Porcelain is also distinguished depending on the composition of the porcelain mass on soft And solid. Soft porcelain is different solid not by hardness, but by 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 term "porcelain" in English-language literature is often applied to technical ceramics: zircon, aluminous, lithium, boron-calcium etc. porcelain, which reflects the high density of the corresponding special ceramic material.
soft porcelain
Porcelain painting
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 palette of colors of overglaze painting is richer, 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 to 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.
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 argentine).
Gold paints with a lower percentage of gold content (10-12%) are fired at a temperature of 720 to 760 degrees (bone china is fired at a lower temperature than hard - "real" - porcelain). These paints are more decorative, and the products decorated with them cannot be subjected to mechanical stress (wash with abrasives and in a dishwasher.)
Gold, silver chandeliers, polishing polishing and powdered gold and silver (50-90%) are fired at a higher temperature along with paints. The polishing polish and powdered gold after firing have a matte appearance and are painted with an agate pencil (the pattern is applied approximately like a simple pencil on paper, only you cannot make a mistake with shading the pattern, since this cannot be corrected later. The master in this case must be very highly qualified) Combination matt and shiny gold after polishing creates an additional decorative effect on porcelain. Chandeliers and powdered gold paints are more stable on porcelain than 10-12% gloss. However, in the entire history of the creation of porcelain and its technologies, nothing better and cheaper than decorating porcelain with gloss has been invented.
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 (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 the mixture is diluted to the consistency of thick sour cream. For brushstroke painting with a brush, the paint is diluted a little thicker, for pen painting - a little thinner.
It is important that the paint does not spread from the pen or brush. Underglaze paint is diluted on water, sugar with the addition of a small amount of glycerin.
Story
Porcelain was first obtained in 620 in China. The method of its manufacture was kept secret for a long time, and only in 1708 the Saxon experimenters Tschirnhaus and Böttger managed to obtain European porcelain (Meissen).
Attempts to discover the secret of oriental porcelain continued for almost two centuries in Italy, France and England. However, the result was materials that vaguely resembled porcelain and were closer to glass.
Johann Friedrich Böttger (1682-1719) began to conduct 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 François Xavier d "Antrekol (English) Russian, containing the secret of Chinese porcelain production technology, made by him in 1712, but became known to the general public only in 1735.
Understanding 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 fuse more difficult - arose as a result of long systematic experiments based on experience and knowledge of geological, metallurgical and "alchemical-chemical" relationships. It is believed that the white porcelain experiments went hand in hand with the rothes porcelain because only two years later, in 1709 or 1710, white porcelain was more or less ready for production.
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-melting, with a slight thickness, a very transparent mass, in a break, 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. The thinner varieties have a feldspar glaze, without lime, resulting in a milky-matte tone; simpler varieties have a perfectly transparent lime glaze.
Porcelain fired without glaze is commercially known under the name "b and c c c and t a"; but for the most part porcelain is glazed, painted, and gilded over glaze or under glaze. French manufacture is distinguished by outstanding merit, especially in Limoges, where each factory has its own specialty, in which it achieves incomparable results. In Germany, Meissen is first, followed by Berlin, as well as Pirkenhammer and Elnbogen in Bohemia.
Masses for porcelain products
Porcelain products are distinguished by fine grinding of the initial mass components, high firing temperature, whiteness, translucency, absence 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 products. To increase the plasticity of the mass, part 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, hard porcelain is distinguished, 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 to a temperature of 850-950°C. Bone china is made from masses containing bone ash, calcium phosphate, feldspar, etc. It is first fired at a temperature of 1230-1250°C, then at a glaze melting temperature of 1050-1150°C. Frit porcelain contains alkaline fusible frits fused from quartz sand, soda, potash, saltpeter, gypsum, and other materials. Frit porcelain is fired first at a higher temperature (1200-1300°C), and at a lower one. Low-temperature porcelain is made from low-caking masses and covered with white deaf zirconium glaze. The main components for its manufacture are kaolin, bentonite, pegmatite, alumina, dolomite and other materials. The crock is sintered, fired once at a temperature of 1160-1180°C, water absorption up to 0.5%.
Semi-porcelain is characterized by a white or colored dense semi-baked sherd covered with a translucent or colored glaze. In terms of composition and firing temperature, it occupies an intermediate position between porcelain and hard feldspar faience. Water absorption is 5-8%. Firing products at a temperature of 1150-1250°C. Porcelain products must have a sintered shard covered with a colorless transparent glaze, sometimes a specially colored 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 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. Products from bone and frit china, due to the absence or small amount of plastic materials in the composition, are made only by casting, sometimes with adhesive additives. 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. Economic and artistic (dishes, figurines, vases).
