What is porcelain made from? What is porcelain

Tuesday, May 03, 2011 13:10 + to quote pad

Porcelain (Turkish farfur, fagfur, from Persian fagfur) is the most noble ceramics. Porcelain tableware is a white durable tableware characterized by amazing lightness and transparency. Porcelain dishes can be distinguished from products made from other types of ceramics by a clear, long ringing sound that it makes when struck.

Varieties and production technology

Basically, porcelain is made from kaolin, clay, quartz and feldspar. Some terminology:

Plavni in ceramic masses they play the role of emaciating additives. During firing, the fluxes contribute to the formation of a low-melting melt, reduce the firing temperature of products, and increase the density of the crock. Feldspar, pegmatite, nepheline syenite, perlite, chalk, dolomite, talc and other materials are used as fluxes in the masses of fine-ceramic products. The action of smoothers in mass is not the same.
Feldspars are a universal flux in the technology of fine ceramics and in the production of glazes. The earth's crust consists of more than 50% of feldspar rocks, but deposits of feldspars suitable for the ceramic industry are very limited and mostly exhausted. They are aluminosilicates of alkali and alkaline earth metals. Pegmatites, granites, perlites can also be used in production.

Kaolin- white clay, which is formed during the weathering of feldspars. It contains the mineral koalinite, and is widely used in industry.

Quartz- another of the most common minerals in the earth's crust, a rock-forming mineral of most igneous and metamorphic rocks. Included in other minerals in the form of mixtures and silicates. In total, the mass fraction of quartz in the earth's crust is more than 60%.

Usually, two firing of porcelain products is carried out: the first for “scrap”, the second for “watered”. The first “scrap” firing aims to sinter the product and provide it with a certain porosity and strength sufficient for glazing with an aqueous suspension. The second firing is necessary for melting the glaze on the surface of the product and for its interaction with the material of the shard.

To improve the molding properties of raw materials, the porcelain mass used to make the famous Chinese “eggshell” porcelain, i.e. products with very thin walls, kept closed in the ground for 100 years. Nowadays, clay can be subjected to flying, especially if it is of low plasticity. To do this, the excavated clay in the form of small pieces is laid out on the ground in beds, which are periodically watered with water, and shoveled. In this state, for several years, the clay is exposed to water, sun, frost and significantly improves its properties. For the manufacture of fine pottery, clay is elutriated in water from impurities, coarse fractions are separated and, after partial dehydration, they rot in cellars for several months.

Freshly precipitated barium sulfate BaSO4 is used as a reference for assessing the whiteness of porcelain. Whiteness is characterized by the intensity of light scattering, which is recorded by a photometer.

The term "porcelain" in the English literature is often applied to technical ceramics: zircon, alumina, lithium, calcium boron 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 the fact that when firing soft porcelain, more liquid phase is formed than when firing hard porcelain, and therefore the risk of deformation of the workpiece during firing is higher.

Solid- with small additions of flux (feldspar) and therefore fired at a relatively high temperature (1380 ... 1460 ° C). The mass of classic hard porcelain consists of 25% quartz, 25% feldspar and 50% kaolin and clay.

Soft– with a high content of fluxes, fired at a temperature of 1200...1280°C. In addition to feldspar, marble, dolomite, magnesite, burnt bone or phosphorite are used as fluxes. With an increase in the content of fluxes, the amount of the vitreous phase increases and therefore the translucency of porcelain improves, but strength and heat resistance decrease. Clay imparts plasticity to the porcelain mass (necessary for molding products), but reduces the whiteness of porcelain.

Soft porcelain is used mainly for the manufacture of art products, and hard porcelain is usually used in technology (electrical insulators) and in everyday life (dishes).

Porcelain products are very diverse in their chemical composition, properties and purpose. Some of the most famous types of porcelain and their characteristic features are:

Biscuit porcelain- matte, without glaze. There is an opinion that it is called biscuit because of the double firing. The prefixes "bis" and "bi" in many languages mean two. In the production of porcelain, the firing is first carried out, which is called waste firing, and then the firing during glazing follows. Biscuit porcelain is also fired twice, but the second time without glaze. At present, the technology for the production of biscuit porcelain may not include a second firing. In the era of Classicism, biscuits were used as inserts in furniture products.

Porcelain bone- soft porcelain, an indispensable part of which is the ash of the bones of cattle, consisting mainly of calcium phosphate. Nowadays, it is sometimes replaced by natural calcium phosphates. Products made of bone china are characterized by high whiteness, translucency and decorative effect. Experts believe that bone china began to be produced by J. Spod in 1759 in the vicinity of Stoke-on-Tret (England). In our country, high-quality bone china products are produced by the Porcelain Factory. M.V. Lomonosov in St. Petersburg.

