Doctors say that medicinal and cosmetic clays are not just a basis for medicines, but substances that are medicines in themselves. Leaving indoor application this substance to doctors, let's talk about how it helps make the skin healthy and beautiful.
What is it?
From a geological point of view, clay is a substance that arose due to the destruction of rocks under the influence of water and wind for many years.
From a chemical point of view, it is a mixture of silicon oxide and aluminum oxide with admixtures of coloring ions and organic substances. Silicon prevents skin aging, smoothes wrinkles, and accelerates healing processes. Aluminum oxide in the form of tiny particles (not exceeding 1 micron) gently exfoliates dead particles of the epidermis, making the skin smooth and soft. It also has a drying, astringent effect. In addition, useful macro- and microelements include phosphates, nitrogen, and iron.
Clay is capable of absorbing and retaining water and substances dissolved in it, including toxic ones. This property is used not only in cosmetology, but also by doctors in the treatment of diseases of the gastrointestinal tract. Actually, this property contains the answer to the question “does cosmetic clay draw out toxins from the skin?”
From a physics point of view, this is a good coolant. The local thermal effect is especially useful for: capillaries expand, microcirculation improves. This effect can also be useful in the treatment of diseases of the joints, muscles and ligaments.
Thus, cosmetic clay, used in our case for the face, has the following properties:
- cleansing and detoxification,
- peeling,
- moisturizing the skin surface ( important condition: the mask must not be allowed to dry),
- mineralization of the skin,
- calming effect (relieves redness, irritation and swelling),
- enhances the effectiveness of cosmetics (improves their penetration due to a tight fit).
The shelf life of “pure” (without additional cosmetic ingredients) clay dried to powder is practically unlimited.
Can clay cause allergies? No, he can not. provoke allergic reaction Added active ingredients, such as essential oils, can. You can check the reaction using a standard skin test: apply a small amount of the mixture prepared in the required proportions in the area of the elbow, leave for half an hour, rinse, and after a day evaluate the condition of the skin at the application site.
To prepare masks or wraps, only ceramic, glass or plastic are used - in no case metal! - dishes. The spatula for spreading and applying the mask should also not be metal.
The oilier the skin, the longer you can keep the mask on it, and the shorter the break between procedures. Ladies with dry skin are not recommended to apply the mask for more than 5 minutes once a week. Oily skin allows you to keep the mask for 15 minutes and use it every other day.
Types of cosmetic clay and their properties
White
Also known as kaolin. The most common, chemically neutral, due to which it is used in the pharmacopoeia as a filler for mixing substances that are destroyed upon contact with organic matter. In the same way, it is inert when in contact with the skin: from the white clay itself (without additional components) no substances pass into the skin tissue chemical substances. But at the same time, cell waste products, pathogenic bacteria, and inflammatory products are perfectly removed. Due to this property, kaolin has a good soothing effect - for neurodermatitis, it reduces swelling and itching.
A mask diluted with water is best for oily skin.
- As a soft scrub:
Dilute the powder with water 1 to 1, apply to the face, massage for 5 minutes, not allowing it to dry out. Wash with cool water.
- As a drying mask for excessive sebum (sebum) production:
Apply the powder diluted 1 to 1 on the face for 10-12 minutes. Rinse off the dried mask with cool water.
Green
Another great option for oily skin. Narrows pores, normalizes the secretion of sebaceous glands, tones. It contains elements such as silver, magnesium, calcium, zinc, cobalt, phosphorus, copper. They improve metabolic processes and help strengthen skin tissue.
- Acne mask
For 1 heaping tablespoon of powder, take ½ teaspoon of grape seed oil and add 3-5 drops of tea tree essential oil. Dilute with water to the consistency of thick sour cream. Apply to face for 10-15 minutes, rinse with warm (not hot!) water.
- Mask for blackheads (comedones)
Add 5-10 drops to 1 tablespoon of powder lemon juice, add water until the consistency of thick sour cream. Keep on your face for 10-15 minutes, avoiding drying (you can spray your face with water). Rinse off.
Blue
Whitens the skin, tones it, and can smooth out fine wrinkles.
- Whitening mask
Mix equal amounts of blue clay, tomato juice and sour milk.
