double pelt (skin)- Ndp. sawing the hide (skin) splitting the skin (leather) Leveling the skin (leather) in thickness and separating it into several layers. [GOST 3123 78] Inadmissible, not recommended sawing of pelt (leather) spalling of pelt (leather) Topics leather ... ... Technical Translator's Handbook

The operation of leather production, which consists in dividing the semi-finished leather product by thickness into several (usually 2 3) layers. D. is performed in order to obtain skin of a certain uniform thickness. D. subjected to a semi-finished product, ... ... Great Soviet Encyclopedia

- (nervi craniales; synonym for cranial nerves) nerves extending from the brain or entering it. There are 12 pairs of C. n., which innervate the skin, muscles, glands (lacrimal and salivary) and other organs of the head and neck, as well as a number of organs ... ... Medical Encyclopedia

POISONING- POISONING. Poisoning is understood as “disorders of animal functions. organisms caused by exogenous or endogenous, chemically or physicochemically active substances, which are alien in terms of quality, quantity or concentration ... ...

I Examination of the patient Examination of the patient is a complex of studies aimed at identifying individual characteristics of the patient, establishing the diagnosis of the disease, substantiating rational treatment, determining the prognosis. The volume of research at O ​​... Medical Encyclopedia

I Poisoning (acute) Poisoning diseases that develop as a result of exogenous exposure to the human or animal body of chemical compounds in quantities that cause violations of physiological functions and endanger life. IN … Medical Encyclopedia

I Diffuse toxic goiter (struma diffusa toxica; synonym: Graves' disease, Graves' disease, diffuse thyrotoxic goiter, Parry's disease, Flayani's disease) is a disease of an autoimmune nature, which is based on a genetically determined ... ... Medical Encyclopedia

KIDNEYS- KIDNEYS. Contents: I. Anatomy of P .................... 65$ II. Histology P. . ................ 668 III. Comparative Physiology 11......... 675 IV. Pat. anatomy II ................ 680 V. Functional diagnostics 11 ........ 6 89 VI. Clinic P… Big Medical Encyclopedia

I Respiratory failure is a pathological condition in which the external respiration system does not provide normal blood gas composition, or it is provided only by increased work of breathing, manifested by shortness of breath. This is the definition... Medical Encyclopedia

- (vasa sanguifera, vaea sanguinea) form a closed system through which blood is transported from the heart to the periphery to all organs and tissues and back to the heart. Arteries carry blood away from the heart, and veins return blood to the heart. Medical Encyclopedia

DIABETES DIABETES- DIABETES DIABETES. Contents: Historical data...............50 General information and statistics.............51 Pat. anatomy ....... ..........53 Pathogenesis .....................55 Symptomatology and course of any ... .....57 Treatment......................60… … Big Medical Encyclopedia

Production genuine leather

The skin really High Quality stages of the technological cycle of its processing to the finished product should be the less, the better. The "face" of the hide (the top layer of the skin) should be completely preserved, if not emphasized. This means that the wrinkles and pores present on the skin that is being processed must be preserved.

LEATHER TECHNOLOGY

Leather production technology (processing of skins to finished leather) consists of three stages: skin preparation, leather tanning, leather finishing.

Canning skins

The skin preservation procedure is done in order to impregnate the skin with salts. Why do they do it? When an animal has been slaughtered, both its meat and skin immediately begin to deteriorate. When canning the skin, half of its moisture is lost, the skin is dried from three to six days. And only then the raw materials are sent to tanneries for further processing.

1. SKIN PREPARATION

Leather preparation is the washing off of dirt, the removal of hair from the skins - the initial stage of processing raw materials for the production of leather, after which the skin enters the tanning shop. The purpose of these procedures is to remove animal th wool and subcutaneous tissue, as well as prepare the skin for the second stage - tanning. At this stage, the skin with hair, which is called the dermis, turns into an untanned semi-finished product - naked. At the skin processing plant, the skin of the animal is treated with salts (sodium chloride and carbonate), and then the canned skin is dried. The leather is then processed using leather processing equipment.