Fritted porcelain- well translucent soft porcelain, produced in France since 1738. It contains 30 ... 50% kaolin, 25 ... 35% quartz, 25 ... 35% alkali-rich glass frit. Frits are composite additives to the porcelain mass, which ensure the formation of a vitreous phase, and, consequently, determine the translucency of porcelain. The composition of frits includes: sand, soda, saltpeter, gypsum, table salt and crushed lead glass.

A special place in the classification of porcelain occupies Chinese porcelain. The history of porcelain and the history of China are inextricably linked. In ancient times, jade was mainly used to make dishes in China. But it was too expensive material. The result of a long search by Chinese craftsmen to replace jade is porcelain, the material is more accessible and easier to process. Jade remained a sacred stone in China, and porcelain conquered the Chinese rulers almost immediately.

Of all Chinese porcelain, white is especially distinguished. The secret of its unique fragility and at the same time strength lies in the raw materials from which it is made. Jiangxi province proved to be rich in so-called porcelain stone, a rock composed of quartz and mica. By converting all the components into powder and adding kaolin, a mass was obtained that was stored for many years so that it acquired the necessary plasticity. A special matte sheen was achieved by applying glaze in several layers, of different transparency.

Chinese porcelain is famous for its extraordinary thinness and weightlessness, the walls of the cups are so fragile that they resemble eggshells. Gaining popularity at home, first in the highest circles, and then among the entire population, Chinese ceramics even before our era. began to be exported first to India, Japan and Africa; and only in the XVI century to Europe.

decoration

Colorful decor.

Porcelain is painted in two ways: underglaze painting and overglaze painting.

At underglaze When painting porcelain, paints are applied to unglazed porcelain. Then the porcelain product is covered with transparent glaze and fired at a high temperature of up to 1350 degrees.

Palette of colors overglaze the paintings are richer, the overglaze painting is applied on glazed linen (a professional term for unpainted white porcelain) and then fired in a muffle furnace at a temperature of 780-850 degrees.

During firing, the paint is fused into the glaze, leaving behind a thin layer of glaze. Paints after a good firing are shiny (except for special matt paints used only for decorative purposes), do not have any roughness and subsequently better withstand the mechanical and chemical effects of acidic foods and alcohol.

Professional overglaze painting is carried out on gum turpentine and turpentine oil. Paints are pre-soaked on the palette for a day or more. After work, they are thoroughly rubbed with the addition of turpentine oil. Turpentine in jars should be dry, slightly greasy and greasy (turpentine gradually changes from one state to another). The oil should also be more fluid and thicker. For work, a piece of soaked paint is taken, oil, turpentine are added - and diluted to the consistency of thick sour cream. For stroke painting, the paint is diluted with a brush a little thicker, for pen painting - a little thinner. Underglaze paint is diluted on water, sugar with the addition of a small amount of glycerin.

Among the paints for painting porcelain, a group of paints prepared using noble metals stands out. The most common paints using gold, platinum and silver paint (or Argentina).

Gold paints with a low percentage of gold content are more decorative, and the products decorated with them cannot be subjected to mechanical stress (wash with abrasives and in a dishwasher).

Relief decor.

This type of decoration of porcelain tableware is embedded directly into the material of the object itself by engraving, perforation or by means of relief-like elevations. Porcelain dishes are either cast in molds together with the relief, or the relief or plastic parts of the decor (flowers, buds, leaves, figurines as handles, etc.) are molded separately and then glued on.

History

The composition of hard porcelain was invented by the Chinese around the 6th century, but this production secret was kept in strict confidence. Chinese porcelain reached a high degree of perfection in the 15th and 16th centuries, and in the 16th century, thanks to Portuguese navigators, a large number of Chinese products came to Europe.

Around 1500, the Japanese mastered the production of porcelain. In the 17th and 18th centuries, the Dutch contributed to the acquaintance with Japanese products in Europe, taking them with them along the way from the harbor of Arita in the province of Hizen. After the name of the main harbor where the goods were loaded, this porcelain was called "Imari". The shard of Japanese porcelain is inferior in quality to Chinese, but its decoration is much richer and more varied. In addition to the paints used by the Chinese, the Japanese decorated porcelain with gold.

From time to time getting to Europe starting from the 13th century, Chinese porcelain was inserted into a frame by European jewelers and, along with other precious items, was stored in church, monastery and noble treasuries.

In the second half of the 15th century, the first attempts to imitate porcelain were made in Italy. In 1575, by the will of the Grand Duke of Tuscany, Francesco I di Medici, a soft porcelain manufactory was established in the famous Florentine gardens of Boboli. The so-called Medici porcelain in its properties occupied a middle position between hard and soft porcelain. The manufactory operated until the first quarter of the 17th century inclusive.