But the best use cosmetic clay blue color– for the body, as an anti-cellulite wrap.
How to do wraps
Before the wrapping procedure, you must do peeling. Dilute the clay with warm water to a paste consistency. Heat in a water bath to a temperature of about 40-45 degrees: the mixture should be hot, but comfortable for the body. If desired, you can add essential oils of lemon, orange, grapefruit, cedar, rosemary (the latter is best not combined with other oils) - but even without them, the wrap is very effective. Apply the mixture to problem areas of the body in a thick layer, wrap in film, and cover with a blanket to prevent heat loss. The duration of the procedure is 20-40 minutes, the course is 8-10 procedures, which are carried out every other day. Clay wraps should not be used when high temperature, thyrotoxicosis, varicose veins, pregnancy, cancer.
Pink
Smoothes the skin texture, therefore it is used in masks against wrinkles.
- Mask for aging skin
Mix 2 tablespoons of powder with 1 tablespoon of almond oil, add warm water to the desired consistency. Keep on your face for 5-10 minutes without allowing it to dry out.
- Mask for dry skin
To 2 tablespoons of clay add a tablespoon of peach oil and 5 drops of patchouli oil. Rinse off after 5-10 minutes, do not allow it to dry out.
Red
Reduces irritation, improves blood circulation. Can be used for hot wraps with lipolytic and tonic properties. Good for baths too.
Photo taken from the resource Recommend.ru
Bath with red cosmetic clay
Helps against allergies, inflammation, abscesses. Shake 200 g of clay in the bath. If desired (and if skin tolerates it) add 1-2 handfuls sea salt. You can take such a bath no more than once every 2 weeks.
Red clay can be used not only in the form of baths, but also topically to treat abscesses. To do this, you need to dilute the powder thickly and spread it with a spatula on a piece of fabric in a layer about 2 cm thick. Apply to the affected area, bandage, leave for 40 minutes. The mixture cannot be reused. However, any type of clay can be used in this way: its adsorbing and antibacterial properties will have an effect. Under no circumstances should you heat an abscess!
Black clay
Not recommended for dry and sensitive skin. But for oily people it is optimal. If the question arises, which clay to choose for problem skin, the best option– black. It perfectly absorbs excess fat, inflammatory products, narrows pores, stimulates microcirculation and lymph flow, reducing swelling.
- Deep cleansing mask
To two tablespoons of clay add a teaspoon of calendula tincture and lemon juice. Leave for 10-15 minutes, be sure to apply moisturizer after the mask.
- Homemade scrub
To a tablespoon of powder, add a teaspoon of finely ground coffee, 2 drops of essential oil, and water until the consistency of sour cream. Apply to face, leave for 5 minutes without letting it dry, rinse, massaging gently. This scrub will be good for young skin, but for mature or sensitive skin it is better to limit yourself to just a pure mixture without additives. However, as an anti-cellulite remedy it is quite good at any age.
Using cosmetic clay for hair
The properties of clay to adsorb various substances allow it to be used not only for the face. Shampoos and hair masks based on it - simple and inexpensive way improve their appearance. These masks are especially good for. Their use helps reduce hair loss and increase breaks between washes. Since dirt is a mixture of excess sebum and dust, clay makes an excellent shampoo. In order to use it in this capacity, clay gruel is generously applied to the scalp, massaged for several minutes and rinsed thoroughly. After clay shampoo, be sure to rinse your hair with acidified water.
- Natural dry shampoo made from pink clay
Mix 5 tablespoons of powder with the same amount of mustard, add a tablespoon of salt, 5 drops each of tea tree and mint oil. Apply to damp scalp, massage thoroughly, rinse. Use balm as desired.
- Shampoo made from cosmetic clay and soda
To 6 parts clay add 1 part talc and 1 part soda.
- Shampoo with horsetail for very oily hair
In a glass of warm horsetail decoction, stir 2 tbsp. l. clay, apply to hair, leave for 5-10 minutes, rinse thoroughly.
- Moisturizing mask-shampoo
3-5 teaspoons of powder, a teaspoon of honey, an yolk, a tablespoon of lemon juice, half a glass of kefir (approximately). Instead of kefir, you can use tea (for dark hair) or herbal infusion. Apply to the scalp and hair, cover with a bag and a scarf for half an hour to an hour, rinse thoroughly (but not with hot water!).
