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Porcelain belongs to very ancient materials, however, today it is popular and in demand in many industries around the world.

What is porcelain?

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

Kaolin is a pure clay that is formed when feldspar breaks down. Before processing, the Chinese stone is crushed to a powder state, after which the mixture is subjected to heat treatment in the range from +1200 to +1500 degrees. As a result of firing, Chinese stone changes its consistency, fuses, forming non-porous glass. Kaolin stands out for its resistance to heat, so it retains its original shape. The process of creating porcelain is considered complete after combining these materials into one working mass.

A bit of history

Most sources indicate that China is the birthplace of porcelain. The emergence of this raw material is attributed to the period of the VI-VIII century AD. e. For many years, the formula and composition of this material was kept secret, and interesting decoration techniques were born there, including “rice porcelain”. Porcelain products appeared in Central Asia around the 9th century, after 7 centuries the technology for manufacturing unique raw materials became known to Japanese craftsmen, and later porcelain production began in Europe.

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

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facilities that are still functioning, it is worth highlighting Imperial Porcelain Factory, where small items were originally made, such as tea sets, snuff boxes and buttons for the empress.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

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

As for the European direction in the history of porcelain, the first masters trying to create this material were the Italians. The British, French and Germans also tried to succeed in this matter. However, to achieve such a result as the Chinese, they managed not immediately.

The first samples of European porcelain rather resembled glass. A real breakthrough in this direction was made in Germany, where the young alchemist Bettger and physicist Walter von Tschirnhaus discovered large deposits of white clay, which was fundamentally different from other fossils in its plasticity.

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

Advantages and disadvantages

Today, porcelain is used to make many products with different purposes. In each case, the composition of the material may change, in the light of which certain features of the raw material come to the fore. In general, the following positive qualities of porcelain should be highlighted:

• the raw material is completely impervious to moisture;
• the material does not have voids in its composition, which is considered a big plus in terms of the hygiene of porcelain products;
• porcelain dishes are resistant to chemicals, in particular, to acids;
• despite the fact that porcelain products are mostly thin, the material stands out for its resistance to mechanical damage;
• souvenir products, as well as sets and other utensils, are capable of transmitting light, which gives them a special elegance and airiness;
• products made from high-quality raw materials stand out for their noble color without a gray tint;
• the surface of porcelain products will be perfectly smooth;
• most of the decorative products can be used in everyday life for eating, which makes them versatile.

Not stripped of material and products from it of some disadvantages:

• most porcelain products require a special approach regarding care and storage;
• as a rule, high-quality products stand out for their high cost;
• dishes and souvenirs do not withstand sudden temperature fluctuations.

Types and their properties

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

Solid

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

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

As practice shows, this kind of to a large extent inferior in quality to bone china, however, solid products will be many times more affordable.

Soft

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

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

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

Argentine craftsmen were engaged in obtaining cold porcelain, who used glue, glycerin, oils, and corn starch as ingredients. The mass is similar in consistency to plasticine, hardens after the end of the mechanical action. The raw material is very plastic, therefore it is used for the manufacture of thin and filigree products. The material is sold in finished form.

Painting options

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

• overglaze;
• underglaze;
• intraglaze.

The essence of overglaze design is the application of coloring compositions to the fired and covered with a special glaze surface of the object. The substances used differ from other coloring compositions in the presence of a liquid component, which is able to reduce the temperature.

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

The material with intraglaze painting lends itself to heat treatment, which is + 1200C-1300 degrees. In the course of such exposure, the applied coloring composition is eaten into the glazed layer, which has a positive effect on the safety and brightness of paints even when they subsequently come into contact with acidic environments or alcohols.

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

Manufacturers overview

Today we can distinguish the main manufacturers of porcelain products:

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

How to distinguish from a fake?

In order not to make a mistake with the choice of porcelain products, you should adhere to the following rules.