In the history of porcelain production, Medici porcelain is only an episode. It was followed by other attempts - in England (Dr. Dwight and Francis Place, both in the second half of the 17th century) and in France (Rouen, Saint-Cloud). This ongoing search was stimulated by the import of Far Eastern porcelain, which increased from the beginning of the 17th century. Until the beginning of the 18th century, all attempts remained unsuccessful - the result was materials that vaguely resembled porcelain and were closer to glass.

For example, Johann Friedrich Böttger (1682-1719) carried out experiments on the creation of porcelain, which in 1707/1708 led to the creation of "rothes Porcelain" (red porcelain) - fine ceramics, jasper porcelain.

However, real porcelain had yet to be discovered. Chemistry as a science in its modern sense did not yet exist. Neither in China or Japan, nor in Europe, raw materials for the production of ceramics could yet be determined in terms of chemical composition. The same was true for the technology used. The process of porcelain production is carefully documented in the travel notes of missionaries and merchants, but the technological processes used could not be deduced from these reports. Known, for example, are the notes of the Jesuit priest Francois Xavier d "Entrekol, containing the secret of Chinese porcelain production technology, made by him in 1712, but which became known to the general public only in 1735.

Letter from François Xavier d'Entrecol on Chinese porcelain production technology, 1712, published by Duhald in 1735.

The understanding of the basic principle underlying the porcelain production process, namely the need to fire a mixture of different types of soil - those that fuse easily and those that are more difficult to fuse - arose as a result of long systematic experiments based on experience and knowledge of geological, metallurgical and "alchemical-chemical" relationships. It is believed that Böttger's experiments with white porcelain went hand in hand with the experiments with "rothes Porcelain", since only two years later, in 1709 or 1710, white porcelain was already more or less ready for manufacture.

It should be noted that Chinese porcelain, from a modern point of view, is soft porcelain, since it contains significantly less kaolin than hard European porcelain, it is also fired at a lower temperature and is less durable.

Together with Böttger, experts and scientists of various specialties worked on the creation of hard European porcelain. European hard porcelain (pate dure) was a completely new product in the field of ceramics.

At the end of December 1707, a successful experimental firing of white porcelain was carried out. The first laboratory notes on porcelain mixtures suitable for use date back to January 15, 1708. On April 24, 1708, an order was given to establish a porcelain manufactory in Dresden. The first pieces of porcelain fired in July 1708 were unglazed. By March 1709, Böttger had solved this problem, but he did not present glazed porcelain samples to the king until 1710.

In 1710, at the Easter fair in Leipzig, marketable "jasper porcelain" dishes were presented, as well as samples of glazed and unglazed white porcelain.

History in Russia.

Attempts to organize the production of porcelain or faience in Russia began under Peter I, a great connoisseur of it. On the instructions of Peter I, Russian foreign agent Yuri Kologrivy tried to find out the secret of porcelain production in Meissen, but failed. Despite this, in 1724, the Russian merchant Grebenshchikov founded a faience factory in Moscow at his own expense, where experiments were carried out on the manufacture of porcelain, but they were not properly developed.

The method of development of science and art, which seemed to be proven in Russia, also failed - the invitation of foreign specialists.
There was only one way, the most difficult and long, but reliable: to organize a search for systematic scientific and technological work, which as a result was supposed to lead to the development of a technology for the production of porcelain. For this, a person was needed who had considerable training, possessing sufficient technical initiative and ingenuity. Such was Dmitry Ivanovich Vinogradov, a native of the city of Suzdal.

In 1736 D.I. Vinogradov with his comrades - M.V. Lomonosov and R. Reiser - at the suggestion of the St. Petersburg Academy of Sciences and by imperial decree was sent “to the German lands to study, among other sciences and arts, especially the most important chemistry and metallurgy, to this matter, as far as mining or manuscript art.
D.I. Vinogradov studied mainly in Saxony, where there were then “the most glorious manuscript and smelting factories in the entire German state” and where the most skillful teachers and masters of this craft worked at that time. He stayed abroad until 1744 and returned to Russia with certificates and certificates of awarding him the title of “bergmeister”, which at that time enjoyed great prestige.

Vinogradov was faced with the task of independently resolving all issues related to the creation of a new production. On the basis of physical and chemical ideas about porcelain, he had to develop the composition of the porcelain mass, technological methods and methods for making the mass of real porcelain. Including - the development of glazes, as well as recipes and technologies for the manufacture of ceramic paints of different colors for painting on porcelain.

More than a thousand different experiments were performed by Vinogradov during his work at, as it was then called, the “porcelain factory”.