2. Electrotechnical (insulators).
3. Chemical porcelain (laboratory glassware, etc.).The most harmful impurities in porcelain are Fe2O3 and TiO2. To improve the molding properties, along with kaolin, highly plastic white-burning refractory clays and plasticizers (4-5% bentonite) are added to the porcelain mass. Feldspar or pegmatite are used as fluxes for the production of porcelain. Sometimes, dolomite, calcareous spar, etc. are additionally added to enhance translucency. To ensure the high quality of products, raw materials are subjected to fine grinding, the fineness of which is controlled by a sieve of 10,000 holes / cm2. Due to the very short sintering interval of frit porcelain, in order to prevent deformations, the products are fired in special clay molds, with coasters. The marriage of products after firing often exceeds 50%.
Bone china it is distinguished by high whiteness, translucence and decorative effect, but such porcelain is easily deformed during firing. Separate types of unglazed bone china are called pariana (opaque 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 distinguished by a lower content of clay matter and a higher content of quartz and feldspar. It is produced according to the scheme for the production of hard porcelain, and the temperature of the first firing is 950-1000°C, and the second is 1250-1300°C. It has less mechanical strength and heat resistance than porcelain, but has greater translucency and greater decorative possibilities (lower poured firing temperature). It is used for the manufacture of expensive sets, sculptures, etc.
Porcelain masses in some cases can be colored with ceramic pigments based on cobalt, chromium, nickel, etc., depending on the maximum firing temperature. Finished 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 changes in temperature. Before hard porcelain appeared in Europe, soft porcelain was used. If you run a knife over soft porcelain, the glaze cracks; in this way it is most easily distinguished from hard porcelain, the glaze of which in such a case will not suffer in the least.
French 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. 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 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.
European semi-porcelain It does not contain kaolin, and therefore it is suitable for porcelain only in appearance, but in its composition it is closer to glass. During firing, it does not require a high temperature, which allows the use of a larger amount of paints, which, fusing with the glaze, give the painting a special transparency and brilliance.
If we try to classify fired clay products in order of increasing complexity of their manufacturing technology, we get the following scheme: manual primitive molding and fire firing; pottery and furnace firing; majolica; semi-faience; faience; porcelain. These technologies appeared at different times and in different countries, depending on this, having 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. Terms denoting products made of clay have long and firmly entered the Russian language. 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 follow the chronology in the development of the properties and capabilities of clay as a material by people, there are stucco and pottery. I think everyone understands that pottery is made on a potter's wheel, and stucco molded by hand. But nevertheless, there is one nuance. Pottery is a term for items made on the potter's wheel without further application of glaze. And faience, and 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 faience and majolica are glazed. Moreover, it is very difficult to draw a line and determine by what percentage it is necessary to cover the pottery with glaze and paint so that it turns into majolica.
Some modern masters cover their pottery from the inside with glaze, which, in their opinion, does not turn into majolica. The name of this pottery comes from the name of the island of Mallorca, where, under the influence of the Moriscos from the city of Malaga (Spain), in the 14th-15th centuries, the production of ceramic products from naturally colored clays, completely covered with dull tin glaze and painted, flourished. Majolica production has spread in Northern Italy, having received 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 type of ceramics - faience. But here I must make a reservation: it has not yet been fully clarified what appeared earlier - majolica or faience - not as names, but as types of ceramics. After all, 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 made of naturally colored fusible clays, the red shard of which is covered with a dull glaze, with a water absorption of 10-15 percent. Faience is called ceramic, covered with transparent glaze products with water absorption from 9 to 12 percent. The color of faience can be different: mostly light tones to white. The composition of faience masses can be divided into three groups: clay ancient faience - from clay and ground fired flint or quartz; calcareous, or soft, faience (typical medieval) - made of clay, burnt 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 clay vessels covered with glaze, or, as it was otherwise called, with 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 assess the use of glaze by the Greeks and Romans differently. For example, the German researcher of the history of faience A.N. Kube believed that the Greeks and Romans knew the technology of using glaze, but their exclusive love for a clean shard limited them in its use. And when ancient culture collapsed, the art of glazing died for Europe along with it. But in the Middle Ages, faience reappears and again in the East. At the beginning of the 13th century, the Arabs who crossed over from Africa, after a seven-year stubborn struggle, took possession of the Iberian Peninsula. And now, together with the Arabs, faience production appears in Spain, which will remain in the grip of oriental traditions for a long time to come. In the end, Spanish-Moorish ceramics appear - a kind of bridge between East and West. Then, from Spain, faience production penetrated into Italy, where in the middle of the 16th century it reached its peak in the so-called Italian majolica.
Glazed pottery has been known in Ancient Rus' since the 10th century. So, at the end of the 19th century, fragments of two plates and mugs of white clay, covered with glaze and decorated with multi-colored paintings, were found in rich pagan burial mounds near the village of Gnezdovo (near Smolensk).