• High-quality ceramics should be thin, but durable. The cost depends on how thin the raw material is. Therefore, in the price of the product, through which you can see how the hands are translucent. This applies to dishes, as well as decorative items.
• In addition to the fact that real porcelain will be transparent, it must also "sound" in a certain way. Usually products for falsification are checked with a wooden stick. The sound when it comes into contact with porcelain should be sonorous and melodic, while a deaf one will indicate that the product being tested is a fake.
• It is also important to pay attention to what color the material will have. Ideally, products from high-quality raw materials will be white or ivory, gray should alert the buyer.
• It is worth paying attention to how the product is made. High-quality products will turn out to be flawlessly smooth everywhere, dents and bumps will indicate the poor quality of the proposed products.
• Drawing deserves special attention. Even hand painted should be uniform and neat, however, it is allowed if brush strokes are visible on the surface.
• You should also pay attention to the labeling of products and hallmarks. Usually their manufacturer puts on reverse side products. Preference should be given to well-known brands.

Application features

The purpose of the material is not only the production of dishes and products for interior decoration. Porcelain is used to make technical details, because it has a low water absorption and hardness. This applies to the solid variety of raw materials. Soft porcelain is mostly applicable for the production of art products, dishes, etc. Also, raw materials are in demand in dental offices in particular for the production of dental crowns.

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

Visited the enterprise "Art-Modern ceramics" engaged in porcelain products. It is very pleasant at the present time to see such small (and the company employs about 50 people) production with almost manual labor, where the products remember the warmth of the hands that made them. Due to the peculiarities of production (technology, volume), there are no multi-series products, in-line production.

Everything is produced in small batches and is born within the walls of a small building, divided into different rooms - stages of production. Unfortunately, it is difficult to shoot a report and memorize explanations, so I will only talk about those moments that made an impression on me.

1. In addition to traditional dishes, the company has a lot of corporate orders. Police, traffic police, Russian Railways and others. For example, here is a commemorative contraption for the Mil Design Bureau.

2.

3. Order for the police - Uncle Styopa.

4. And this is a vase for Russian Railways. And it's all hand painted. The only thing is that the images to the left and right of the locomotive were made using decals.

5.

6. Various products.

7. Here, and this is the casting of the workpiece. Gypsum mold into which porcelain mortar is poured. The first question was, how are cavities made inside? It turned out that everything is simple. Plaster mold forms only appearance, and inside everything is filled with a solution.
Then the gypsum begins to take water from the porcelain, and the outer layer of the solution hardens. The more the workpiece costs, the thicker the wall is formed.

8. And then the unnecessary solution is poured out (it goes to reuse) and get a thin-walled contraption.

9. Then the blank is brought to mind, polished, burrs removed and prepared for painting.

10. These are blanks for teapots for KB Mil.

11. Complex things are assembled from several parts.

12. Seals.

13. And these are pasted decals before re-annealing. After the oven, the paint from the decal fuses into the glaze and becomes an integral part.

14. Coloring hares.

15. The second discovery for me was that the cobalt paint is black. And only after the stove it turns blue.

16. Painting.

17.

18. And this is preparing hares for 2011, which will be the year of the rabbit.

19. Mega gate valve.

20. Glaze coating.

21. Clone army.

22. Adorable hares.

23. Painting hares.

24. Model and plaster mold.

25. Kilns for roasting.

26. After firing.

27. All ovens except one are electric. But one works on liquefied gas. One such dressing is enough for one firing.

28. Workshop for the production of plaster molds.

29. Box workshop.

30.

31. Small casting workshop.

32.

33. Final fine-tuning.

34.

35. The plaster figurine of Terkin was created in 1939 (I could confuse the date, since the poem was published only in 41, although work on it began just in 39). For a long time she fell into disrepair. The workshop specialists restored the plaster figurine, made the mold and now there is an opportunity to admire the porcelain Terkin.

The term "porcelain" refers to a wide range of ceramic products that are made at high temperatures. Their hallmarks are smooth surface and low porosity. These properties of porcelain are widely demanded to this day. It is difficult to find any industry or National economy wherever it is used.