In the works of Vinogradov on the organization of porcelain production in Russia, his search for a “recipe” for porcelain mass is of considerable interest. These works refer mainly to 1746-1750, when he intensively searched for the optimal composition of the mixture, improved the recipe, conducting technological research on the use of clays from various deposits, changing the firing mode, etc. The earliest of all discovered information on the composition of the porcelain mass is dated January 30, 1746. Probably, since that time, Vinogradov began systematic experimental work to find the optimal composition of Russian porcelain and continued it for 12 years, until his death, i.e. until August 1758

From 1747, Vinogradov began to manufacture trial items from his experimental masses, as can be judged from individual exhibits stored in museums and bearing his brand and date of manufacture (1749 and later). In 1752, the first stage of Vinogradov's work on creating the recipe for the first Russian porcelain and organizing the technological process of its production was completed.

It should be noted that when compiling the recipe, Vinogradov tried to encrypt it as much as possible. He did not use Russian, but used Italian, Latin, Hebrew, and German words, also using their abbreviations. This is due to the fact that he was given special instructions about the need to classify the work as far as possible.

Vinogradov's success in making porcelain at the porcelain factory at that time was already so significant that on March 19, 1753, an announcement appeared in the St.

In addition to formulating porcelain masses and studying clays from various deposits, Vinogradov developed glaze compositions, technological methods and instructions for washing clays at deposits, conducted tests of various types of fuel for firing porcelain, drafted and built furnaces and furnaces, invented formulas for porcelain paints and solved many related issues. It can be said that he had to develop the entire technological process of porcelain production himself and, moreover, at the same time prepare his assistants, successors and employees of various qualifications and profiles.

As a result of “diligent work” (as he himself assessed his work), original Russian porcelain was created. The factory achieved great success both in terms of the quality of porcelain and the variety of products made from it. In conclusion, it should be noted that M.V. Lomonosov also took a considerable part in the creation of original porcelain in Russia, although his share in this matter was incomparably less than D.I. Vinogradova. Which, however, did not prevent later to name the Imperial Plant in the name of Lomonosov, and not Vinogradov.

Marking of porcelain products

Marking, as a way of indicating that a product belongs to a particular production, began to be used in Europe soon after the creation of large ceramic manufactories. But long before that, for example, Oriental (Japanese and Chinese) stamps were reproduced on the Delft faience of the 17th century. By the way, the largest European porcelain factories - Meissen and Vienna - started with the same brands.

The original stamps were introduced for the first time in Europe at the Meissen manufactory in 1723-24. Following this, other factories began to label their products. The stamps, as a rule, were underglaze blue and were placed at the bottom of the product. For a long time, the presence or absence of a mark was at the discretion of the porcelain manufacturers themselves, and only in the last third of the 18th century in the main manufacturing countries (France, Germany, Austria) did marking become mandatory, moreover, the marks had to be registered with the relevant state services.

With the increase in the number of porcelain production in Europe and the recognition of obvious leadership, and, consequently, the greatest value of products from Sevres, Meissen, Vienna and some other manufactories, such a function of marking as protection against imitation and forgery began to come to the fore. For this purpose, for example, in the 19th century, Sevres, Vienna and Berlin introduced the practice of double marking: one mark - usually blue underglaze - was placed during the manufacture of the product, the second - most often red - during its overglaze decoration.

An example of early Ming dynasty porcelain markings

If we talk about the content of brands, then with all their diversity, the following main elements can be distinguished: the names of factories or cities (localities) where they are located; surnames, initials or monograms of owners or their high patrons; heraldic motifs - crowns, emblems or parts of emblems; figures of animals, birds, fish; flowers or other plants; ships, anchors, other marine motifs; castles and various buildings; religious or mythological motifs; various emblems and symbols; geometric figures.

If the product is not marked, then it is necessary to determine it by the method of execution, the shape, the nature of the shard, the color of the glaze and the style of decor. Porcelain and earthenware labels are collected in special reference books and catalogs.

P.S. According to historians, a porcelain cup with a handle - the one that we fill with fragrant tea every day - appeared not so long ago. This truly important event took place around 1730 in Vienna, when some inventive and enterprising porcelain maker came up with the idea of equipping the Chinese gaiwan (bowl) with a side handle, and this design became more convenient for Europeans - after all, before that, they had been drinking for many years coffee from metal cups with a handle, and water, beer or milk from mugs.

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 crock, which depend on the purpose of the product, the conditions of their operation and the requirements for them.

Porcelain has high mechanical strength, chemical and thermal resistance, electrical insulating properties and is used for the manufacture of high-quality tableware, artistic, decorative and sanitary ware, electrical and radio engineering parts, corrosion-resistant chemical technology devices, 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 literature is often applied to technical ceramics: zircon, alumina, lithium, calcium boron and other porcelain, which reflects the high density of the corresponding special ceramic material.