The production of majolica, which passed from Italy to other countries of central Europe, further developed into the production of faience with a skull in white or cream color, covered with a transparent lead glaze. This is how French faiences, the famous Dutch Delft faiences, German and English faiences arose. Even oddities often contributed to the development of faience production in Europe. So at the end of the 17th - beginning of the 18th century, wars undermined the French economy and, in need of funds, Louis XIV forbade the use of gold and silver utensils, which led to the rapid development of the production of ceramics, and in particular faience.In the 17th century, earthenware covered with transparent lead glaze was called semi-faience. The prefix "semi" did not contain anything disparaging or indicating low quality, it only indicated the technical differences between these faiences and "real" faiences covered with opaque tin glaze. The highest 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 tin glaze and decorated with thick pastes using ocher (bolus), which gave the surface of the product some relief.
In Europe, faience production reached its peak in England in the 17th century, when the English ceramist Josiah Wedgwood (Wedgwood) invented high-quality faience masses ("cream", "basalt", "jasper"). His most remarkable work is in Russia. This is a table service of 952 items, made by order of 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 18th century was the time of birth and rapid development of faience production. The first plant 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. Since 1757, the factory of Ivan Sukharev began to work, which was previously engaged in the manufacture of paints. In the second half of the 18th century, the production of numerous factories and workshops in Gzhel near Moscow became mass. 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 Konakovo (Kuznetsovsky) factory. And in September 1810, A.Ya. became the owner of this faience factory. Auerbach, who from the very first days carried out a number of measures to strengthen his enterprise.
In 1870, the Auerbach factory was sold to M.S. Kuznetsov - a bright, colorful personality, typical of the period of development of capitalism in Russia. M.S. Kuznetsov attached this enterprise to the factories he had in Dulevo, Vladimir province (founded in 1832) and in Riga (founded in 1843). By this time, Kuznetsov enterprises were already prominent in Russia. The former Auerbach plant in the Tver province became one of the enterprises of a vast Kuznetsov company, which included: a ceramic enterprise in the village of Budy, Kharkov province, a Gardner factory in the village of Verbilki, Dmitrovsky district, a factory in the city of Slavyansk, Chernigov province, a factory in the village of Pesochnaya, Yaroslavl province, a faience factory in the village of Pesochnya, Kaluga province. In 1889, the M.S. Kuznetsov Association for the Production of Porcelain and Faience Products was established with a board in Moscow. In 1918, by decree of the Council of People's Commissars of the RSFSR, among other large industrial enterprises, the Kuznetsov factory in the Tver province was nationalized. But only in the 1930s the factory started production and young talented artists I. Frikh-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 content of clay reached 85 percent, the firing temperature was 950-960 ° C, such faience was covered with colored deaf 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 limestone or chalk; its firing temperature reached 1100-1160°C; the shard was porous (19-22% in terms of water absorption) and low-strength. Hard, or feldspar, faience became widespread from the end of the 19th century. Chalk has been partially or completely replaced by feldspar. Hard faience 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.
Unlike European faience, which is not translucent in the shard, Persian faience, the production of which went 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 were covered with a thin layer of white engobe and transparent alkaline glaze with a luster metallic sheen or lead-tin glaze. For the first time, the technology of lustred ceramics was described in a treatise of the 12th century by Abul-Fazl Khubaish 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 swelling (0.016-0.086% of the volume), to the rupture of the glaze and to the appearance of a crack (small cracks). glaze), increasing over time. On all ancient faience products, the glaze is covered with a zeca mesh, which for collectors is a kind of sign of the authenticity of the ancient origin of old faience or majolica.
Glaze for faience is used fritted fusible. The introduction of 3-4 percent of chalk, magnesite and dolomite into the mass, as well as an increase in the firing temperature by 20-40 ° C, can eliminate the cake. Usually faience products reach the limit of their volume expansion in two to three years.At the end of this brief information about faience, I will give the composition of the faience masses of some factories. Barmin's factory, Moscow, 1876: 3 poods of Glukhov clay, 1 pood 20 pounds of English clay, 6 poods of sand, 6 poods of flask; Konakovo plant, mid-19th century: clay 29%, kaolin 32.5%, quartz waste 32.5%, 6% cullet, 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 firing and the most difficult material for a person to get. Distinctive features of porcelain - white color, lack of porosity, translucency, strength, heat resistance and chemical resistance - are determined both by the composition of the feedstock and by 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 a new one - from 1795. Porcelain reached its heyday in the development of form and decoration during the Kang-Hsi period.
Rarely encountered favorable composition of "porcelain stone" (nan-kang), large reserves of which are located near the original place of porcelain production (Jindezhen), greatly simplifies the composition and preparation of porcelain mass with the addition of kaolin. Mineralogically, nan-kan is a sericite sandstone with a composition of 75.06 percent silica, 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 aged in a closed state 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 "eggshell porcelain", that is, products with very thin walls. Chinese ceramists of the school of Professor Zhou-Zhen found that the grinding of "porcelain stone" in a modern ball mill does not impart to the porcelain mass the plasticity and coherence that is achieved when this stone is crushed in mortars and aged, as was done in the old days.