The most common decorative porcelain, as well as chemical glassware, dental crowns and electrical insulators. Usually white or off-white, for “baking” this wonderful material arrives as an unpresentable piece of ceramics, which will acquire its usual form only after roasting in high-temperature ovens.

Advantages of Chinese services

In this article, we will discuss the properties and types of porcelain. You will understand why this material was so popular all over the world that huge expeditions were equipped to buy it. For a beautiful service, which today you can buy in any store, then you could get killed.

Oddly enough, but the products of Chinese masters with today's ceramics are only relatives, but not direct ones. To be convinced of this, it is enough to recall the basic properties of porcelain that came out of the workshops of the Celestial Empire. The materials are very similar to each other: both modern and ancient porcelain can be glazed or "natural". But simple ceramics are much softer. And you can't make a high-quality service out of it.

Why is this happening?

Such properties of porcelain as strength and heat resistance are the result of high temperatures at which true Chinese ceramics are produced. It is produced at a temperature of 2,650 degrees Fahrenheit (1,454 degrees Celsius). Compare that to 2,200 degrees Fahrenheit (1,204 degrees Celsius) for plain porcelain. Since the second material is of lower quality, it is not used in the chemical industry and other technological branches of science. In addition, it is Chinese porcelain highest quality transparent to light. Rough ceramics cannot give such an effect.

Spy passions

"Hard paste", or true porcelain, first appeared in China in times (618-907). But really high-quality products, in their properties in no way inferior to modern ones, became known to the world only during the Yuan Dynasty (1279-1368). Early Chinese porcelain consisted of kaolin (china clay) and pegmatite, a rough type of granite.

It was unknown to European potters until the import of Chinese equipment during the Middle Ages. Europeans tried to duplicate the properties of porcelain, but did not succeed in this matter. Since they were not able to analyze its chemical composition, the products they produced resembled elegant, fragile and at the same time durable dishes only externally. It turned out like that. Real spy wars unfolded in order to get the secret of true porcelain production, but the Chinese kept their secret more than life.

Why was this material so popular? Reason - excellent physical properties porcelain. It is stronger than ordinary ceramics, has a high thermal conductivity, which makes it possible to brew excellent tea in teapots from it. In addition, due to the glaze, porcelain has an extremely low soiling, staining only under the influence of synthetic pigments. Cups from ancient Chinese sets retain their whiteness after many centuries.

Erzatsy

After mixing glass with tin oxide to make an opaque material, European artisans tried to combine clay and these alternatives became known as "soft paste", or faux porcelain. But two unpleasant circumstances were upsetting: all these materials turned out to be too soft, it was impossible to make really thin, elegant products from them, and the production costs were too high. In a word, the properties of "ersatz-type" porcelain were very far from perfect.

There is evidence that our masters also mastered the art of producing true porcelain, but all the secrets of Russian ceramics were lost during the period of the Tatar-Mongol invasion, when entire cities were burned along with all their inhabitants. The British were also able to achieve a certain breakthrough. They created a "bone" kind of material.

But what are the main properties of which provided him with incredible popularity in old Europe?

History of creation

In 1707, two Germans named Ehrenfried Walther von Chimhaus and Johann Friedrich Bottger discover a more "sane" production method that uses clay and finely ground feldspar. In the 17th century, English artisans learned through experiments that porcelain could be made almost identical to Chinese porcelain by adding finely ground burnt bones to this mixture.

Moreover, it later turned out that the English version makes it possible to produce transparent ceramics at much lower temperatures, which significantly reduced the cost of production. In addition, porcelain from Foggy Albion fought much worse, was much stronger. So it is not surprising that the British soon filled up half of the Old and almost the entire New World with their services.

What are the properties of bone china? Firstly, products made from it are distinguished by high strength with low weight and thin-walled. Secondly, this type of ceramics cannot be used in the chemical industry, since the substances in its composition react with acids and alkalis.