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

One of the types of soft porcelain is bone china, which includes 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, unglazed porcelain is called biscuit. In the era of Classicism, biscuits were used as inserts in furniture products.

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 provides a uniform composition of the mass.

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 ferruginous impurities.

Weakening materials and fluxes are sorted, freed 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, makes it easier to grind, and secondly, it makes it possible to remove pieces contaminated with ferruginous impurities, since during firing, quartz with impurities of ferruginous compounds acquires a yellow-brown color.

Stony materials, including porcelain batt, are washed, subjected to crushing and coarse grinding on runners, and then sieved. Fine grinding is carried out in ball mills with porcelain or uralite balls. To intensify grinding, a surface-active additive is introduced into the mill - sulfite-alcohol stillage (from 0.5 to 1%), which, filling microcracks, has a kind 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 emaciated materials, fluxes and porcelain batt are thoroughly mixed in a propeller-type mixer. A 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 for 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 the 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 grinders 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. Some intermediate type 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; 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 extent of a pasty state capable of taking shape. A plastic mass appears, which can either be cast in molds or turned on a potter's wheel. Finished objects are fired twice: first without glaze at a temperature of 600-800 degrees C, then with glaze - at 1500 0 C. Feldspar or pegmatite are used as fluxes. Cover hard porcelain with hard glaze. Thin varieties are covered with lime-free spar glaze, so the products are matte, milky-cream in color. But simpler varieties are covered with a completely transparent lime glaze. Glaze and porcelain mass consist 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 characterized by strength, strong resistance to heat and acids, impermeability, transparency, conchoidal fracture and, finally, a clear bell sound. Invented in Europe, in 1708 in Meissen by Johann Friedrich Bötger.

soft porcelain , also called art 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, 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, becoming dry and non-porous. The glaze is predominantly made of glass, that is, of a fusible substance rich in lead oxide and containing, in addition, sand, soda, potash and lime. Already glazed products are subjected to 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. The initial European porcelain was mostly soft, which is exemplified by the fine and highly valued products of the 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 there around 1750. In addition to kaolin and feldspar, it contains lime phosphate from burnt bone, which makes smelting easier. Bone china is fired at 1100-1500°C. So, we are talking essentially about hard porcelain, but one that is made softer by mixing 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 appropriate incandescent heat, this glaze melts and is firmly connected to the shard. According to its properties, bone china occupies an intermediate position between hard and soft porcelain. It is harder and harder than soft porcelain and less permeable, but it has a rather soft glaze in common. Its color is not as white as that of hard porcelain, but whiter than that of soft porcelain. Bone china was first used in 1748 at Bow by Thomas Fry.

From the above, we can conclude; that the main ones for the manufacture of porcelain, there are three types that differ in composition, firing temperature and are used for different types of 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;

mass preparation;

product formation, firing;

glazing and decor.

The preparation of raw materials consists in cleaning the raw materials from impurities, thorough grinding, sieving, drying, etc. The preparation of the mass consists of mixing the 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 (with an electromagnet) from iron impurities and dehydrated (on filter presses or vacuum presses) to obtain a forming dough.

free molding on a potter's wheel;

plastic molding by hand imprint in the mold;

plastic molding in a rotating plaster mold using a molding template or roller;

· Formation of the vessel by the method of circular molding. Molding by slip casting in plaster molds;

production of ceramic products by a combination of several molding methods.

The method of free molding of ceramic products on the potter's wheel consists in the mechanical action of the potter's hands on the clay blank in the form of plastic dough. First, the master prepares the potter's wheel for work. The first stage is the primary processing of the workpiece. Then the internal cavity of the product, the edges of the workpiece, and again the internal 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 with a drive mechanism. The process ends with finishing the outer surfaces, trimming the bottom, and drying. During drying, the product can be decorated with stucco details, seals, stamped moldings.

Plastic molding by hand imprint is carried out using plaster molds. Forms can be open and detachable; open ones are used for molding flat products; detachable - in the development of products on three-dimensional models of complex shapes.

Plastic molding in a rotating plaster mold using a template or roller is as follows. The form, which opens into two halves, is installed in the assembled form in the rotating bowl of the machine. A lump of clay is fed into the inner cavity of the mold, calculated on the volume of the manufactured product. 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 form with the product is removed from the setting machine, dried, opened, the product is removed and further processing is continued (attachment of parts - spouts, handles, covers and other additional mounts).