Naturally, the high cost of Chinese porcelain imported to Europe in the 15th - 17th centuries (a whole company of soldiers could be given away for one porcelain vase) caused attempts at imitation. Such are Medici soft porcelain, French fritted porcelain with the addition of marl clay and chalk to glass, Réaumur porcelain, etc. In 1708, the Meissen alchemist I.F. Betger managed to make a prototype of European porcelain from kaolin, sand and chalk; but already from 1720 chalk was replaced by feldspar, and real hard porcelain was obtained. The manufacture was strictly classified. In the 18th century, large manufactories developed, and later 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 set up porcelain production at the Imperial Factory near St. Petersburg (now the Porcelain Factory named after M.V. Lomonosov). The recipe for porcelain in Vinogradov's entry is as follows: "Take calcined quartz 768 hours, prepared clay 384 hours, gerbil, sifted alabaster 74 hours." In this mass, quartz plays the role of a leaner, alabaster - the role of flux, clay - the role of a binder plastic additive. The preparation of clay (a kind of Gzhel white-burning gerbil) consisted in elutriation.
Modern technologists distinguish between two main varieties of porcelain - hard (with a small amount of flux), fired during poured firing at a temperature of 1380-1460 ° C, and soft (with an increased amount of flux), fired during poured firing and at lower temperatures, but not lower. 1200°C. The first firing is the same - at 900-1000°C. It is known that Brongniard (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 porcelains and porcelain-like materials are currently known. For example, semi-porcelain, or low-temperature Vitries-China porcelain, or English bone china, which began to be produced by I. Spode (second) in 1759) in the Stoke-on-Trent area, where most of the English porcelain factories are currently concentrated . Bone china has high decorative qualities, and they depend on the correct preparation of the ashes of the bones of cattle, which is part of the porcelain. Bone preparation consists of degreasing, steaming and roasting.
What is porcelain made of?
Ceramics
True pottery is a dark, opaque, vitrified product and, when broken, is always colored, sometimes brown, and often light grey.
The pottery was freely combined with the local clay deposit. The clay itself causes the flux powder to go into a glassy state at temperatures between 1100-1300'C.
Basically, real ceramics has non-standard components, but consists mainly of natural clay. Usually, additions of other components are not included.
Ceramics can be produced from refined clay, which usually imparts a dark yellow color to the ceramic, a flux then adds a vitrification to the product at the required temperature.
Baking utensils
This condition applies freely to products, including tableware and cookware, which can be used in the oven and then placed directly on the table. Both, clay and various glazed bases, are sometimes used in this direction. Ideally, ovenware should be made from a glazed base that has low thermal expansion. However, sometimes cheap, low quality, low-tech clay cookware is produced. Even with ovenware/cookware, care must be taken both for the ovenware itself and to avoid uneven baking, which can cause pressure inside the item and increase the possibility of thermal shock.
The most basic materials used for the production of ceramic products are:
The clay can be cream or white, so a cream shade contains a higher percentage of ball clay, a white shade contains a higher percentage of white clay. The clay base type becomes porous when fired. Absorbs about 6-8% of water and becomes lighter in weight.
The advantage of clay is the possibility of unglazed firing of at least 12 items at a time. In glaze firing, pin levers must be used separately on the utensil; this is the reason for creating the 3-pin brand standard. This also makes it possible to capture the largest surface during firing; the main difference between clay and other bases is that the factory can produce large quantities in spans, making the product very attractively priced to manufacture. Gloss backing is generally not recommended for use in restaurants and hotels, as it deteriorates and has poor impact protection compared to other backings.
vitrified clay
This specification applies to substrates that have a water absorption of less than 0.5%. When such a base is fired, it increases strength and reduces the chance of chipping, extending the life of the cookware. Because, low thermal expansion will give better thermal performance. This product can be recommended for use in restaurants and hotels, as well as for simmering.
Porcelain
Porcelain is a white, translucent glazed product. It is essentially vitrified clay that is combined with white fired clay to develop a white translucent base.
Unlike most porcelains, it is fired under oxidizing conditions, the base becomes vitrified in the first firing, and the glaze is applied and brought to completion separately in the subsequent glaze firing.
Using a manufacturing method, porcelain is often glazed with high quality to allow underglaze decoration.
Bone china
Bone china has an extremely white base, vitrified and translucent. Curved pin marks are not possible on this basis, and therefore, each item must be mounted on individual setup mechanisms and each item placed on a foot. As a result of this, more space is needed in the kiln for firing. Added to this is the cost of the material and bone china becomes one of the most expensive foundations.
Porcelain
The word porcelain is used as a term to include all ceramic ware that is white and translucent. Bone china may, for example, be included in this classification, although it is certainly not porcelain.
Porcelain is a white, translucent glazed product that is usually fired at a lower temperature, resulting in a blue-gray tint to the porcelain.
Porcelain may be glazed or unglazed; unglazed porcelain can be used to make figurines. The manufacturing process for glazed porcelain allows the decor to be applied in firing or in glaze.
A hard porcelain mass, most typical of porcelain tableware, it is first fired at a temperature of 900-1000'C, giving sufficient strength to the base, then the glaze is applied to the base and fired at a temperature of 1400'C to the required one.