Raw material

As we have already said, the main components of this material are extremely simple: clay, feldspar, minerals with calcium content. Until now, various companies compete with each other, as it was quickly established that the properties of porcelain and earthenware can be radically changed by adding new elements to its composition. Of course, if the experience is successful.

Even though the composition of the clay varies depending on where it is mined, it still turns into glass (which makes the final product smooth) only at extremely high temperatures. But this is true only for those cases when clays are not mixed with materials whose vitrification threshold is lower. Unlike glass, however, clay is thermally stable, meaning it retains its shape even when heated to a high temperature.

So this material is really unique because it combines the low porosity of glass with the stability and relative strength of simple ceramics. Kaolin, a hydroaluminosilicate, has been used as the main type of raw material at all times. (containing aluminum silicate) and flint, a type of hard quartz, are extremely important ingredients in any type of porcelain. They melt during heating, binding the material into a single whole.

Quartz - the "heart" of porcelain

This is a guarantee of strength. The properties of porcelain (and its use) are largely due to this very characteristic: it breaks poorly (when compared with glass), and small distances between particles ensure the impermeability of the material to air, water, and other compounds.

Quartz is an "alloy" of oxygen and silicon, the two most abundant elements in the earth's crust. It has three functional forms: quartz itself (crystals), opal (amorphous variety) and sand (mixed, dirty fraction). In general, quartz has long been used in handicraft production. Porcelain may also contain alumina and steatite, more commonly known as "soapstone".

Manufacturing process

After the raw material is selected and weighed, it goes to production. First, it is cleaned and ground to very fine fractions. After that, all components are mixed in the required proportion, depending both on the production conditions and on the characteristics of the final products. As soon as the latter are formed, they can be sent to the kiln immediately, or they are pre-cleaned and then covered with a layer of glaze.

Of course, crushed glass first acts in its role. And only after that, future vases, cups, toilet bowls and dental crowns are sent to the furnace mouth. Now let's look at each stage separately. After all, the properties of porcelain and its application depend on their success!

Crushing of raw materials

Perhaps this is one of the most important operations, since the quality of the final product depends on the thoroughness of its implementation. Crushing is carried out using huge mechanical drum crushers. On the second pass, the particle size is brought to 0.25 cm. To turn the feedstock into fine dust, special ball crushers are used. These are huge steel cylinders filled with metal balls. When the whole structure rotates, the particles of raw materials turn into a homogeneous mass of extremely fine grinding.

Cleaning and mixing

The mixture is passed through fine filters, and then fed to a special "conveyor", which is an inclined steel sheets. They vibrate, as a result of which the raw materials are not only automatically mixed, but also sorted, since the largest particles are pushed up. If a wetted material supply is required, water is automatically sprayed into the line.

Sometimes filters with powerful magnets are used, since the latter can remove the smallest iron impurities. Last, if it hits finished products, will give it an unwanted red tint. After that, the finished products are sent to the kiln, where they are fired at the temperatures already indicated by us.

On what conditions of production can the properties of products depend?

It should be noted that during the final firing, many processes take place, on which the properties directly depend. Firstly, all carbon organic impurities are burned, excess water is evaporated, various gaseous fractions come out of the thickness of the future product. If at the same time the temperature is not brought to 1100 degrees Celsius, then silicon and other glaze components will not be able to melt, which means they will not form a smooth and chemically neutral layer on the ceramic surface.

In addition, these connections are necessary to reduce the distance between the particles of materials, to more reliably connect them to each other. After the desired density is reached, the product is cooled, as a result of which the glaze “pulls together”, becomes smooth and especially durable.

