Cosmetic clay: cheap and cheerful. A unique natural remedy for face, hair and body. Clay types properties and applications

Details Created 08/09/2011 21:57 Updated 05/24/2012 03:10 Author: Admin

Clays were formed as a result of natural weathering of igneous feldspathic rocks - mainly granites, volcanic glass, tuffs, porphyrites, as well as due to the destruction of metamorphic rocks (gneisses), etc.

As a result of weathering, feldspars are transformed into a clayey substance, which is formed mainly in the form of kaolinite minerals according to the following scheme (for orthoclase):

The reasons for this decomposition of feldspathic rocks are physical (temperature fluctuations, freezing of water, crystallization of salts), chemical (under the influence of atmospheric oxygen, carbon dioxide, water, organic acids) and biological (vital activity of microorganisms) weathering. As a result of physical and chemical weathering on various rocks and deposits, a weathering crust appears.

Weathering crust minerals are formed in two ways - synthetically, for example, by converting feldspar into individual oxides - Al 2 O 3 and SiO 2
and by coagulation of these oxides into the mineral composition kaolinite, and by hydrolysis of primary minerals. The minerals kaolinite, illite (hydromica) and montmorillonite are the main rock-forming minerals of clay raw materials.

The word “clay” means fine-clastic sedimentary rock consisting of mineral particles less than 0.005 mm in size, chemically representing hydrous aluminosilicates and accompanying impurities of other minerals. Since granites, together with transitional varieties, make up approximately all igneous rocks, i.e. there are much more of them in nature than others, sedimentary rocks contain the largest amount of clay (as a decomposition product of the most common minerals of igneous rocks - feldspars, for example orthoclase , albite, anorthite).

It is estimated that the earth's crust consists of 95% igneous rocks and 5% sedimentary rocks, of which 4% are clays only. Clays can be primary, which remained in the place of their formation, and secondary, which were deposited in new places as a result of alluvial, deluvial, fluvio-glacial, aeolian and other processes. Primary clay, moving in one of these ways, for example, by water, could be freed from the impurities that originally accompanied it and therefore be deposited in a new place in a purer form, while improving in quality. This is how kaolins were formed, characterized by a high content of the mineral kaolinite, high fire resistance, and a low content of coloring oxides, as a result of which they acquire a predominantly white color before and after firing.

Clays with a slightly increased content of fluxes and coloring oxides are classified as a special type - refractory clays, and clays containing a significant amount of impurities (coloring oxides, fluxes, etc.) become fusible - ordinary clays. If we divide clay raw materials according to the area of application in industry, then pure white kaolins and some refractory clays (white-burning raw materials) are included in the groups of porcelain and earthenware, refractory - in the groups of pipe, clinker, terracotta, and low-melting clays - in the groups of pottery, brick-tile, expanded clay clays.

Clays of Quaternary and Upper Tertiary age, which especially often satisfy the requirements for clay raw materials for the production of bricks, tiles, expanded clay and other ceramic materials and products, are characterized by the presence of a significant admixture of sand particles and the polymineral nature of the clay part. Among the clay minerals in these rocks, hydromica usually predominates. Kaolinite and montmorillonite are of minor importance, and other minerals (chlorite, halloysite, etc.) are present as impurities.

Small amount kaolinite does not significantly affect the increase in firing temperature, and montmorillonite significantly reduces it, which is a valuable quality in the manufacture of building bricks. For the manufacture of some types of bricks and ceramic tiles in Russia, the USA and some other countries, loess rocks are used - widespread quaternary deposits containing, in addition to sand and clay, a lot of fine dusty material (50-70%).

Clay rocks can be in loose and stone-like states. But no matter what state these rocks are in, they contain a group of finely dispersed minerals that give the clay plasticity, the ability to be molded (for stone-like ones after fine grinding) and retain its given shape after drying. This group of minerals, which are hydrous aluminosilicates, is called clay or clay substance.

Except kaolinite clays are widely distributed in nature hydromica. They are formed as a result of weathering of silicate rocks in humid climates and are products of the first stage of chemical weathering. The main rock-forming minerals in these clays are hydromica, including glauconite, and the minor ones are kaolinite and montmorillonite. Primary hydromica clays are found in the weathering crust of crystalline rocks, secondary ones are represented by continental sediments - lake, river, glacial, marine (shelf) and lagoon sediments.

A special type of clayey rock is bentonite. It was formed by weathering of effusive rocks, tuffs, volcanic ash, etc. (it received this name from the name of the American Fort Benton, in the area of which it was first discovered).

Bentonite consists mainly of minerals of the montmorillonite group, but also contains impurities. It is used for the preparation of porcelain masses, washing solutions for drilling, as an adsorbent for liquid clarification,
when enriching iron ores, etc.