The composition of the soft porcelain mass includes more flux and less clay, which allows the glaze and base to be fired together at lower temperatures of 1250-1300’C.
"Beauty that will last a long time" - this is how porcelain connoisseurs characterize it. And, indeed, this material never ages, remaining perfectly smooth and white, carrying its nobility and grace from generation to generation. And the unique properties of porcelain to this day make it indispensable in the manufacture of serving utensils and interior items.
Why do we appreciate and love this white material?
Naturally, for the extraordinary properties of porcelain. These include not only its physical, but also aesthetic qualities. The most basic of them:
- real porcelain is unusually hard and durable. It is difficult to leave the edge of the knife on the surface of the glaze;
- The material has high heat resistance and can withstand high temperatures. It is not afraid of thermal shocks, which allows you to immediately put a hot object under a stream of cold water;
- good porcelain is absolutely impenetrable. This applies to water and various gases. If the vase leaves a wet mark, then it is faience, not porcelain;
- porcelain is hygienic due to its hardness and lack of porosity. The material is resistant to food acids and alkalis, which provides the dishes with a high degree of safety. And, indeed, porcelain and glassware are considered the most environmentally friendly;
- a high degree of plasticity of raw materials allows you to create products of various shapes, decorated with relief patterns of any complexity and openwork "stucco". This quality gives porcelain products additional beauty and value;
- uniform whiteness. White porcelain can be "warm" tones and "cold", it all depends on the composition of the raw material;
- melody. Different types of material sound different, but they all have a pleasant, melodic sound.
The only negative property of porcelain is its fragility. On impact, the object may shatter or get chipped. Although the bone china of some manufacturers does not break and remains intact even when the plate falls on the parquet (wooden).
What is porcelain made from?
Porcelain, what is it? The answer is simple - this is a special type of ceramics. And he began his journey in ancient China, passing various. At first, these were clay cups fired on a fire, then ceramic products made from a more complex composition of clay with the addition of various impurities. With the advent of faience, different temperature regimes of firing began to be practiced, which made it possible to obtain a more perfect material in terms of chemical and heat-resistant qualities. And it's porcelain.
Composition of porcelain
What is porcelain made from? The main components that are always present in this material are kaolin (50%), quartz (25%) and feldspar (25%). The numbers are, of course, arbitrary. Each manufacturer has his own "recipe" for making porcelain. Therefore, porcelain products from different factories have their own distinctive properties in appearance (whiteness, gloss, transparency, sound), as well as different technical characteristics, which is reflected in their application. For example, it is common to make sculptures, figurines, vases from soft porcelain. Hard porcelain is ideal for tableware.
There is a type of porcelain that breaks into small pieces when struck, and there is one that breaks in large pieces. There are porcelain products that have warm shades of whiteness, and there are “cold” colors that fade into light bluish and gray tones. This is influenced by both the composition of the material and the production process itself.
Production technology
If you do not go into the details of the manufacture of porcelain products, then it consists of several stages, each of which has its own specifics and a number of subtleties:
Preparation of raw materials. This process is divided into two parts. First, the creation of a molding mass from which the product itself is molded (stamped). For this, ingredients are selected in certain proportions. Secondly, the manufacture of glaze, which is responsible for the appearance (shine, dullness), providing the chemical and thermal properties of the product.
Many well-known manufacturers of high-quality porcelain pay great attention to the creation of the molding mass. To do this, the ingredients are thoroughly ground with the addition of water and stirred until a homogeneous viscous consistency. To obtain the best result, there is a special equipment that is responsible for the "purity" of the raw materials. In dry form, the components are ground to a state of flour, all foreign particles are excluded by sifting through a special sieve. Metal grains are pulled out by magnets.
The amount of water in this molding composition is also important. Its excess is removed by a press, which also requires technical equipment. For better uniformity, sometimes the molding mass is left in a special “wet” room for “aging”, in which all components are equally saturated with water. Sometimes already molded figures, but not fired, stand for a long time in a special place for the natural “shrinkage” of the material (for example, Hutschenreuther figurines).
Form making. In order to make a product, you need its size and shape. Since during firing the product decreases in size from 15 to 20% (depending on the type of material), therefore the form is prepared in size larger. Only an artist with skill can accurately draw these dimensions, taking into account the volume of the “raw” product and its shrinkage after firing.
From the layout of the drawing, a plaster mold of the product is made, from which a template (a kind of matrix) will then be created, where the molding mass will be poured. Periodically, these templates are replaced with new ones, as their inner surface wears out and ceases to accurately convey the relief of the drawings.
Under the action of a strong centrifugal force, the mixture is evenly distributed in this form and the output is a product that is 15-20% larger than planned. At this stage, some forms of products require individual, manual work. As a rule, these are the items that need to be collected in parts. For example, tea cup (body + handle), sugar bowl (body + handles + lid), teapot (body + spout + handle + lid + handle on lid), etc.