Results

So why are we describing all this? The thing is that the properties of this material are closely dependent on the features and conditions of its manufacture. For example, strength depends on the percentage of feldspar content in the mass, and the number of pores in porcelain is the smaller, the more feldspar. As the quartz and the residue obtained from the decomposition of the clay substance dissolve in the glass, the skeleton of the porcelain material becomes weaker and the deformations increase. Depending on the fineness of grinding of quartz, composition of the mass, temperature and duration of firing, the composition of the vitreous phase includes from 15 to 40% of all quartz introduced into the mass. The more it is, the porcelain is thinner and "airier".

Properties as dielectrics are characterized mainly by the resistance to passage electric current in the material and on the surface of the insulator. Distinguish between specific volume and specific surface resistance of porcelain.

In addition, it is of great practical importance Chemical properties porcelain. More precisely, their absence. Glazed ceramics with the addition of a large amount of feldspar and quartz are chemically neutral. Do you think why the mortars of pharmacists and chemists are made of this material? It is much stronger than glass, but it does not react.

The current state of affairs

Today, ceramics (and porcelain in particular) is experiencing a rebirth. It turned out that these materials can be used in the production various types microelectronics. The importance of this for modern civilization does not need to be explained. Scientists also found that when certain additives are added, the strength of porcelain increases exponentially. Currently, even promising research is underway in the field of creating new types of armor based on it. So not toilet bowls alone!

Finally, this material is becoming increasingly important in medicine. Various prostheses and magnificent dental crowns - the demand for them is increasing every year. So it will remain relevant for a very long time.

Porcelain production is a fine art, chemistry, magic, it is not for nothing that the material is called “white gold”. There were times when table sets from it were valued more than precious metals, were considered the privilege of crowned persons.

History of appearance

The secret of porcelain mass production has been a secret for a long time. China is considered the birthplace of the material, where it appeared in 620. For almost a thousand years, Chinese craftsmen remained monopolists, carefully guarding the recipe and the secret of making kaolin products.

Meanwhile, European masters experimented to get the optimal formula. As a result, in 1708, two German scientists, Bettger and Tschirnhaus, succeeded in this. They managed to obtain high-quality raw materials for porcelain. Thus began his era in Europe.

In the same year, 1708, the first manufactory was opened in Dresden, producing unglazed cutlery. Two years later, the craftsmen presented the products to the German king - he approved them. And soon German services conquered other countries.

A detailed description of raw materials and technology appeared later, after 20 years. Gradually, production was mastered in France, England, Russia.

Description

In the classic version, this is a translucent material, thin glazed ceramics. Its characteristic features:

• white color with a blue tint;
• high strength - it will not work to scratch the product with a sharp object;
• low porosity;
• resistance to chemical and temperature effects;
• natural beauty.

Composition and preparation of raw materials

For the manufacture of porcelain, a mass is used, which includes:

• 50% kaolin;
• 25% quartz;
• 25% feldspar.

With such proportions, the mixture is white, with the required degree of transparency, plastic. Not every clay is suitable - only certain varieties.

The preparation of raw materials is necessary to destroy the natural hard materials to the state of the smallest granules and obtain a homogeneous mass. To obtain a uniform composition, plastic kaolin is dissolved in water using paddle mixers.

Then the pre-prepared mass (it has the consistency of a suspension) is sieved through industrial sieves. Each sieve has 3500-5000 holes per 1 cm2. They have a built-in electric magnet that cleans the mixture from large metal impurities.

Feldspar and quartz are cleaned of impurities, after which they are fired in special furnaces. The firing temperature is 900-1000 degrees. In progress heat treatment quartz cracks, it is easier to grind and clean it from iron compounds.

Iron removal is a must, because if this is not done, the finished products will have a dirty brown tint.

For the most fine grinding, special additives are added to industrial mills. They are superficial, they do not affect the quality of porcelain products.

When a homogeneous mass is obtained, it is sifted again, then dehydrated in filter presses and sent for aging. The raw mass is aged in damp rooms for two weeks. During this time, it loosens, its plastic properties increase. Then air is removed from the raw material in vacuum presses and sent to form blanks.

Molding

Porcelain production technology is a complex multi-stage process. This largely explains the high cost of products. For molding blanks, molds made of gypsum or PVC are used.