Polymineral clays are formed when sedimentary differentiation of matter is not perfect enough. Most of these clays are of secondary origin. They are widely developed in deluvial sediments, in alluvial deposits, rarely in marine sediments and sometimes in the weathering crust. They contain hydromica, kaolinite, montmorillonite, quartz, and micas. They are used for the manufacture of rough ceramic products. Some of their varieties are suitable for producing expanded clay.

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Clay- a plastic natural material used in construction, folk crafts, treatment and healing of the body and in other areas of human life. It is this widespread use that is determined by certain qualities and properties of clay. And the properties of clay are largely influenced by its composition.

Application of clay

Clay is very accessible, and its benefits are invaluable, and therefore it has been used by people since ancient times. There are many mentions of this wonderful material in history textbooks of all countries of the world.

Construction. Currently, clay is used as a material for making red bricks. Clay of a certain composition is molded and fired using a certain technology to obtain a durable and inexpensive ingot - a brick. And buildings and structures are already being built from brick. In some countries and regions, clay is still used to build houses - mud huts; the use of clay is widespread in the construction of brick ovens, where clay serves as a binder (as cement). The same clay is also used for plastering stoves.

Medicine. Wellness and traditional medicine uses clay in the form of mud baths and masks. The whole point is to nourish the surface of the skin with the beneficial elements of clay. Of course, not all clay will work here.

Souvenirs and dishes. I combine two large directions into one, since many examples of dishes are only of a souvenir nature. Plates, pots, jugs and vases are present in abundance in modern stores. Not a single fair is complete without selling clay souvenirs - smoky toys, whistles, signs, keychains and much more. You and I will try to create a lot of things ourselves.

Clay can be included in composition of other materials. Finely ground Chasovoyar clay, for example, is an element of artistic paints (gouache), sauce, pastels and sanguine. Read about this in the "Help to the Artist" articles.

Properties of clay

Color. Clay of various compositions has many shades. The clay is called by its colors: red, blue, white... However, upon drying and further firing, the color can completely change. This is worth paying attention to when working with clay.

Plastic. It was the ability to deform and retain the shape given to it that allowed man to find the use of clay in his everyday life. It is worth noting here that everything depends on the consistency - the ratio of the amount of water, clay and sand. Different jobs require different compositions. So, for sculpting, sand may be completely unnecessary.

Hygroscopicity allows clay to absorb water, changing its viscosity and plasticity properties. But after firing, clay products acquire water resistance, strength and lightness. The development of technology has made it possible to obtain earthenware and porcelain, which are indispensable in the modern world.

Fire resistance. A property used more in construction than in artistic crafts, except for the firing of products. The firing technology is different for a particular clay composition. Closely related to drying and firing is the property of clay shrinkage or compressibility - a change in mass and size due to the removal of part of the water from the composition.

Clay composition

The properties of clay are determined by its chemical composition. Different types of clay have different chemical compositions. For example, red clay contains a lot of iron oxides. Clay basically contains certain substances - clay minerals - that are formed during various natural phenomena. The format of the article does not provide for consideration of the chemical properties and composition of clay, so I will not go into detail.

The composition of clay suitable for use in folk crafts, as already mentioned, is determined by three important elements: clay minerals, water and sand.

The proportions of these elements can be changed, although it is much easier to add than to remove. So, for example, dry clay can be quickly dissolved, however, it is not at all easy to make clay as liquid as sour cream suitable for modeling. Sand is very easy to add, but removing it from the clay is a non-trivial task.

There are “lean” and “fat” clays. The “fat content” scale determines the plasticity coefficient, and the binding properties of clay allow you to regulate the fat content by mixing it with other natural materials, for example, sand. Lean clay has less plasticity, its binding force is weaker, but it shrinks less during drying and firing.

Clay deposits are found in varying states around the world. This ensured its use by artisans of different nationalities, and contributed to the emergence of such a variety of products and technologies.

Craftsmen have learned to control the behavior and condition of clay through various additions to the composition. This way you can thin the clay, elutriate it, give it greater fire resistance, and reduce shrinkage. As a result of such manipulations, an experienced craftsman will be able to ultimately obtain a high-quality, highly artistic product.

Typically, the chemical composition of low-melting clays is, %: SiO 2 – 60...85; Al 2 O 3 together with TiO 2 – no less than 7; Fe 2 O 3 together with FeO- no more than 14; CaO + MgO – no more than 20; R 2 O (K 2 O + Na 2 O) – no more than 7.

Comparative characteristics of the chemical composition of various clays are given in table. 1.