To do this, use a special mixture - slip. With the help of it, the master “glues” the handle to the cup, the spout to the teapot, and so on. The points of contact are well “plastered” with slip, and the seams are “rubbed” with a wet sponge so that the joints are invisible. This is a labor-intensive work that is done only manually and by professional workers. Often this operation is performed by women, as it requires accuracy and special delicacy.
Burning. This procedure is done in two stages. The first firing of the product takes place at a temperature not exceeding 980°C. Objects are reduced in size, as porcelain is "freed" from water. After the first firing, a “biscuit” porcelain is obtained, which is characterized by porosity, roughness and a matte tone. At this stage, there is a large rejection of products, as many do not pass the test for the correct proportions. Some types of porcelain during testing "lose" 20 - 40% of products due to irregular shape.
The next stage of firing takes place at higher temperatures (up to 1500°C). To do this, the product is dipped in a bath with glaze, which gives the product additional strength and the quality characteristic of porcelain - smoothness. This operation is also performed manually. After dipping into the glaze on the object with a wet sponge, the area that will be in contact with the pallet is wiped (from the glaze). This is done so that while being in the kiln for firing, the product does not stick to the surface of the pallet.
If you turn over a porcelain plate (cup), then on the reverse side you can always see a rough place without glaze - often this is the rim of the bottom.
Decoration. Drawing on porcelain products is applied in different ways. It can be an artistic painting made by an artist, which gives the product additional value and individuality. It can be a decal - a special technology that “overlays” a drawing according to the “translator” principle. To create such “translators”, a technology has been developed with the involvement of special paints that can withstand high temperatures during firing. Often paints with precious metals (gold, platinum) are used in decals.
It is worth noting that the drawing can be performed over the glaze and under the glaze. What does this mean for production? If a drawing in the form of a letter or decal is applied under the glaze, then the product is fired again. As a result of high temperature, the pattern is fused into the glaze and becomes one with the product. Such a picture will never be erased or washed. Sometimes the decoration has many different colors and types of ornament, which requires the gradual application of pattern elements and several firings. This multi-stage firing technology is often used in inlays.
The article contains photographs of dishes from a German company
Porcelain in the generally accepted concept is a white material, smooth, shiny, durable, although it can be fragile from impact. Our acquaintance with porcelain, as a rule, begins with dishes and interior items. Although, according to its purpose, it is divided into three groups: economic and artistic, used in dishes and interior items; chemical, from which products for the laboratory are made; electrical used in equipment. And today we will discuss what types of porcelain exist in dishes, the distinctive qualities and features of their appearance.
Porcelain classification
If we talk about porcelain on a larger scale, based on history, then this material can be divided into two categories: European and Oriental.
European porcelain includes hard, semi-soft and soft compositions of the material. And such a variety of types of porcelain is explained by the fact that Europeans had more favorable economic and technological opportunities at the time when they were “looking for” a recipe for this white material. And today, Europeans are ahead of many in the production and methods of decorating hard porcelain. Although we know that the white material itself was invented in ancient China, however, it is very reminiscent of its characteristics.
The Eastern line, of course, has a history of Chinese porcelain, which is still reflected in the forms of products and their decoration. Oriental porcelain technology involves the production without the use of firing at high temperatures, from which the material is soft and semi-soft.
Both types of porcelain - hard and soft, are used in the manufacture of dishes, cutlery and interior items. What are the distinguishing properties of these two materials and what is their difference?
hard porcelain
Hard porcelain can simply be called porcelain. This is the material whose characteristics correspond to the concept of "porcelain". What exactly?
- fine grinding of components, creating material homogeneity;
- firing at high temperatures;
- white color of different shades, from milky-warm to bluish-cold;
- solid structure and high strength. When cutting food with a knife, there is no trace / scratch on the porcelain surface;
- when tapping with a wooden object, a melodic ringing appears;
- with a slight thickness, it has the ability to transmit light, becoming translucent;
- "not afraid" of temperature changes;
- absolutely hygienic.
The biggest disadvantage of the material is brittleness from impact.
The appearance characteristics of porcelain can be different if low and high firing temperatures are applied with glaze applied to the surface. Moreover, depending on the complexity of the pattern, the glaze can be applied to the product up to six times. And the object goes through the same number of firings. Porcelain happens:
- Biscuit- fired without glaze. It has a rough, matte surface, which tends to absorb moisture over time. It is rarely used in this form, sometimes in interior design items (large vases, statues).
- With hard glaze. The product has a smooth, shiny surface. For this, a certain glaze composition is used with an admixture of a high content of quartz and other components.
- With glaze, which includes a large amount of feldspar. Such products have a milky-matte surface.
- With transparent glaze. The simplest recipe, consisting of a large amount of lime and other ingredients.