Molding by the method of slip casting into plaster molds is based on the property of gypsum to absorb moisture, and the ability of clay to transfer from a liquid slip to a plastic dough state when the humidity decreases. Products are formed as follows. The slurry is poured into the internal cavity of the gypsum mold, as a result of which moisture is redistributed between the slurry, which releases moisture, and the gypsum mold, which absorbs this moisture. After redistribution of moisture on the inner working surface of the gypsum mold, a layer of clay mass is formed from the slip, turning into a state of plastic dough. When the form has "gained" the specified thickness of the layer of clay, the slip is poured out of the inner cavity of the mold, and the layer of clay on the inner surface of the mold remains. This layer of thickened slurry is a molded hollow pottery raw material. As it dries, the raw material in the form, decreasing, separates from its walls.

The manufacture of ceramic products by a combination of several molding methods makes it possible to obtain products of complex shape. The combination of plastic molding in a rotating plaster mold with a metal template or roller with slip casting and mounting of attachments 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 dried in air and fired.

What to bring from St. Petersburg - crumpets, smelt? Let's say a piece of the curb is still possible (they are sold, so you don't even have to pick it out as a keepsake), but best of all - a product of the Imperial Porcelain Factory. Perhaps every real Petersburger has a cup with the famous cobalt mesh at home. Or a figurine or something special.
Not so long ago, I was able to visit the Imperial Porcelain Factory and see how famous products are created and, of course, that very recognizable cobalt mesh.

Reference: The plant was founded in 1744 (20 years earlier than the Hermitage!) by decree of Empress Elizabeth.
The works of the Imperial Porcelain Factory are included in the treasury of world porcelain and are represented in the collections of the best museums in the world.

3
This is how the Cobalt mesh looks like before firing it is black:

4
This year, the plant celebrates the 70th anniversary of its creation and the 65th anniversary of the launch of its brand name - the Cobalt Net service.
And at the world exhibition in Brussels, the service received a gold medal for the pattern and shape “Tulip”.

5
The author of the service is the artist Anna Yatskevich, she also came up with the official logo of the Lomonosov Leningrad Porcelain Factory - LFZ. Petersburger, born in 1904, Anna Yatskevich remained in Leningrad throughout the blockade, worked, in 1944 - on the occasion of the 200th anniversary of the Porcelain Factory - she was awarded the Order of the Red Star.

6
Anna Yatskevich decided to try cobalt pencils when painting - they have a cobalt core instead of graphite. At first, cobalt stripes alternated with stripes made in red paint.

7
There are many theories about the origin of this traditional decor, but even experts do not know the exact answer.
Perhaps it was inspired by Elizaveta Petrovna's "Own Service" or a Viennese service with a so-called trellis net stored in the factory museum. Or memories of the cross beams of the besieged searchlights bursting into the sky and the cross-sealed windows of the besieged city.

10
Then the products are sent to the oven and the mesh turns blue:

13
The artist has been working on such a dish for about two weeks:

14
Porcelain is usually obtained by high-temperature firing of a coarse mixture of kaolin, quartz, feldspar and plastic clay. But each porcelain is unique and no one discloses its exact recipe.

16
Porcelain is divided into soft and hard. Soft porcelain differs from hard porcelain not in hardness, but in the fact that when firing soft porcelain, more liquid phase is formed than when firing hard porcelain, and therefore the risk of deformation of the workpiece during firing is higher.
The hardest porcelain is bone china.
Bone china is particularly refined, thin-walled and translucent.
Porcelain is usually covered with icing, and uncovered is called a biscuit.
They all look different

17
This is a biscuit (appetizing such names for porcelain are biscuit, icing)

18
Waste production:

19
Liquid porcelain mass, slip, is poured into a plaster mold:

20
Complex products are made from several parts and fastened with a thicker porcelain mass:

21
Like this:

22
Details:

23
Defective figurines also look cool, and you want to take them away (it’s still a marriage, right?), but employees are forbidden to take something away, then it’s all used as raw materials for new products

24
The plaster mold is assembled from two parts, so that later it can be disassembled and the product removed.

25
After some time, the figure is removed:

26
Figurines based on Shemyakin's sketches:

27
And this inscription, as Igor said, must be broadcast in the registry office:

28
Part molds:

31
A copy from the series "Peoples of the Russian Empire":

34
And this is frosting. Before lowering the product into it, it is necessary to mix until a homogeneous state:

36
And then the product is dipped there, just like that, without gloves:

39
Even containers with paints with the famous decor:

41
Porcelain is painted in two ways: underglaze painting and overglaze painting.

When painting underglaze porcelain, paints are applied to unglazed porcelain.
Then the porcelain product is covered with transparent glaze and fired at a high temperature of up to 1350 degrees.
The cobalt mesh is made in this way.

42
The palette of colors of overglaze painting is richer, overglaze painting is applied over glazed linen (a professional term for unpainted white porcelain) and then fired in a muffle furnace at a temperature of 780 to 850 degrees.

