is controlled by a sieve of 10,000 holes / cm2. Due to the very small sintering interval of frit porcelain, in order to prevent deformations, the firing of products is carried out in special clay molds with supports. Defective products after firing often exceed 50%.

Bone china It is distinguished by its high whiteness, translucency and decorative effect, but such porcelain is easily deformed during firing. Separate types of bone unglazed porcelain are called pariana (low-transparent material with a yellowish tint) and carrara (reminiscent of white Carrara marble). Bone china is used to make tea and coffee sets, as well as biscuit sculptures. For the manufacture of tableware, this material is not used, since it is unstable to the action of acids and alkalis.

High feldspar porcelain resembles hard porcelain and is characterized by a lower content of clay matter and a higher content of quartz and feldspar. It is produced according to the scheme of production of hard porcelain, and the temperature of the first firing is 950-1000 ° C, and the second 1250-1300 ° C. It has a lower mechanical strength and heat resistance than porcelain, but it has a higher transparency and great decorative possibilities (lower temperature of watered firing). It is used for the manufacture of expensive sets, sculptures, etc.
In some cases, porcelain masses can be painted with ceramic pigments based on cobalt, chromium, nickel, etc., depending on the maximum firing temperature. Ready-made porcelain masses can be used as a material for the manufacture of decorative items with crystalline and matte glazes, firing them at a temperature of 1100-1200T.

Soft porcelain embraces two completely different varieties, more or less approaching porcelain in color, transparency and glaze, but very sensitive to rapid temperature changes. Before the appearance of hard porcelain in Europe, soft porcelain was used. If you run a knife over soft porcelain, the glaze cracks; in this way it is easiest to distinguish it from hard porcelain, the glaze of which will not suffer in such a case.

French soft porcelain consists of not completely molten, glassy, fine-grained mass, with lead, crystal-like, siliceous glaze. The low-melting glaze, which makes it look like Chinese porcelain, allows for thick writing and much softer tones than hard porcelain. English soft porcelain (bone china) contains burnt bone, phosphate salts, kaolin, etc. It occupies a place between stone mass and hard porcelain, resembles white alabaster and is extremely transparent. For painting, it offers the same advantages as French and German, but is especially favorable for gilding and jewelry with precious stones.

Main component oriental and european solid porcelain is kaolin (non-melting porcelain clay and feldspar). There is more kaolin in European china than in eastern china, and it requires a hotter fire when fired. This gives it transparency, but in such a fire all colors fade, except for blue. Therefore, European porcelain has to be painted over glaze, while oriental porcelain allows you to use a number of paints for underglaze painting.

European semi-porcelain does not contain kaolin and therefore is only suitable for porcelain appearance, and its composition is closer to glass. During firing, it does not require a high temperature, which allows using a larger amount of paints, which, fusing with the glaze, give the painting a special transparency and shine.

If we try to classify products made of baked clay in order of complication of their manufacturing technology, we will get the following scheme: primitive hand molding and fire burning; pottery and kiln firing; majolica; semi-faience; faience; porcelain. These technologies have appeared at different times and in different countries, having, depending on this, significant features. Today, almost all of them exist in modern versions, and in any, even the most primitive technique, using the most uncomplicated technology, a talented ceramist can achieve great success. The Russian language has long and firmly entered the terms denoting products made of clay. So, as they say, let's deal with the terms first.

The most general concept, which includes all products and materials obtained by sintering clays and their mixtures with mineral additives, as well as oxides and other inorganic compounds, is ceramics. Further, if you observe the chronology in the development by people of the properties and capabilities of clay as a material, there are stucco and pottery. I think everyone understands that the pottery is made on a potter's wheel, and the stucco ones are molded by hand. But nevertheless, there is one caveat. Pottery is a term for items made on a potter's wheel without further use of glaze. And earthenware, majolica, and even porcelain can also be made using a potter's wheel, but we do not call them pottery. The main distinguishing feature is that earthenware and majolica are glazed. Moreover, it is very difficult to draw the line and determine how many percent you need to cover the pottery with glaze and paint, so that it turns into majolica.