It should be noted that in the production of hard porcelain there is a thorough quality control at all stages of operations. Defective dishes after firing sometimes exceed the threshold of 20-25%. Therefore, the price of this type of porcelain is always quite high.
soft porcelain
To increase the plasticity of the mass, kaolin is replaced by a high content of feldspar, obtaining soft porcelain. Products from such raw materials are fired at temperatures below 1350°C. They are characterized by: smooth or embossed surface; smooth or curly edge; a variety of decoration methods, both under glaze and over glaze (using ceramic paints, decals, paints with precious metals). Such material is divided into several types:
Feldspar porcelain
In its composition, in addition to plastic white clay and quartz, it has a large amount of feldspar. In the manufacture of dishes, low-temperature firing takes place, which allows the use of different methods of decoration. The paint is applied both under the glaze and over the glaze. The material has a high density, from which the products do not transmit light at all.
High feldspar porcelain
Very similar to hard porcelain, it is distinguished by a lower content of clay, but a large amount of quartz and feldspar. Roasting takes place at lower temperatures. In this regard, it also has more opportunities for decoration. With good ability to transmit light, it has greater strength and heat resistance. Often used in canteens and belongs to the category - elite.
Frit porcelain
The material is considered one of the many types of ceramics. It incorporates a component - a frit, which reduces the melting point. This allows you to fire at low temperatures, respectively, decorate products by any means. Frit porcelain is transparent and light, but during production there are many deformed products (more than 30%), which also affects its price.
Bone china
In its composition it has a large percentage of bone ash obtained from the bones of large, horned animals. Differs in increased whiteness (milky and "warm" tones), perfectly translucent. The firing technology allows the surface to be varied and colorfully decorated. True, in the manufacture of the shape of products, they are often deformed from high temperatures, which cannot but affect the price.
It is believed that some types of bone china are not too resistant to acids and alkalis, so they are more used in tea and coffee sets than in dining rooms. By the way, English porcelain is often bone, while being soft. Sometimes the material is used as "biscuit" (without glaze) in the manufacture of sculptures and large vases.
And if we return to the classification of porcelain in the categories: Eastern and European, then in the latter (European) kaolin there is always more, and it is fired in a kiln at high temperatures. This allows you to have a more transparent material, but decoration restrictions.
Since most paints “burn out” at high temperatures, European manufacturers often use decal technology for this purpose - paper “translators” with drawings made with special paints, including those containing precious metals.
Oriental manufacturers apply special paints under the glaze. This allows the use of a richer palette of colors, since a low firing temperature is used.
Manufacturers of porcelain tableware
If we talk about companies that produce real porcelain, then, of course, these are European brands with centuries-old histories. All of them make different types of porcelain, but some work only with hard material.
I would like to note the French town of Limoges, as it is distinguished by its special whiteness and hardness. Company Haviland, located in the area, produces high quality products and is famous for its classic designs. The decoration of products of this brand is often inlaid with precious metals, which is why porcelain is called "presidential" or "royal".
The Germans are well known for Meissen porcelain. Distinguished by special quality Royal Porcelain Manufactory Berlin. Factory Rosenthal has different styles. In the Czech Republic - a porcelain manufactory Bohemia. – herend(Herend) is known not only for the quality of porcelain, but also for its unusually artistic paintings, graceful shapes and colorful palette of colors.
Kirill Sysoev
Calloused hands do not know boredom!
Content
Many people have a cup or figurine made of bone china at home, but few people know what it is and where to buy it. This type of material is characterized by thin-walled, translucent and sophistication. It was designed by the English ceramic master Josiah Spoud. Dishes made from this material are often labeled Bone chine or Fine bone china. According to its characteristics, it occupies an average value between soft and hard material.
What is bone china
Under this type of porcelain is meant a special kind of hard material with the addition of burnt bone. It is very strong, but at the same time white and transparent. High strength indicators are achieved due to the melting of the main ingredients during the firing process. It was created in the course of attempts to recreate the formula for making the famous Chinese porcelain. At the end of the 18th century, bone ash began to be added to the composition of the material, and in the process of developing technology, a basic formula was developed.
The dishes made from such material do not have the effect of an eggshell, 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, due to its whiteness and transparency, has won a leading position in sales in the world market. Services from it can have a pleasant cream shade.
Compound
Before ordering Chinese bone china, pay attention to the composition. The basic formula for the manufacture of this type of material provides for 25% kaolin (special white clay) and feldspar mixed with quartz, 50% burnt animal bones. The first firing is carried out at a temperature of 1200-1300 °C, and the second at 1050-1100 °C. The composition of bone ash in this case includes about 85% calcium phosphate.
The bones that are used as part of the porcelain mass are necessarily subjected to special treatment, as a result of which they begin to burn out - this is necessary in order to remove the glue from them and heat them up to a temperature of 1000 ° C. At the same time, organic substances 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, the thickness of the finished plates, cups and other kitchen utensils is less than the usual porcelain base. Modern technologies provide for the replacement of biological calcium phosphate with mineral one. The quality of the dishes does not change.