Table 1

Chemical composition of clays

Silica(SiO 2) is found in clays in bound and free states. The first is part of clay-forming minerals, and the second is represented by siliceous impurities. With an increase in SiO 2 content, the plasticity of clays decreases, porosity increases, and the strength of fired products decreases. The maximum content of SiO 2 is no more than 85%, including free quartz – no more than 60%.

Alumina(Al 2 O 3) is found in clay-forming minerals and mica impurities. With increasing Al 2 O 3 content, the plasticity and fire resistance of clays increases. Usually, the alumina content indirectly judges the relative size of the clay fraction in the clay rock. Alumina is contained from 10-15% in brick and up to 32-35% in refractory clays.

(CaO and MgO) participate in small quantities in the composition of some clay minerals. At high temperatures, CaO reacts with Al 2 O 3 and SiO 2 and, forming eutectic melts in the form of aluminum-calcium-silicate glasses, sharply lower the melting point of clays.

Alkaline earth metal oxides(Na 2 O and K 2 O) are components of some clay-forming minerals, but in most cases they are involved in impurities in the form of soluble salts and in feldspathic sands. They lower the melting point of clay and weaken the coloring effect of Fe 2 O 3 and TiO 2. Alkali metal oxides are strong fluxes and contribute to increased shrinkage, compaction of the shard and increase its strength.

The limit value of sulfur compounds in terms of SO 3 is taken to be no more than 2%, including sulfide - no more than 0.8%. In the presence of SO 3 more than 0.5%, including sulfide no more than 0.3%, in the process of testing clay rock, methods for eliminating efflorescence and efflorescence on unfired products should be determined by converting soluble salts to insoluble ones.

2.3. Granulometric composition of clays.

The granulometric composition of clays is the distribution of grains in a clay rock according to their size. Typically, the grain composition of various clays is characterized by the data given in Table 2.

Clay is a fine-grained sedimentary rock, dust-like when dry, plastic when moistened.

Origin of clay.

Clay is a secondary product formed as a result of the destruction of rocks during the weathering process. The main source of clay formations are feldspars, the destruction of which under the influence of atmospheric agents forms silicates of the group of clay minerals. Some clays are formed by the local accumulation of these minerals, but most are sediments from water flows that accumulate at the bottom of lakes and seas.

In general, according to their origin and composition, all clays are divided into:

- sedimentary clays, formed as a result of the transfer to another place and deposition there of clayey and other products of the weathering crust. Based on their origin, sedimentary clays are divided into marine clays, deposited on the seabed, and continental clays, formed on the mainland.

Among marine clays there are:

Coastal- are formed in coastal zones (turbulence zones) of seas, open bays, and river deltas. They are often characterized by unsorted material. They quickly change into sandy and coarse-grained varieties. Replaced by sandy and carbonate deposits along the strike. Such clays are usually interbedded with sandstones, siltstones, coal seams and carbonate rocks.
Lagoon- are formed in sea lagoons, semi-enclosed with a high concentration of salts or desalinated. In the first case, the clays are heterogeneous in granulometric composition, insufficiently sorted and wind together with gypsum or salts. Clays from desalinated lagoons are usually finely dispersed, thin-layered, and contain inclusions of calcite, siderite, iron sulfides, etc. Among these clays there are fire-resistant varieties.
Offshore- are formed at a depth of up to 200 m in the absence of currents. They are characterized by a uniform granulometric composition and large thickness (up to 100 m or more). Distributed over a large area.

Among the continental clays there are:

Deluvial- characterized by a mixed granulometric composition, its sharp variability and irregular layering (sometimes absent).
Ozernye with a uniform granulometric composition and finely dispersed. All clay minerals are present in such clays, but kaolinite and hydromicas, as well as minerals of hydrous oxides Fe and Al, predominate in clays of fresh lakes, and minerals of the montmorillonite group and carbonates predominate in clays of salt lakes. Lake clays include the best varieties of fire-resistant clays.
Proluvial, formed by temporary flows. Characterized by very poor sorting.
River- developed in river terraces, especially in the floodplain. Usually poorly sorted. They quickly turn into sands and pebbles, most often non-layered.

Residual - clays resulting from the weathering of various rocks on land, and in the sea as a result of changes in lavas, their ashes and tuffs. Down the section, residual clays gradually transform into parent rocks. The granulometric composition of residual clays is variable - from fine-grained varieties in the upper part of the deposit to uneven-grained ones in the lower part. Residual clays formed from acidic massive rocks are not plastic or have little plasticity; Clays formed during the destruction of sedimentary clay rocks are more plastic. Continental residual clays include kaolins and other eluvial clays. In the Russian Federation, in addition to modern ones, ancient residual clays are widespread - in the Urals, in the West. and Vost. Siberia (there are also many of them in Ukraine) - of great practical importance. In the mentioned areas, clays predominantly montmorillonite, nontronite, etc. appear on basic rocks, and on medium and acidic rocks - kaolins and hydromica clays. Marine residual clays form a group of bleaching clays composed of minerals of the montmorillonite group.