Some modern masters cover their potter with glaze from the inside, which is why, in their opinion, it does not turn into majolica. The name of this pottery comes from the name of the island of Mallorca, where, under the influence of Moriscos from the city of Malaga (Spain), in the 14th-15th centuries, the production of ceramic products from naturally colored clays, completely covered with a dull tin glaze and painted, flourished. Majolica production spread to Northern Italy, gaining special development in the vicinity of the cities of Faenza and Urbino. I think you guessed that it was the name of the city of Faenza that gave the name to the next kind of pottery - faience. But here I must make a reservation: it is still not completely clear what appeared earlier - majolica or faience - not as names, but as types of ceramics. Indeed, until now, majolica is sometimes called "simple faience", which means that faience is a more general concept that includes majolica.

Today majolica is called ceramic products from naturally colored low-melting clays, the red shard of which is covered with a dull glaze, with water absorption of 10-15 percent. Faience is the name given to ceramic products covered with transparent glaze with water absorption from 9 to 12 percent. The color of earthenware can be different: mainly light tones to white. The composition of earthenware masses can be divided into three groups: clayey ancient faience - made of clay and ground fired flint or quartz; calcareous, or soft, faience (typical medieval) - from clay, fired flint or quartz and marl or chalk; feldspar, or hard, - from clay, flint or quartz and feldspar, first made at the beginning of the 18th century in Germany.

The most ancient earthenware vessels covered with glaze, or, as it is otherwise called, glaze, were made in Egypt. From Egypt, the art of glazing came to Babylonia and Assyria, and from there it penetrated into Persia, where it flourished mainly in the field of building art. Different literary sources give different opinions on the use of glaze by the Greeks and Romans. For example, the German researcher of the history of faience A.N. Cuba believed that the Greeks and Romans knew the technology of using glaze, but their exclusive love for a clean shard limited their use. And when ancient culture collapsed, the art of glazing perished with it for Europe. But in the Middle Ages, faience appears again and again in the East. At the beginning of the XIII century, the Arabs who crossed from Africa after seven years of stubborn struggle took possession of the Iberian Peninsula. And now, together with the Arabs, earthenware production appears in Spain, which will remain at the mercy of Eastern traditions for a long time. Eventually, Spanish-Moorish pottery appears - a kind of bridge between East and West. Then, from Spain, earthenware production penetrated into Italy, where it reached its peak in the middle of the 16th century in the so-called Italian majolica.

In Ancient Rus, glazed ceramics have been known since the 10th century. So, at the end of the 19th century, in the rich pagan mounds near the village of Gnezdovo (near Smolensk), fragments of two plates and mugs of white clay, covered with glaze and decorated with multi-colored painting, were discovered.
The production of majolica, which passed from Italy to other countries of central Europe, later developed into the production of earthenware with a white or cream-colored skull covered with transparent lead glaze. This is how French faience, the famous Dutch Delft faience, German and English faience arose. Even curiosities often contributed to the development of earthenware production in Europe. So in the late 17th - early 18th centuries, wars undermined the economy of France and, in need of funds, Louis XIV forbade the use of gold and silver dishes, which led to the rapid development of the production of ceramics, and in particular faience.

In the 17th century, faience covered with transparent lead glaze was called semi-faience. The prefix "semi" did not contain anything disdainful or indicative of poor quality, it only indicated the technical differences between these faience and "real" faience, covered with an opaque tin glaze. The best results in the use of transparent lead glazes were achieved in Germany by the Hirsch-Vogel family and in France by Bernard Palissy.

The so-called Turkish semi-faience (XVI-XVII centuries) belongs to the group of soft faience, which was made from a mixture of red-burning clay with chalk. Usually this semi-faience was engobed or covered with pewter glaze and decorated with thick pastes using ocher (bolus), which gave the surface of the product some relief.

In Europe, the production of earthenware reached its heights in England in the 17th century, when the English ceramist Josiah Wedgwood (Wedgwood) invented high-quality earthenware masses ("cream", "basalt", "jasper"). His most remarkable work is in Russia. This is a 952-piece dinner service ordered by Catherine II (in England it was called "Russian"). Each piece of this service bears the author's personal stamp - a green frog.