Advantages
If you need bone china, it is better to buy it in a specialized online store. Some do mail delivery. Branded items have a number of advantages, due to which they gain popularity among consumers. The material has a softer color and a special whiteness, which is not the case with similar materials. Quality is achieved by adding ground and processed bones to the composition. Many 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 analogues in that a unique component is added to the composition - ground and processed animal bones. Due to the ingredient, the finished product becomes softer, and its walls become thinner. In the light, the material begins to shine a little, which gives the sets 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 - these are tea sets, dinner sets, decorative vases with various decors, 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 products, please read the following care tips:
- do not put products one on top of the other - 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 products made of thin-walled porcelain with hard washcloths, hot water;
- for washing it is better not to use chemical detergents, otherwise they can cause damage to the pattern or cause the colors of cutlery to fade;
- products do not tolerate sudden temperature changes, so before brewing a cup of tea or coffee, preheat them - first with warm water, then a little hotter, etc .;
- move the bone material when cleaning kitchen furniture with paper towels to prevent chipping;
- wipe porcelain with a dry cloth, removing dust from cups, saucers, etc. as carefully as possible;
- do not store sets near open flames - as a result of heating, they may be deformed.
Major manufacturers of bone china
The leaders among all manufacturers of products from such porcelain are 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 changed the established proportion of the bone component in the composition of the porcelain mass. The Japanese came up with a special formula, thanks to which the usual technology has been noticeably improved. Known Manufacturers:
- Imperial Porcelain Factory (IPZ). It was founded in 1744 by Empress Elizabeth, the daughter of Peter the Great. At that time, the plant became the first porcelain enterprise in Russia and the third in all of Europe. In the early years, small things were produced there - mostly snuff boxes for the Empress. Over time, a large forge was built and the factory began to produce larger items. The manufactory was reorganized with the accession of Catherine II. The end of the 18th century was the heyday of Russian porcelain, and IPM became one of the leading factories in Europe. As for porcelain with bone ash in its composition, a suitable mass was first developed in Soviet times - in 1968. The first such batch was released by IFZ. Now the enterprise is the only one in Russia that produces bone china mass and objects 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 its largest manufacturers and suppliers. Together with the British factory Wedgwood, it is part of an alliance. Founded in 1815, headquartered in Stoke-on-Trent (UK). Royal Doulton produces porcelain objects of various shapes, sizes and purposes. The collections of this company are very popular in many countries.
- wedgwood. Another well-known company that produces products from bone china mass. She has been supplying it to the English royal court for over 200 years. The foundation of the Wedgwood brand dates back to 1759, when Joshua Wedgwood rented a manufactory in Burslem. In addition to classical tableware, the company produces avant-garde lines, which include products of non-traditional shape, art objects.
- Spode. A brand of bone china tableware from the UK with 200 years of experience. The company offers mugs, plates, sets made to the highest quality standards. The manufactory has existed since 1770. Josiah Spoud (founder) improved 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 Portmeirion Grou, a well-known 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 began to mass-produce porcelain. Narumi bone china products are mostly handcrafted. The brand has become a leader in the field of high-end porcelain Bone China.
Choice
Buying an elegant porcelain product with underglaze painting requires a competent and serious approach, especially if you are going to choose an expensive handmade souvenir. In addition, it is important to distinguish a fake. This quality creation has a pure translucent white color and gloss with good strength characteristics. Some companies try to combine innovative solutions with traditional recipes and designs. Criterias of choice:
- Material color. It should have a warm, light tone and not be too white.
- Transparency. If the products are of high quality, then its walls will transmit light well. Holding the thing in your hands, you will clearly see the outlines of your fingers through it.
- Study the drawing applied to a porcelain object. Often it is applied by hand, so you can notice the characteristic strokes, the trace of the brush.
- Pay attention to the manufacturer. It is desirable that on the back of a porcelain creation there is a marking of one of the well-known brands. If the manufacturer is unfamiliar to you, then postpone the purchase, first study all the information about it.
- It is important to make sure the object is smooth, the absence of holes, inclusions, bubbles, scratches, chips on the surface and along the edges.
Where can I buy
You can buy products from bone china mass with a cold white tint at retail outlets specializing in the sale of elite tableware. Look for large stores that often hold promotions, reducing the cost of goods. Visit the outlets yourself: you will have a chance to take a good look at the items and verify the authenticity. You can order the following product from a trusted seller via the Internet. It will be good if you can agree that you will make the main payment after you check the goods.
Price
The cost of bone china varies greatly depending on the manufacturer and type of product. Services, 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 services:
Set name
What is included
Price in rubles
Royal Bone China Golden embroidery for 6 persons
6 cups, 6 saucers
Japonica Grazia JDYSQH-5 for 6 persons
6 cups, 6 saucers
Royal Aurel Hoarfrost for 6 persons
6 cups, 6 saucers, teapot
Hankook Chinaware Silver Ribbon for 2 persons
2 cups, 2 saucers
Lenardi series Golden Symphony for 6 persons
6 cups, 6 saucers
Royal Aurel Grazia 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 Grazia JDYSQH-4 for 6 persons
6 cups, 6 saucers, 1 teapot, 1 milk jug, 1 sugar bowl
Video
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Bone china - what is it: properties of dishes