Clay is everywhere. Not in the sense - in every apartment and plate of borscht, but in every country. And if there are not enough diamonds, yellow metal or black gold in some places, then there is enough clay everywhere. Which, in general, is not surprising - clay, sedimentary rock, is a stone worn by time and external influences to the state of powder. The last stage of stone evolution. Stone-sand-clay. However, the last one? And sand can form into stone - golden and soft sandstone, and clay can become brick. Or a person. Who's got some luck?

The clay is colored by the creator stone and salts of iron, aluminum and similar minerals that happen to be nearby. Various organisms reproduce, live and die in clay. This is how red, yellow, blue, green, pink and other colored clays are obtained.

Previously, clay was mined along the banks of rivers and lakes. Or they dug a hole specifically for it. Then it became possible not to dig the clay yourself, but to buy it from a potter, for example. During our childhood, we dug out ordinary red clay ourselves, and bought noble white clay in artists’ stores or, especially pure clay, in a pharmacy. Now a nice little shop selling cosmetics will certainly have clay. True, not entirely in its pure form, but mixed with various detergents, moisturizers and nourishing agents.

Our land is rich in clay. Roads and paths cut into loamy soil become sources of dust in the heat, and in slush they become pure mud. Clay dust covered the traveler from head to toe and added to the housework of the housewives whose house stood by the road. Surprisingly, there was no less dust near roads covered with asphalt. True, he turned from red to black. Ledum, thickly mixed with clay, not only prevents a pedestrian from walking and a wheel from moving, but also, depending on the mood, you don’t mind swallowing a boot or a jeep.

Clay consists of one or more minerals of the kaolinite group (derived from the name of the locality Kaolin in the People's Republic of China (PRC)), montmorillonite, or other layered aluminosilicates (clay minerals), but may also contain sand and carbonate particles. As a rule, the rock-forming mineral in clay is kaolinite, its composition is: 47% silicon (IV) oxide (SiO 2), 39% aluminum oxide (Al 2 O 3) and 14% water (H 2 0). Al2O3 And SiO2- constitute a significant part of the chemical composition of clay-forming minerals.

The diameter of clay particles is less than 0.005 mm; Rocks consisting of larger particles are usually classified as loess. Most clays are gray in color, but there are clays in white, red, yellow, brown, blue, green, purple and even black. The color is due to impurities of ions - chromophores, mainly iron in valence 3 (red, yellow) or 2 (green, bluish).

Dry clay absorbs water well, but when wet it becomes waterproof. After kneading and mixing, it acquires the ability to take different shapes and retain them after drying. This property is called plasticity. In addition, clay has a binding ability: with powdery solids (sand) it produces a homogeneous “dough” that also has plasticity, but to a lesser extent. Obviously, the more sand or water admixtures in the clay, the lower the plasticity of the mixture.

According to the nature of the clays, they are divided into “fat” and “lean”.

Clays with high plasticity are called “fat” because when soaked they give a tactile sensation of a fatty substance. “Fatty” clay is shiny and slippery to the touch (if you take such clay on your teeth, it slips), and contains few impurities. The dough made from it is tender. Bricks made from such clay crack when dried and fired, and to avoid this, so-called “lean” substances are added to the mix: sand, “lean” clay, burnt brick, potter’s scrap, sawdust and etc.

Clays with low plasticity or non-plasticity are called “lean”. They are rough to the touch, with a matte surface, and when rubbed with a finger, they easily crumble, separating earthy dust particles. “Skinny” clays contain a lot of impurities (they crunch on the teeth); when cut with a knife, they do not produce shavings. Bricks made from “lean” clay are fragile and crumbly.

An important property of clay is its relationship to firing and, in general, to elevated temperatures: if soaked clay in air hardens, dries and is easily wiped into powder without undergoing any internal changes, then at high temperatures chemical processes occur and the composition of the substance changes.

At very high temperatures, clay melts. The temperature of melting (beginning of melting) characterizes the fire resistance of clay, which is not the same for its different varieties. Rare types of clay require colossal heat for firing - up to 2000°C, which is difficult to obtain even in factory conditions. In this case, there is a need to reduce fire resistance. The melting temperature can be reduced by adding the following substances (up to 1% by weight): magnesia, iron oxide, lime. Such additives are called fluxes (fluxes).

The color of the clays is varied: light gray, bluish, yellow, white, reddish, brown with various shades.