Molding is carried out in a semi-automatic or automatic way. A special roller and a rotating mold are used to roll out a layer of the same thickness.

Things of complex shape, having decorative and artistic value and complex configuration, are made by casting. For blanks, plaster or detachable molds are used.

Drying

When the future cup, vase, teapot, plate are molded, they need to be dried. The initial moisture content of the raw mass is 22-24%, and after drying, the indicator is reduced to 2-4%. This is necessary to obtain durable products, without internal cracks and deformation.

Drying consists of two stages:

1. Preliminary - the blanks are dried in molds to 15-16% moisture, after which they are removed from the molds.
2. Final - the blanks are dried without molds to 2-4% moisture.

Processing is carried out in special dryers, which greatly speeds up the process. Dried kaolin products are cleaned from seams, dirt, dust are removed and sent for firing.

Burning

The first firing is carried out at a temperature of 900 degrees and takes about 12 hours. Then the product is glazed and fired again.

The re-firing temperature is higher, starts from 1000 degrees - the exact figure depends on the type of porcelain, the technique of its manufacture.

Types of porcelain

The material is classified by manufacturing technique as:

• solid;
• soft;
• biscuit;
• bone.

Solid

It contains from 47 to 66% kaolin. Roasting takes place at a temperature of 1400-1600 degrees. Initially, there is less moisture in such raw materials - the workpieces are practically not deformed.

Bone

This type is considered the most durable, while it is valued for its thin, translucent walls. With apparent external fragility, it is more difficult to break it than the classic one.

Half of the composition of bone china is bone meal - hence the name.

Biscuit

Biscuit porcelain has a porous, rough structure that looks like marble. This feature is explained by the fact that the blanks undergo only primary firing at a temperature of 800 to 1000 degrees.

The matte texture looks so impressive that it is usually not covered with glaze. This technique is used to make vases, figurines, and other interior items. Biscuit porcelain dishes are not made.

Soft

The composition of soft raw materials includes less kaolin - 25-40%. At the same time, the amount of feldspar and quartz is increased - 45 and 30%, respectively. The kaolin mass is not so strong, but very plastic.

There are several varieties of soft porcelain:

1. Feldspar. It contains 50% spar and only 30% white clay. The material is dense, heavy, but not durable, so it is much cheaper than analogues. Fired once.
2. High feldspar. It differs from feldspar in a large amount of quartz - 45%. Specific gravity clay - only 15%. Products from it are considered elite, fired at a low temperature.
3. Frit - durable, resistant to thermal effects, chemicals, affordable. Fired at the lowest temperature. In addition to clay, the composition includes alloys of salts and glass. Frit mass is often used for sculpting figurines and other original things.

Soft kaolin mass was preferred by craftsmen Ancient China, and hard - European craftsmen.

painting

There are two types of painting: underglaze and overglaze.

In underglaze painting, paints are first applied to the product, and then the painted layer is covered with glaze. The glaze is transparent, gives an elegant shine to products, protects against microcracks, ultraviolet radiation, alkalis. Such dishes can be washed many times without compromising quality.

The overglaze technique is performed in the reverse order: first, the product is covered with glaze, and paint is already applied to it. The colors are bright, saturated, but eventually fade, fade.

For sets and accessories of mass production, drawings are applied using the decal technique. First, the drawing is printed on special paper, then it is glued onto a cup, tureen, plate and fired. The paper burns, and the colors are imprinted on the surface of the dishes.

Premium-class porcelain products are piece goods, hand-painted by craftsmen, decorated with gold and silver. The cost of work is high, but real works of art are obtained.

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 apparatuses, 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.

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.

Hard porcelain is richer in alumina and poorer in fluxes. To obtain the necessary translucency and density, it requires more high temperature firing (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 bard (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. Basically, that means 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 source materials from impurities, thorough grinding, sifting, 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 inner 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 the plastic molding method 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.