- Mask for dry hair
Mix 2 tablespoons of powder with an equal amount of avocado pulp puree, add a teaspoon olive oil, if necessary - water to the desired consistency. Leave on hair for 30 minutes.
Read about treating dry hair.
- Mask against hair loss
Mix clay with castor oil until thick as sour cream. Leave on hair for 30 minutes to an hour.
Get to know folk recipes for hair loss you can in the article “”.
- Mask for oily hair
Brew a tablespoon of dry nettle with a glass of boiling water. Strain. Dilute the clay with broth until it becomes thick like sour cream. Add half a teaspoon of natural apple cider vinegar. Keep for 30 minutes to an hour.
How to choose cosmetic clay
The dry powder should contain nothing other than clay. desired color. Some unscrupulous manufacturers add dyes: this becomes immediately noticeable during dilution. We recommend that you immediately throw away this product, so to speak: you never know what else the manufacturer decided to save on, and where he “dug up” it.
A quality product also does not contain fragrances.
Ready-made clay masks usually come in the form of a paste to which additional ingredients and water have been added. Of course, with an appropriate markup.
The finer the powder is ground, the softer the consistency of the finished mask will be.
Some manufacturers produce white clay in the form of granules - this is acceptable.
But foreign impurities, caked lumps and coarse unground residues are an indicator of low quality.
Conclusion
Despite the fact that clay is a natural cosmetic product suitable for any age, it has the most noticeable effect on young, oily or problem skin. Apply it "in pure form» Not recommended for those with dry and aging skin. In this case, it must be mixed with base and essential oils, herbal decoctions.
It is good to use body products, both as wraps and local applications. Instead of wraps, you can also use baths, but in this case the procedure is done once every two weeks.
Hair masks, like skin masks, work best when there is excess sebum and oily seborrhea. Lovers of natural dry shampoos will love homemade shampoos with clay as the main ingredient.
Clay is a mineral and is a sedimentary, fine-grained rock. When dry it is dusty, but when moistened it becomes plastic and can increase in size.
Description
The material contains one or more minerals of the kaolinite group. The base may be a mineral of the montmorillonite group and other layered aluminosilicates, which are also called clay minerals. May contain carbonate and sand particles.
The rock-forming mineral is kaolinite, which consists of silicon oxide in a volume of 47%, aluminum oxide - 39%, and water - 14%. Substantial part chemical composition yellow clay is Al 2 O 3 and SiO 2. The material can have the following colors:
- green;
- blue;
- brown;
- black;
- lilac.
The color is due to ion impurities, which are chromophores.
Main types
Clay is a mineral that has several types. Each of them has its own area of use. If the plasticity number reaches 0.27, then the material is called light. When this parameter exceeds the mentioned figure, the clay is heavy. Typically, the clay mined and sold largely consists of kaolin, which is used in pulp and paper industry and in the production of refractory products, as well as porcelain.
Clay is a mineral that is also represented construction variety, as well as clay shale. This material is used to make refractory bricks and also forms the basis of heat-resistant products. Among the species important place occupies bentonite. It is formed by the chemical breakdown of volcanic ash. In water, this variety swells and increases in volume several times. Used in drilling wells and in the production of drilling fluids.
Clay is a mineral, which is also represented by the fulling variety, which is valued for its bleaching properties when refining petroleum products. Filters are made from this type of clay, which are used in the purification of mineral and vegetable oils.
Another variety is lump clay, which is called pottery clay. It has found its application in the manufacture of dishes. Shale is an important raw material that, along with limestone, is used in the production of Portland cement. The most common in nature are:
- sandstone clay;
- white clay, which is kaolin;
- red clay.
The varieties are used for the production of refractory products, as well as earthenware and porcelain.
Basic properties
Clay is a mineral that has a number of properties, among them the following should be highlighted:
- air and fire shrinkage;
- plastic;
- sinterability;
- fire resistance;
- viscosity;
- color of ceramic shard;
- porosity;
- shrinkage;
- dispersion;
- swelling.