Minerals contained in clays:

Kaolinite (Al2O3 2SiO2 2H2O)
Andalusite, disthene and sillimanite (Al2O3 SiO2)
Halloysite (Al2O3 SiO2 H2O)
Hydrargillite (Al2O3 3H2O)
Diaspore (Al2O3 H2O)
Corundum (Al2O3)
Monothermite (0.20 Al2O3 2SiO2 1.5H2O)
Montmorillonite (MgO Al2O3 3SiO2 1.5H2O)
Muscovite (K2O Al2O3 6SiO2 2H2O)
Narkite (Al2O3 SiO2 2H2O)
Pyrophyllite (Al2O3 4SiO2 H2O)

Minerals contaminating clays and kaolins:

Quartz(SiO2)
gypsum (CaSO4 2H2O)
dolomite (MgO CaO CO2)
Calcite (CaO CO2)
Glauconite (K2O Fe2O3 4SiO2 10H2O)
Limonite (Fe2O3 3H2O)
Magnetite (FeO Fe2O3)
Marcasite (FeS2)
Pyrite (FeS2)
Rutile (TiO2)
Serpentine (3MgO 2SiO2 2H2O)
Siderite (FeO CO2)

Clay appeared on earth many thousands of years ago. Its “parents” are considered to be rock-forming minerals known in geology - kaolinites, spars, some varieties of mica, limestones and marbles. Under certain conditions, even some types of sand transform into clay. All known rocks that have geological outcrops on the surface of the earth are subject to the influence of the elements - rain, whirlwind storms, snow and flood waters.

Temperature changes day and night and heating of the rock by the sun's rays contribute to the appearance of microcracks. Water gets into the cracks that form and, freezing, breaks the surface of the stone, forming a large amount of tiny dust on it. Natural cyclones crush and grind dust into even finer dust. Where the cyclone changes its direction or simply dies down, huge accumulations of rock particles form over time. They are pressed, soaked in water, and the result is clay.

Depending on what rock the clay is formed from and how it is formed, it acquires different colors. The most common clays are yellow, red, white, blue, green, dark brown and black. All colors, except black, brown and red, indicate the deep origin of the clay.

The colors of clay are determined by the presence of the following salts in it:

red clay - potassium, iron;
greenish clay - copper, ferrous iron;
blue clay - cobalt, cadmium;
dark brown and black clay - carbon, iron;
yellow clay - sodium, ferric iron, sulfur and its salts.

Various colored clays.

We can also give an industrial classification of clays, which is based on the assessment of these clays based on a combination of a number of characteristics. For example, this is the appearance of the product, color, sintering (melting) interval, resistance of the product to sudden changes in temperature, as well as the strength of the product to impacts. Based on these characteristics, you can determine the name of the clay and its purpose:

china clay
earthenware clay
white-burning clay
brick and tile clay
pipe clay
clinker clay
capsule clay
terracotta clay

Practical use of clay.

Clays are widely used in industry (in the production of ceramic tiles, refractories, fine ceramics, porcelain-faience and sanitary ware), construction (production of bricks, expanded clay and other building materials), for household needs, in cosmetics and as a material for artistic works ( modeling). Expanded clay gravel and sand produced from expanded clay by annealing with swelling are widely used in the production of building materials (expanded clay concrete, expanded clay concrete blocks, wall panels, etc.) and as a heat and sound insulating material. This is a lightweight porous building material obtained by firing low-melting clay. It has the shape of oval granules. It is also produced in the form of sand - expanded clay sand.

Depending on the clay processing mode, expanded clay of different bulk density (volume weight) is obtained - from 200 to 400 kg/M3 and higher. Expanded clay has high heat and noise insulation properties and is used primarily as a porous filler for lightweight concrete, which has no serious alternative. Expanded clay concrete walls are durable, have high sanitary and hygienic characteristics, and expanded clay concrete structures built more than 50 years ago are still in use today. Housing built from prefabricated expanded clay concrete is cheap, high quality and affordable. The largest producer of expanded clay is Russia.

Clay is the basis of pottery and brick production. When mixed with water, clay forms a dough-like plastic mass suitable for further processing. Depending on the place of origin, natural raw materials have significant differences. One can be used in its pure form, the other must be sifted and mixed to obtain a material suitable for the manufacture of various trade items.

Natural red clay.

In nature, this clay has a greenish-brown color, which is given to it by iron oxide (Fe2O3), which makes up 5-8% of the total mass. When fired, depending on the temperature or type of oven, the clay acquires a red or whitish color. It kneads easily and can withstand heating of no more than 1050-1100 C. The great elasticity of this type of raw material allows it to be used for working with clay plates or for modeling small sculptures.