In Russia, the time of birth and rapid development of the production of faience was the 18th century. The first factory known to us was founded in Moscow in 1724 by the merchant of the first guild Afanasy Grebenshchikov. In 1752, the State Faience Factory was opened in St. Petersburg, and then the Imperial Faience Factory, where Dmitry Vinogradov worked. In 1757, Ivan Sukharev's factory, which had previously been engaged in the manufacture of paints, began to work. In the second half of the 18th century, the mass production of numerous factories and workshops near Moscow Gzhel. In August 1809, in the village of Domkino, Tver province, one of the most interesting Russian faience factories arose, which soon took a leading place in the domestic ceramic business - the future Konakovsky (Kuznetsovsky) factory. And in September 1810 A.Ya. Auerbach, who from the very first days carried out a number of measures to strengthen his company.

In 1870, the Auerbach plant was sold to M.S. Kuznetsov - a bright, colorful personality, typical of the period of development of capitalism in Russia. M.S. Kuznetsov added this enterprise to the factories he owned in Dulevo, Vladimir province (founded in 1832) and in Riga (founded in 1843). By this time, Kuznetsov's enterprises were already noticeable in Russia. The former Auerbach plant in the Tver province became one of the enterprises of an extensive Kuznetsov company, which included: a ceramic enterprise in the village of Budy, Kharkov province, a Gardner plant in the village of Verbilki, Dmitrovsky district, a plant in the city of Slavyansk, Chernigov province, a plant in the village of Pesochnaya, Yaroslavl province, faience factory in the village of Pesochnya, Kaluga province. In 1889, the "MS Kuznetsov Partnership for the Production of Porcelain and Earthenware Products" was established with a board in Moscow. In 1918, by decree of the Council of People's Commissars of the RSFSR, among other major industrial enterprises The Kuznetsov factory in the Tver province was nationalized. But only in the 30s the factory started production and young talented artists I. Frykh-Khar, I. Chaikov, I. Efimov, V. Favorsky, V. Filyanskaya, P. Kozhin, S. Lebedeva, M. Kholodnaya came here.

Some faience factories, along with faience, began to produce porcelain products from the middle of the 18th century. Faience differs from porcelain in that the earthenware mass contains much more clay. In "clay" faience, the clay content reached 85 percent, the firing temperature was 950-960 ° C, such faience was covered with colored dull glaze. This faience was characterized by high porosity and low mechanical strength. The limestone faience of the Middle Ages contained, in addition to clay and flint, another 10-35 percent of limestone or chalk; its firing temperature reached 1100-1160 ° С; The shard was porous (19-22% in terms of water absorption) and low strength. Hard, or feldspar, faience has become widespread since the end of the 19th century. The chalk has been partially or completely replaced with feldspar. Solid earthenware was fired twice: first at a higher temperature (1230-1280 ° C) - to obtain a high-quality shard, and secondly - at a lower temperature (1050-1150 ° C) - only to melt the glaze.

In contrast to the European faience that is not translucent in the shard, Persian faience, the production of which has gone through a long period of rise and prosperity (from the 10th to the 17th century), had a well-translucent shard. Persian faience was prepared from a mass rich in quartz with a small addition of glazed clay after firing. Products covered thin layer white engobe and transparent alkaline glaze with luster metallic sheen or opoka lead-tin glaze. The technology of lustrated ceramics was first described in a 12th century treatise by Abu-l-Fazl Khubaysh Tiflisi. If we talk about the shortcomings of earthenware, then first of all it is necessary to say about its porosity, which leads to the absorption of moisture from the air, which leads to some of its swelling (0.016-0.086% of the volume), to the rupture of the glaze and to the appearance of a flake (small cracks glaze), increasing over time. On all old faience products, the glaze is covered with a tseka grid, which is for collectors a peculiar sign of the authenticity of the old origin of old faience or majolica.
Glaze for earthenware is used fritted fusible. The introduction of 3-4 percent chalk, magnesite and dolomite into the mass, as well as an increase in the firing temperature by 20-40 ° C, can eliminate the coke. Usually, earthenware products reach the limit of their increase in volume after two to three years.