Clay is the most stable waterproofing material that does not allow moisture to pass through, which is one of the important qualities. Clay soil has stability. It is developed in wastelands and wastelands. The development of root vegetation in clay deposits is impossible.
To preserve the quality of groundwater, the material's water-impermeability is useful. Most of the high-quality artesian springs lie between the clay layers.
Technical characteristics and additional properties
Now you know whether clay is a mineral. However, this is not all there is to know about this rock. It is also important to become familiar with the basic characteristics, for example, the specific and volumetric gravity of ground clay, which is 1400 kg/m3. Fireclay clay has a characteristic value of 1800 kg/m3.
When the clay is in the form of a dry powder, its volume and specific gravity is 900 kg/m3. The density of wet clay is also important, which varies from 1600 to 1820 kg/m3. For dry, this figure is approximately 100 kg/m3. Dry raw materials have thermal conductivity that reaches 0.3 W/(m*K). For the material in a wet state, this parameter is 3.0 W/(m*K).
Symbol
The symbol for clay should be of interest to you if you are studying it. When a material contains sand impurities, it is indicated by strokes and dots. If there are boulders in the clay, then circles are added to the strokes. Shales have the same designation as laminated clay, these are long strokes, densely spaced and carried in the direction of the strata.
Sand and clay
Sand and clay are the minerals that are most common. They are formed during the destruction of rocks such as granite. Under the influence of water, sun and wind, granite is destroyed, this contributes to the formation of clay and sand. They differ in color from each other: sand is often yellow, sometimes gray, while clay is white or brown.
Sand consists of individual particles different sizes. The grains are not attached to each other. Therefore, sand is free-flowing. Clay consists of small particles, similar to scales, well bonded to each other. Sand is a sedimentary rock or may be artificial material from rock grains. It usually consists of almost pure quartz mineral, the substance being silicon dioxide.
The natural material has grains with sizes within 5 mm in diameter. The minimum value is 0.16 mm. Sand can be classified according to accumulation conditions. Taking this into account, the material is divided into the following types:
- alluvial;
- deluvial;
- nautical;
- lake;
- aeolian.
If sand appeared as a result of the activity of reservoirs, then it has a more rounded particle shape.
Properties of granite
Sand, clay, granite, limestone are minerals. If we look at granite in more detail, it is an igneous platonic rock of acidic composition. It is based on:
- potassium feldspar;
- plagioclase;
- quartz;
- biotite;
- muscovite
Granite is common in the continental crust. Its density reaches 2600 kg/m³, while the compressive strength is 300 MPa. The material begins to melt at 1215 °C. In the presence of pressure and water, the melting point decreases to 650 °C.
Granite is the most important rock of the earth's crust, it is widespread and makes up the majority of all components. Among the varieties of granites, alaskite and plagiogranite can be distinguished. The latter has a light gray color with a sharp predominance of plagioclase. Alaskite is a pink granite, it contains a sharp predominance of potassium-sodium feldspar.
Properties of limestone
Looking at the table of minerals: sand, clay, granite, limestone, you can focus on the latter. It is a sedimentary rock of organic or chemogenic origin. The basis is most often calcium carbonate in the form of crystals of different sizes.
Limestone is made up of marine animal shells and debris. The density of the material is 2.6 g/cm 3, its frost resistance is F150. The compressive strength is equivalent to 35 MPa, while the loss of strength in moisture-saturated conditions reaches 14%. The porosity of the material is 25%.
Finally
Clay is a sedimentary rock that, when combined with water, begins to soak and separate into individual particles. As a result, a suspension or plastic mass is formed. Clay dough is plastic, and when raw it can take any shape. After drying, the material retains it, but decreases in volume. Plastic clays are also called fatty clays, because they feel exactly like that to the touch. If the plasticity is low, then the material is called lean. Bricks made from it quickly crumble and have poor strength.
The rock is sticky and has a binding ability. It is saturated with a certain volume of water, and then no longer allows liquid to pass through, which indicates water resistance. Clay has a covering ability, so in the past it was widely used for whitewashing the walls of houses and stoves. Among the properties, sorption capacity should be highlighted. This is expressed in the ability to absorb substances dissolved in water. This characteristic allows the use of clay for purification of vegetable fats and petroleum products.