White clay.

Its deposits are found all over the world. When wet, it is light gray, and after firing it becomes whitish or ivory. White clay is characterized by elasticity and translucency due to the absence of iron oxide in its composition.

Clay is used to make dishes, tiles, and plumbing items, or for crafts made from clay plates. Firing temperature: 1050-1150 °C. Before glazing, it is recommended to work in an oven at a temperature of 900-1000 °C. (Firing of unglazed porcelain is called bisque firing.)

Porous ceramic mass.

Clay for ceramics is a white mass with a moderate calcium content and high porosity. Its natural color ranges from pure white to greenish-brown. Fires at low temperatures. Unfired clay is recommended, as for some glazes a single firing is not sufficient.

Majolica is a type of raw material made from fusible clay with a high content of white alumina, fired at a low temperature and covered with a glaze containing tin.

The name "majolica" comes from the island of Mallorca, where it was first used by the sculptor Florentino Luca de la Robbia (1400-1481). Later this technique was widespread in Italy. Ceramic trade items made from majolica were also called earthenware, since their production began in workshops for the production of earthenware.

Stone ceramic mass.

The basis of these raw materials are fireclay, quartz, kaolin and feldspar. When wet it has a black-brown color, and after wet firing it has an ivory color. When applying glaze, stone ceramics are transformed into a durable, waterproof and fireproof product. It can be very thin, opaque or in the form of a homogeneous, densely sintered mass. Recommended firing temperature: 1100-1300 °C. If it is disturbed, the clay may crumble. The material is used in various technologies for making commercial pottery items from lamellar clay and for modeling. Trade items made of red clay and stone ceramics are distinguished depending on their technical properties.

Clay for porcelain trade objects consists of kaolin, quartz and feldspar. It does not contain iron oxide. When wet it has a light gray color, after firing it is white. Recommended firing temperature: 1300-1400 °C. This type of raw material is elastic. Working with it on a pottery wheel requires high technical costs, so it is better to use ready-made forms. This is a hard, non-porous clay (with low water absorption - Ed.). After firing, the porcelain becomes transparent. Glaze firing takes place at a temperature of 900-1000 °C.

Various porcelain trade items, molded and fired at 1400°C.

Large-pored, coarse-grained ceramic materials are used for the manufacture of large-sized commercial items in construction, small-form architecture, etc. These varieties can withstand high temperatures and thermal fluctuations. Their plasticity depends on the content of quartz and aluminum (silica and alumina - Ed.) in the rock. The overall structure contains a lot of alumina with a high chamotte content. The melting point ranges from 1440 to 1600 °C. The material sinteres well and shrinks slightly, so it is used to create large objects and large-format wall panels. When making artistic objects, the temperature should not exceed 1300°C.

This is a clay mass containing an oxide or colorful pigment, which is a homogeneous mixture. If, penetrating deep into the clay, part of the paint remains suspended, then the even tone of the raw material may be disrupted. Both colored and ordinary white or porous clay can be purchased in specialized stores.

Masses with colored pigment.

Pigments- these are inorganic compounds that color clay and glaze. Pigments can be divided into two groups: oxides and colorants. Oxides are a naturally occurring basic material that forms among the rocks of the earth's crust, is purified and atomized. The most commonly used are: copper oxide, which takes on a green color in the oxidizing firing environment; cobalt oxide, which produces blue tones; iron oxide, which gives blue tones when mixed with glaze, and earth tones when mixed with clay. Chromium oxide gives the clay an olive green color, magnesium oxide gives it brown and purple tones, and nickel oxide gives it a grayish-green color. All these oxides can be mixed with clay in a proportion of 0.5-6%. If their percentage is exceeded, the oxide will act as a flux, lowering the melting point of the clay. When painting trade items, the temperature should not exceed 1020 °C, otherwise firing will not produce results. The second group is dyes. They are obtained industrially or by mechanical processing of natural materials, which represent a full range of colors. Dyes are mixed with clay in a proportion of 5-20%, which determines the light or dark tone of the material. All specialized stores have an assortment of pigments and dyes for both clay and engobes.

Preparing ceramic mass requires a lot of attention. It can be composed in two ways, which give completely different results. A more logical and reliable way: add dyes under pressure. A simpler and, of course, less reliable method: mix dyes into the clay by hand. The second method is used if there is no exact idea about the final coloring results or there is a need to repeat certain colors.

Technical ceramics.

Technical ceramics is a large group of ceramic trade items and materials obtained by heat treatment of a mass of a given chemical composition from mineral raw materials and other high-quality raw materials that have the necessary strength, electrical properties (high volumetric and surface resistivity, high electrical strength, small tangent angle dielectric losses).