43
During firing, the paint is fused into the glaze, leaving behind a thin layer of glaze. Paints after a good firing shine (except for special matte paints used only for decorative purposes), do not have any roughness

55
The red paint will then be removed and the porcelain will remain white in these areas:

58
Kilns are used for firing, which reach 30 meters in length.
Maybe that's what I'd like to see. And in general, while we were walking through the territory of the plant, I noticed photographs from the production on the walls, they looked very picturesque and authentic, and I was looking forward to taking something like that now too.
But it turned out that these photos were taken at a "big" production. The territory of the plant is 5 hectares, everything is occupied by workshops, but there is also a small building where all phases of production are collected in a small area, so that it is convenient to show and conduct tours. That's where we were.

59
On the ground floor there is a shop of the plant, everyone can come there and buy something.
Riddle: how much do you think such a figurine costs?

60
Series with the Hedgehog in the fog:

61
And with the Little Prince, sold at Bukvoed, but here the assortment is better:

62
Petersburg souvenirs:

Taken from mitrofanova_m to the Imperial Porcelain Factory

If you have a production or service that you want to tell our readers about, write to me - Aslan ( [email protected] ) and we will make the best report, which will be seen not only by the readers of the community, but also by the site http://ikaketosdelano.ru

Subscribe also to our groups in facebook, vkontakte,classmates and in google+plus, where the most interesting things from the community will be posted, plus materials that are not here and a video about how things work in our world.

Click on the icon and subscribe!

(better known in St. Petersburg, in Russia, and in the world as the Leningrad Porcelain Factory) was founded back in 1744. The period of its real heyday and all-Russian popularity fell on the years of Soviet power: numerous figurines and utensils of the LFZ became an indispensable part of urban life. The plant produces two million products per year. These are 4 thousand items: services, sculpture, vases, decorative dishes and interior items. The Village went to the illustrious enterprise and found out whether the clay for porcelain from the Donbass is supplied smoothly, whether the "Cobalt Net" is connected with the blockade, and why the percentage of defects in the creation of Kazimir Malevich's set is 70%.

Casting porcelain

To get one finished cup, you need to perform up to 80 technological operations. Porcelain mass is made from fine mixtures of kaolin (white clay), quartz, feldspar and other aluminosilicates and includes up to 40 different additives. The clay from which the porcelain mass is made is from the Donbass, but, despite everything, they assure at the plant, its supplies are uninterrupted.

Hollow products are made by manual or machine casting. Liquid porcelain mass (slip) is poured into plaster molds. Then the form is opened, and a still fragile product is removed from it, which is subject to mandrel and subsequent drying.

Minimalist sculpture is made from "soft" porcelain, fired at temperatures up to 1,280 degrees. It contains the same components, only with a higher content of feldspar.

35 years ago, for the first time in Russia, the plant developed a technology that made it possible to produce products from thin-walled bone china - increased whiteness, thinness and translucency. Calcium phosphates, the ash of cattle bones, were introduced into the composition of the mass, which is why porcelain is called bone.

Photo

Dmitry Tsyrenshchikov

Firing and painting

The products of the plant are decorated with overglaze and underglaze painting in various ways - both manually and mechanized. Underglaze paints are applied to a raw shard; they are more durable, as they are protected by glaze from above, but are limited in palette. The most popular dark blue cobalt. Overglaze paints fired at lower temperatures (720-860 degrees) have a much more extensive color palette. When fired, many ceramic paints change their color, which provides additional artistic possibilities when painting porcelain.

When decorating, a decal is used - a decal printed with ceramic paints on gummed paper and coated with a special varnish on top. When an already decorated product is fired, the film burns out, and the paints are sintered with the glaze, and a pattern remains on the surface of the porcelain.

In Russia and even in the world, the plant is primarily known for its highly artistic painting. A number of products are decorated with natural gold with engraving. Many sets, vases and almost all animalistic sculpture are decorated with underglaze paints. In addition, a combination of rich underglaze cobalt with bright overglaze colors and gold is often used.

Of the unique technologies, cobalt coating and underglaze landscape painting, introduced at the IPM back in the late 19th century, have also been preserved.

"Cobalt Net"

The painting "Cobalt Net" is so popular that it is applied to 100 products, even to horseradish. For several years now, there has been a debate about whether there is a blockade motif in this painting, made by the factory artist Anna Yatskevich in 1944, or not. There is a version that the grid symbolizes a paper tape, which was used to block windows, and gold bugs - searchlights. According to another version, the grid symbolizes cracks in the ice of the besieged Neva, and the golden bugs symbolize the rays of the sun.