Clay is a product of weathering of rocks, mainly feldspar and mica. Earthquakes, strong winds, floods move rock layers from their place, crushing them to powder. Placed in cracks in the earth's crust, they harden over millions of years.
Cambrian clays are primary; they have not been washed out over millions of years, although they have been weathered. Other clays are called secondary clays, a product of deposition. Secondary clays are found among sedimentary strata of all types - continental, including lacustrine, coastal-lagoonal and marine.
Lake clays often have a monomineral kaolinite composition. Pure montmorillonite clays (bentonites) are usually formed as a result of the alteration of volcanic ash and pumice. In industry, there are 4 most important groups of clays: coarse ceramic, refractory and refractory, kaolins, adsorption and
highly dispersed montmorillonite.
Main chemical components clays are secondary minerals of simple composition: silicon dioxide (quartz, SiO„ 30-70%), aluminum hydroxide (AlO3, 10-40%) and H2O (5-10%). Present in clays are TiO2, iron hydroxide (Fe20„ FeO), MnO, MgO, CaO, K20, Na20.
In addition, during the weathering process, secondary minerals of a more complex structure (aluminum and ferrisilicates) are also formed. They are more highly dispersed than primary minerals. All secondary minerals complex composition have a lamellar structure and contain chemically bound water. Since these minerals are the most important integral part various clays, they are called clay, or clay, minerals (A.I. Boldyrev, 1974). With all the diversity clay materials they have general feature: they were formed during the chemical destruction of other minerals and therefore the sizes of their crystals are very small - only 1...5 microns in diameter.
Contains clay main role kaolinite, montmorillonite, hydromicas, spars, limestones, and marbles play. Based on the predominance of the clay mineral, mineral types of clays are distinguished: kaolinite, montmorillonite, hydromica, etc.
Minerals of the kaolinite group include kaolinite AL2Si2Os(OH4) and halloysite AL28i2Ol(OH4) x 2H?0, as well as some other minerals. Kaolinite clays contain approximately 20-25% silt particles (less than 0.001 mm), of which 5-10% particles are colloidal in size (less than 0.25 microns). Minerals of this group are quite common in many types of clays. Such clays have relatively low swelling and stickiness.
Bentonites are sedimentary rocks consisting of minerals of the montmorillonite group. These minerals have a layered crystalline structure like graphite or talc, that is, they consist of extremely thin scales that can slide over each other under mechanical influence. This is why these minerals feel greasy to the touch. Between the scales there are cavities into which water molecules easily penetrate. Due to this, bentonite clays swell strongly in water and form a plastic dough.
Of the montmorillonite group minerals in clays, the most common are montmorillonite AL2Si40|9(OH2) x n20, beidellite ALoSbOyfOH?) x n20, and nontronite Fe2Si40|o(OH3) x n20. Montmorri-lonite clays, unlike kaolinite clays, have high swelling, stickiness and cohesion.
For them it is very characteristic feature is high degree dispersion (up to 80% of particles are less than 0.001 mm, of which 40-45% are less than 0.25 microns).
Among clay minerals great place belongs to the minerals of the hydromica group. This group INCLUDES hydromuscovite (illite) KAb[(Si, Al)4O|0](OH)2 x pH,0, hydrobiotite K(Mg, Fe)3[(Al, Si)40io](OH)2 x pH20 and vermiculite (Mg, Fe++, Fe+++)2[(Al, Si)4O|0](OH)2 x nH20.
In addition to clay materials, all clays contain one or another amount of impurities that greatly affect the properties of clays.
Quartz is one of the most common minerals on Earth, consisting of only silicon dioxide - silica (Si02).
Feldspar is a mineral that, along with silica, necessarily contains alumina - aluminum oxide (A1203), as well as the oxide of one of the metals such as sodium, potassium, calcium.
Mica very easily splits into thin transparent plates. Mica contains silica, alumina and (often) compounds of iron, sodium, and magnesium.
Most often, these impurity minerals make up the sand present in the clay. Less commonly found in clay are grains of limestone, gypsum, and other rocks and minerals.
Different minerals have different effects on the properties of clay. Thus, quartz reduces its ductility, but increases strength.