Cement production.

To make cement, calcium carbonate and clay are first extracted from quarries. Calcium carbonate (approximately 75% of the quantity) is crushed and thoroughly mixed with clay (approximately 25% of the mixture). Dosing of starting materials is an extremely difficult process, since the lime content must correspond to the specified amount with an accuracy of 0.1%.

These ratios are defined in the specialized literature by the concepts of “calcareous”, “siliceous” and “alumina” modules. Since the chemical composition of the starting raw materials constantly fluctuates due to geological origin, it is easy to understand how difficult it is to maintain a constant modulus. In modern cement plants, computer control in combination with automatic analysis methods has proven itself well.

Properly composed sludge, prepared depending on the chosen technology (dry or wet method), is introduced into a rotary kiln (up to 200 m long and up to 2-7 m in diameter) and fired at a temperature of about 1450 °C - the so-called sintering temperature. At this temperature, the material begins to melt (sinter), it leaves the kiln in the form of more or less large lumps of clinker (sometimes called Portland cement clinker). Firing occurs.

As a result of these reactions, clinker materials are formed. After leaving the rotary kiln, the clinker enters the cooler, where it is sharply cooled from 1300 to 130 °C. After cooling, the clinker is crushed with a small addition of gypsum (maximum 6%). The size of cement grains ranges from 1 to 100 microns. It is better illustrated by the concept of “specific surface area”. If we sum up the surface area of the grains in one gram of cement, then, depending on the grinding thickness of the cement, we get values from 2000 to 5000 cm² (0.2-0.5 m²). The predominant part of cement in special containers is transported by road or rail. All overloads are performed pneumatically. A minority of cement products are delivered in moisture- and tear-resistant paper bags. Cement is stored at construction sites mainly in liquid and dry states.

Supporting Information.

Clay refers to secondary rocks that were formed as a result of weathering of rock masses during the evolutionary process. Clay is used more often than other materials as a building material. The composition of clay is very complex and variable. In its pure form, clay contains practically no impurities. The diameter of its particles does not exceed 0.01 mm; as a rule, clay is plastic. All types of clays contain chemically bound water; it is retained in the form of thin films between particles of clay material.

The clay contains silicon and aluminum components. The most common impurities are iron hydroxide, alkali earth metal oxides, quartz and iron sulfide. Rocks with a high alumina content are used to produce refractory materials; the alumina content in such rocks ranges from 25 to 30%.

When all types of clays get wet, water fills the gaps between the particles, as a result of which they easily move relative to each other. This property determines the plasticity of clay materials.

Clay material is widespread in nature. Clays are divided into subgroups depending on the mineral composition and particle diameter, the presence of certain impurities. There are these types of clay:

red,
white,
sandy,
clay for porcelain,
kaolin

The granulometry of certain types of materials depends on the mineral components and chemical composition. Almost all varieties of this unique fossil are characterized by plasticity, adsorption, and swelling. When wet, shrinkage and swelling are characteristic; these properties are decisive when using the material in industry.

According to industrial technical requirements, rock is divided into varieties:

low-melting,
refractory,
adsorption,
kaolin

Soaked clay becomes plastic and can take almost any shape.

Plastic masses are called “greasy” because they feel like a greasy material to the touch. Varieties of clays with a low degree of plasticity are called “lean” or lean. Products made from such materials quickly crumble; “lean” clay is not suitable for brick production.

Dried clay holds the shape it was given well, while it slightly decreases in volume, compacts, hardens and becomes as strong as stone. Due to these properties, clay has long been considered the most widely used material for making dishes and other household items.
Among other things, this breed has the ability to be sticky.
Having absorbed a certain amount of moisture, the material no longer allows water to pass through; this property determines the water resistance of the material.
Another property of clay is its covering ability. Due to this property, clay has long been used to cover the walls of buildings and furnaces.
The sorption capacity of the material makes it possible to use clay as a purifier of fats and petroleum products.

All of the above properties ensure a long service life for objects made from clay.

Types of clay and their origin

Based on their origin, clayey materials are divided into subgroups.

Sedimentary clays. They are formed as a result of the application of destroyed rock layers by water flows. These materials are divided into marine and continental. From the name of the first it is clear that clay is formed on the seabed, in the second case the formation occurs on continents, in the bottom sediments of rivers and lakes.

Under natural conditions, this variety has a brown tint; it is given to the material by iron-containing compounds - ferrum oxides, which are contained in clay in an amount of 5 to 9%. These are usually sedimentary clays. They are formed as a result of the application of water to destroyed rock layers.

During the firing process, red clay turns red or white, depending on the process conditions and the type of firing equipment. This variety can withstand heating up to 1100 degrees.