There is also a version that the “Cobalt Net” has nothing to do with the blockade and that Yatskevich simply redid the painting of the 19th century for the “Own” service in her own way: instead of a pink net, she made it blue, instead of flowers, golden bugs. Every day, several letters come to the plant with the requirement to "lay out all the ins and outs of the cobalt mesh." The answer to the question of which version is correct is very simple: no one knows and will never know what was in the artist’s head when she painted the “Cobalt Net”: Yatskevich died in 1952 and no one thought to ask her this question during her lifetime .

The Cobalt Mesh service includes six cups, six saucers, a teapot and a sugar bowl. It costs 32 thousand rubles. In 2015, the service went up by 15%, like the rest of the plant's products, because the paints used to paint the products are German.

Individual orders, busts and fight

For the past few weeks, the factory has been discussing a lady who brought a dog (a Saluki breed) to the factory and ordered her sculpture: “The dog is not eternal, but porcelain is eternal.” The artist made a sketch of the dog. There is a lot of work ahead. The artist molds a dog out of plasticine. According to the plasticine figurine, he will make a plaster mold. Porcelain is poured into a plaster mold. The porcelain dog will be dried and sent to the oven. Glaze will be applied to the burned dog. Glaze is matte (products in this technique are called biscuits) and glossy. The dog will be covered with matte glaze.

One of the most "marriage" products at the factory is Kazimir Malevich's set: a teapot and two Kazimir Malevich's "Kazimir and Una" half cups. Malevich was a guest artist at the plant for a total of about eight years. The defect rate of this set is 70%, while the average defect rate for the plant is up to 20%. Half-cups "Kazimir and Una" cost 52,000 rubles and, due to difficulties with their production, are made only to order.

There is a “Boy” room at the plant - marriage is stored there. Marriage is broken with a hammer and then the porcelain mass is used again. It is forbidden to enter the “Fight” room for everyone, except for a specially trained person with a hammer.

Among the political forms at the plant, there are still a bust of Lenin and a bust of Kirov, there is also a meter-long vase from 1936 with the image of Stalin. Such products were placed in their offices by bosses in the Soviet era. The vase with Stalin is made in the agitation porcelain style. Also one of the prominent examples of agitation porcelain is the “Red and White” chess. The red figures on the board are the smiling peasants. And the whites are pawns in chains and depraved women.

Painters

The plant has a catalog with the works of the most famous artists who collaborated with the plant. But there is no catalog of all the paintings and forms made over the 272 years of the plant's existence: there are more than 15 thousand of them, and no one has managed to systematize them yet. This year, the plant's collection has been replenished with two new forms and 15 new paintings.

The plant employs 20 artists and more than 100 painters. Artists create something new, and painters copy what has already been created. To become a painter, it is enough to have an art education and practice at a factory. To become an artist, one must graduate from the Stieglitz Academy of Art and Industry (department of glass and ceramics). The decision on the choice of artists is made by the chief artist of the plant. Now the main artist is Nelya Petrova. Most of all, by the way, she loves natural paintings.

What is porcelain made from?

PORCELAIN: The composition from which the best stoneware is made: china clay, kaolin, weathered feldspar with quartz.
V.Dal
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". "Chinese secret" was the secret of raw materials. In the province of Jiangxi, there were huge reserves of "porcelain stone" - a rock consisting of quartz and mica. 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 made up of several layers of different transparency, obtaining a special, matte sheen.
Not only dishes were made of porcelain (the imperial court received 31,000 dishes every year, 16,000 plates with dragons, 18,000 cups), but also benches, gazebos, and in 1415 they built the Nanking Pagoda. Porcelain vessels were also musical instruments in China: tapping with a thin stick on their walls gave rise 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 Oriental and European hard porcelain is kaolin (non-melting china clay and feldspar). European porcelain has more kaolin than Eastern porcelain and requires a hotter fire when fired. This gives him transparency, but in such a fire all colors burn out, except for blue. Therefore, European porcelain has to be painted on top of the glaze, while Oriental porcelain allows the use of a number of colors for underglaze painting.
Hard porcelain, or simply porcelain, is a homogeneous, white, strongly ringing, hard and difficult-melting, with a slight thickness, a very transparent mass, in a break it is fatty-shiny, conchoidal, fine-grained; hard porcelain consists mainly of kaolin and feldspar, with an admixture of quartz, lime, etc., and is covered with a hard glaze.
Soft porcelain consists of an incompletely molten, vitreous, fine-grained mass, with a lead, crystal-like, siliceous glaze. The fusible glaze, which makes it similar in appearance to Chinese porcelain, allows for thick writing and much more delicate tones than hard porcelain. The composition of English soft porcelain (bone china) includes burnt bone, phosphate salts, kaolin, etc. It occupies a place between the stone mass and hard porcelain, resembles white alabaster and is extremely transparent.