Clay crystal lattice
Clay minerals vary in structure. Such important properties clays, such as solubility, volatility, viscosity and other properties that characterize the stability of the compound, are determined by the energy of the crystal lattice. Clay is a crystalline solid, i.e. it has a clear internal structure due to correct location particles in a strictly defined periodically repeating order. Particles in crystals (atoms, molecules or ions) are arranged regularly, forming the so-called spatial lattice of the crystal.
The crystal lattice of various clay minerals is built from the same elementary structural units, consisting of silicon and oxygen atoms, as well as aluminum, oxygen and hydrogen atoms. The composition of clay minerals may also include Fe, Mg, K, Mi and others. Clay minerals have a layered structure and belong to layered silicates. Layers of clay minerals consist of a combination of silicon-oxygen and oxygen-hydroxyaluminum compounds.
The unit cell of the silicon oxygen compound is a tetrahedron, the four vertices of which are occupied by 02" anions, and in the center of this tetrahedron there is a smaller Si cation.
The tetrahedron (SiC>4)4 is the main structural unit not only of clay minerals, but also of all naturally occurring compounds of silicon with oxygen (A.I. Boldyrev, 1974).
The excess negative charges of this unit cell can be neutralized by the addition of any cations or the connection of several tetrahedra through the vertices, when the oxygen ion is simultaneously associated with two silicon ions. For clay, the most typical compounds are those in which silicon-oxygen tetrahedra are connected into layers (or sheets) of a cyclic structure. In such a layer, for every two silicon ions there are five oxygen ions, which corresponds to the formula (Si20s)2
Silicon-oxygen tetrahedral layers can combine with a layer of oxygen-aluminum hydroxyl atoms, which form octahedra. In them, the aluminum ion is surrounded by oxygen atoms and hydroxide ions. Aluminum-hydroxyl octahedra are connected in the same way as silicon-oxygen tetrahedra - into octahedral networks or layers. They can be constructed by analogy with the mineral gibbsite Al(OH)3 or brucite Mg(OH)2.
Silicon-oxygen and oxygen-hydroxide-aluminum networks form so-called tetrahedral-octahedral layers and packets. When the tetrahedral and octahedral layers are connected, the 0?' ions of the tetrahedral layer, located at the vertices of the tetrahedra, become common to both layers, i.e., the 0?' ions will serve as a kind of “bridges” between the Si4~ ions of one layer and the ions AB3+ of another layer. This structure is the most stable, since the number of positive charges Si4+ and AC+ in this structure is equal to the number of negative charges 0? and he".
Minerals of the kaolinite group have a two-layer phystal lattice, the packets of which are formed from two layers connected through common oxygen atoms: a layer of silicon-oxygen tetrahedra and an aluminum-hydroxyl layer, which has a dioctahedral structure. Such two-layer stacks alternate at intervals in the crystal, giving it a plate-like structure. Kaolinite is not able to absorb water into the interstitial spaces and therefore does not have the ability to swell.
Minerals of the montmorillonite group according to their crystal chemical properties are divided into two groups:
Dioctahedral (montmorillonite, nontronite, beidellite);
Trioctahedral (saponite, hectorite).
Montmorillonite is a three-layer mineral. Its packets consist of an octahedral layer (di-octahedral structure), which is sandwiched between two tetrahedral layers.
The composition of these layers is not constant due to isomorphic substitutions. The silicon of tetrahedra can also be partially replaced by aluminum and iron, and in octahedra, in addition to aluminum ions, there can be magnesium ions. Unlike kaolinite, the interpacket distances of montmorillonite can vary. These distances vary depending on the amount of water between the bags. Because of this, montmorillonite has a high swelling ability.
Minerals of the hydromica group include hydromuscovite (illite), hydrobiotite, vermiculite and other hydrated varieties of micas. The absorption capacity of hydromicas is several times higher than that of kaolinite, but 2-3 times less than that of montmorillonite.
The structure of illite is similar to that of montmorillonite, with the only difference being that it crystal lattice there are numerous isomorphic substitutions. Thus, the Al3+ ion in the octahedral layers is replaced by the Fe3+ ion and the Mg?+ ion, and two aluminum ions are replaced by three magnesium ions with the replacement of octahedral voids. In illite, two aluminum ions in octahedra are often replaced by two magnesium ions, while excess negative charges are compensated by potassium ions, which are located in the interpacket spaces.