At the end of this brief information on earthenware, I will give the composition of the earthenware masses of some factories. Barmin's plant, Moscow, 1876: 3 pounds of Glukhovskoy clay, 1 pounds of 20 pounds of English clay, 6 pounds of sand, 6 pounds of flask; Konakovsky plant, mid-19th century: clay 29 percent, kaolin 32.5 percent, quartz waste 32.5 percent, breakage 6 percent, firing at 1250-1280 ° C. Let's continue our acquaintance with the types of ceramics. Porcelain is the most complex in composition, the most high-temperature for firing and the most difficult material for humans. The distinctive features of porcelain - white color, lack of porosity, translucency, strength, heat resistance and chemical resistance - are determined both by the composition of the raw material and the technology of its processing. Porcelain was invented in China during the Han period (206 BC - 221 AD). There are the following periods in Chinese porcelain production, named after the ruling dynasties: Tang (618 - 907), Song (960 - 1279), Ming (1367 - 1643), Kang-Hsi (1662-1722), Chieng-Lung (1723 - 1795) ) and new - since 1795. Porcelain reached its heyday in the development of form and decoration during the Kang-Hsi period.

Rarely found favorable composition of "porcelain stone" (nan-kan), large reserves of which are located near the original place of porcelain production (Jindezhen city), greatly simplifies the composition and preparation of porcelain mass with the addition of kaolin. Mineralogically, nan-kan is a sericite sandstone of the composition: 75.06 percent silicon oxide, 0.05 percent titanium oxide, 16.01 percent alumina, 0.41 percent iron oxide, 0.28 percent calcium oxide, 0.60 percent magnesium oxide, 1.97 percent sodium oxide, 3.3 percent potassium oxide and other impurities - 2.2 percent. The mass was kept closed in the ground for 100 years, which made it possible to obtain a mass with high molding properties from non-plastic raw materials, which made it possible to manufacture (already in the Song period) the famous "porcelain of eggshell", that is, products with very thin walls. Chinese ceramists of the school of Professor Zhou-Zhen found that grinding a "porcelain stone" in a modern ball mill does not impart to the porcelain mass the plasticity and cohesion that is achieved when this stone is pounded in mortars and cured, as was done in the old days.

Naturally, the high cost of Chinese porcelain imported into Europe in the 15th - 17th centuries (a whole company of soldiers could have been sold for one porcelain vase) caused attempts to be imitated. These are Medici soft porcelain, French fritted porcelain with marly clay and chalk added to glass, réaumur porcelain, etc. In 1708, the Meissen alchemist I.F. Betger succeeded in making a prototype of European porcelain from kaolin, sand and chalk; but already from 1720 the chalk was replaced by feldspar, and real hard porcelain was obtained. The manufacture was strictly classified. In the 18th century, large manufactories developed, and subsequently factories in Meissen itself, famous for its "Saxon" porcelain.

In Russia, the composition of porcelain was independently developed in 1744 by D.I. Vinogradov, who established porcelain production at the Imperial Factory near St. Petersburg (now the Lomonosov Porcelain Factory). The recipe for porcelain in Vinogradov's record is as follows: "Take calcined quartz 768 hours, prepared clay 384 hours, gerbil, alabaster screened out 74 hours." In this mass, quartz plays the role of a weakener, alabaster - the role of flux, clay - the role of a binder plastic additive. The preparation of clay (a kind of white-burning Gzhel gerbil) consisted in its elutriation.

Modern technologists distinguish between two main types of porcelain - hard (with a small amount of flux), fired with watered firing at a temperature of 1380-1460 ° C, and soft (with an increased amount of flux), fired with watered firing and at lower temperatures, but not lower 1200 ° C. The first, solid, firing is the same - at 900-1000 ° C. It is known that Bronyar (Sevres porcelain factory in France) tested masses in the middle of the last century, firing them even at 1500-1550 ° C, using very finely ground pegmatite as a glaze (pegmatite is a light coarse-grained igneous rock, similar in physical properties to granite ).

In addition to the two main types of porcelain, many special types of technical porcelain and porcelain-like materials are currently known. For example, semi-porcelain, or low-temperature porcelain "vitries-chayna", or English bone china, which I. Spode (the second) began to produce in 1759) in the area of Stoke-on-Trent, where most of the English porcelain factories are currently concentrated ... Bone china is distinguished by high decorative qualities, and they depend on the correct preparation of ash from large bones. cattle, which is part of porcelain. Preparation of bones consists of degreasing, steaming and firing.

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