This type of clay is flexible and kneads well. The high elasticity of the material determines its use as a material for sculptural modeling.

Natural mineral deposits are found everywhere. They often accumulate in sea or fresh lagoons. In the case of sea bays, clay is a heterogeneous mass and has numerous impurities.

When wet, the clay acquires a light gray tint; as a result of the firing process, it turns into a beautiful white material. This type of clay is characterized by elasticity.
Due to the absence of iron compounds, white clay is slightly translucent. It is widely used for the production of household items, dishes, jugs, and decorative figurines. In addition, the material is used in the production of tiles and sanitary ware.
Objects made from this clay are covered with glaze, kept in ovens at 900-950 degrees.

Porous mass for ceramic production

The raw material is a clayey material with a low calcium content and high porosity.

This clay consists of kaolinite, illite and other aluminosilicates, and also contains inclusions of sand and carbonates. Silica and alumina are the basis of clay minerals.
Porous mass refers to sedimentary types of clay. It is formed as a result of the application of water to destroyed rock layers.
The natural color of such clay ranges from white to brown. Greenish clays are also found. The material is fired at low temperatures.

Majolica

This is a low-melting type of clay material that contains a large amount of white alumina. The raw materials are fired at low temperatures. Majolica is glazed with special mixtures containing tin compounds.

The word “majolica” comes from the name of the island of Majorca, where this material was used for the first time. Majolica was widely used in Italy. Traditionally, objects made from majolica are called earthenware, because for the first time they began to be produced in special departments for the production of earthenware.

Fireplace clay mass

The composition of this rock includes quartz, a significant amount of feldspar and fireclay. These are shelf rocks by origin. They are formed at a depth of about two hundred meters. A prerequisite is the absence of any kind of currents.

Black material. After firing, the mass resembles ivory products in color. Thanks to the use of glaze, products made from raw materials become unusually durable and have high water resistance.

This raw material is a baked mass. It is fired at a temperature of 1100 - 1300 degrees. The firing process is carried out under careful supervision in compliance with technological rules, otherwise the clay products may crumble.

Stone ceramic mass is used for modeling and for the manufacture of various ceramic objects. Products made from this material are very beautiful. Stone ceramics has unique technical properties.

The raw material includes feldspar, a significant amount of quartz and kaolin. This type of clay does not contain iron impurities.

When wetted with water, the mass acquires a gray tint, and after the firing process it becomes perfectly white. The material is fired in ovens at a temperature of 1300 - 1400 degrees. This raw material is very elastic.

It is not recommended to use this variety for working on pottery wheels. The material is very dense, practically without pores, water absorption is very low. The burned material becomes transparent. Objects made from porcelain clay material are coated with various glazes.

Materials for rough ceramics

Large-porous clay is used for the production of large objects and is often used in construction. Products of the material are characterized by high heat resistance; they can withstand temperature fluctuations well.

The plastic properties of raw materials depend on the presence of quartz and aluminum in the compound. The characteristic features of the material are due to the presence of a significant content of fireclay and alumina.

The material belongs to the refractory variety. Melting point – 1400-1600 degrees. The coarse ceramic material sinteres perfectly and practically does not shrink. These properties determine its use for the production of dimensional objects, as well as large panels and mosaics.

Montmorillonite clay

The raw material is used as a bleaching agent in the purification of tent syrups, in brewing, in the production of juice and refined oils. This material improves the quality of finished products; in addition, this type of clay is used as a means to combat rodents and insects.

Adsorption clay

A characteristic feature is high binding properties and a high degree of catalysis. The most common adsorption clay is bentonite.

Colored clay materials

Multi-colored clay is a material that contains oxides of metallic elements or pigments, and is a homogeneous mixture.

When pigments penetrate into the thickness of the material, some of them remain in suspension, and the uniformity of the tone of the raw material is disrupted.
Natural pigments give clay a particular shade; they are divided into two categories: oxides of metal elements and coloring substances themselves.
Oxides are natural components of natural origin, formed in the thickness of the earth. These substances are purified and finely ground. Copper oxide is most often used to give clay a particular color. During the firing process, this substance acquires a greenish tint as a result of the oxidation process.
To give the material a blue tint, oxygen-containing cobalt compounds are used. Chromium compounds provide the color of olives, while magnesium and nickel compounds provide brown and gray, respectively.
Coloring components are added to raw materials in amounts from 1 to 5%. Higher pigment contents may cause undesirable effects during the firing process.

Scope of application

Clay is actively used in construction for the manufacture of bricks and ceramic products. It has undeniable advantages, as well as a relatively low cost. The advantages of this raw material include heat resistance, adsorption properties, environmental friendliness, and breathability.