Aluminosilicates - zeolites - have "molecular sieves" used as catalysts in petrochemical industry for the production of high-octane gasoline. Zeolites are the best adsorbents for radioactive waste nuclear power plants. They have proven themselves to be excellent in removing radionuclides from the body of “liquidators”, as well as farm animals living in contaminated areas. Zeolites are vital for animals. Having eaten plenty of natural zeolites, the animals became healthier: they gained better weight, and the mortality rate among calves decreased. This is explained by the fact that zeolites are able to absorb harmful substances and supply the body with the components it lacks.
The most important physicochemical and water-physical properties of clay - absorption capacity, hydrophilicity, cohesion, stickiness, reaction of the environment - are directly dependent on the mineralogical composition.
Free and bound water in clay
Water molecules themselves are neutral. However, one has only to place dipole water molecules in the external electric field, as the dipole character of these molecules immediately begins to appear.
The hydration of hydrophilic colloids is also determined by electrostatic forces, i.e. due to electric charges, arising due to ionization. On the surface of colloidal clay particles, shells are formed consisting of water dipoles, oriented with their positive or negative end depending on the type of charge.
Thus, in hydrophilic colloids, i.e., in clay solutions, some part of the water is firmly bound to colloidal particles, while the other part plays the role of a medium in which colloidal micelles are located.
The properties of bound water differ sharply from the properties of free water. In terms of the degree of ordering of the structure, bound water approaches the properties solid and has a higher density compared to free water. Hydration shells high molecular weight compound do not have solvent properties, so the high molecular weight substance dissolves only in free water. Bound water does not freeze when the clay solution cools, while free water is susceptible to freezing.
Metabolism in clay
Clays are often found under a layer of sand and soil. When minerals and organic residues are washed out of the soil, they end up on the clay substrate. Their most intensive penetration occurs in top layer clays 10-15 cm thick. In the Orenburg region, a deposit of Miocene sub-coal clay has been explored and used (N.P. Toropova et al., 2000).
Clay is an excellent “exchange point” for ions of mineral waters. At the same time, the composition of clay is greatly influenced by natural mineral water. So, if calcium sulfate (or magnesium) The groundwater migrate among clay rocks of marine origin, usually containing exchangeable sodium, then the following reactions occur:
clay = 2Na+ + Ca++ + SO4<-»2Na+ + SO4 + глина = Са++
clay = 2Na+ + Mg++ + SO4<->2Na+ + SO4 + clay = Mg++
The symbol “clay=Ca++” denotes clay containing exchangeable calcium (or another exchangeable cation). This is how cations are exchanged, but the amount of anion (SO4 ~) does not change.
Gradually, all exchangeable sodium passes from the clays into solution. Waters from sulfate calcium (magnesium) are transformed into sulfate sodium, and the absorbing complex from a typical marine - sodium becomes a typically continental - calcium-magnesium (A.I. Perelman, 1982).
The clay fraction of soils and rocks contains two categories of ions: some easily pass into solution and are capable of participating in reactions - these are exchangeable cations and anions; others are firmly fixed in the nodes of crystal lattices and can go into solution only as a result of the destruction of minerals during long-term weathering processes.
The impurities included in clay determine its color, consistency, special plasticity or rock hardness. There are up to 40 types of clays used in the earthenware and porcelain industries, pharmacology, construction, perfumery (the main part of powder), chemistry, and the food industry. Clay can be white, blue, gray, red, brown, green, black. Sometimes clays of chocolate or dirty black color are found.
The colors of clay are determined by the large amount of salts present in them:
Red color - potassium, iron;
Greenish - copper, ferrous iron;
Blue - cobalt, cadmium;
Dark brown and black - carbon, iron;
Yellow - sodium, ferric iron, sulfur and its salts.
Blue, green and black clay are considered the most active. Kaolinite has been well studied - the basis for porcelain products; it is white. Refractory clays are mainly kaolin, they are plastic, but they have little iron.
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- 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 the sale of 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.