Here, too, the following steps can be distinguished:

Soak off

Soaking hides: the skin should be soaked, washed with chemical solutions and water. The skins are cleaned of blood, dirt, preservative salts, fats, etc. This process lasts from eight to twenty hours (it all depends on how thick the skin is).

Gilding skins

Green in the process
Skinning is the removal of hair and epidermis from the skins produced. Gilding is the subjecting of an animal skin to a treatment with lime slurry. The gilding of the skin is necessary so that in the subsequent, further process processing the skins of the hair easily moved away from the skin, to achieve the necessary swelling of the skin fibers themselves.

Hair removal (hair removal)

Hair removal (hair removal) is done on machines, the name of which speaks for itself - hair removal machines.

The semi-finished product of the skin, after the wool is driven from it, becomes naked.

Mezdrenie

Skinning - this is the removal of the subcutaneous fat layer, excess pulp and muscles (mezdra) with the help of meat machines. The first skinning, as a rule, is done over the skin after it has been partially soaked, and the second skinning after the wool has been driven off. With poor-quality mezdreniya, such bad defects as snags appear on the skin.

Peeling face skins (peeling skins)

Cleansing the face of the skin is the removal of the remaining short hair from the skin.

Anesthesia

Deashing occurs to remove calcium compounds (salts) from the processed skin. If this is not done, then the skin turns out to be tough, which subsequently creates such defects as breaking the face and setting.

skin washing

The skin is washed with water. This procedure is carried out in order to finally remove calcium salts and protein breakdown products. After washing, the raw material (fine) goes to tanning.

But for a few individual types of leather, additional preparatory procedures are used:

Double skin

The double skin is produced in double skin machines. Doubling of the skin is usually produced when the hide has a rather increased
thickness. The need for doubling of the skin appears in the development of relatively thin leather intended for the top of shoe products.

Chepraking

Chepraking is the division of the produced skin into so-called topographical sections. Large skins are subjected to shaping.

Skin softening

Skin softening is the treatment of the skin with various enzymes (as a rule, these are pancreatic enzymes), under the influence of which the skin becomes softer, more viscous and smoother. Softening is used, as a rule, when producing leather for clothes, haberdashery leather and soft shoe leather.

Pickling

Pickling of skins implies the treatment of the hide with an acid-salt solution - a pickle. In the process of pickling the skins, the skin is additionally loosened, which leads to an increase in its softness. Picking is inherently skin preservation, so skins can be stored for a long time without spoiling.

2. tanning

Tanning is a process when the obtained skins are processed in special tanning drums, which results in a semi-finished product.

The purpose of tanning is to stabilize the hide, i.e. the skin should acquire elasticity, plasticity, and wear resistance. After tanning, the skin is used without any particular fear of damaging it.

3. LEATHER FINISH

Leather trim includes:

Skin coloring.

Skin coloring occurs with various dyes, which are obtained from oil.

Fat treatment of the skin.

After dyeing, the skin is treated with fat to make it softer.

After that, the skin is dried by stretching on special frames, which are later placed in a drying oven.

Kneading the skin gives it softness.

Rolling skin.

Skin ironing.

Skin pressing.

Leather embossing.

Applying lacquer to leather.

Grinding of the front surface.

Not often the front surface of the skin has a surface without scars, cuts, abrasions and other defects. In order to hide these defects, the skin is polished.

Applying wax to the skin.

Giving leather properties such as gloss, water resistance, dirt repellency, fire resistance, etc.

How to make skin video

Leather- This natural material made from the skins of various animals. Just as no two animals are the same, so there are no two identical pieces of skin. These natural features are not defects, but only add to the uniqueness of each finished product. This is especially true for exotic skins.

Leatherworking is perhaps one of the oldest crafts on earth. Primitive people began to process animal skins many thousands of years ago. This process can be called the very first manufacturing industry. According to archaeologists, the remains of leather clothes were found in ancient Egypt, which were made as early as the 13th century BC. Almost everything was made from leather. Ancient people used primitive shoes to protect their feet: they wrapped their feet with pieces of animal skins and fastened them with leather strips or veins. The very first human shoes were sandals, which instead of soles had a plank tied to the foot with leather straps.

Animals were hunted for their meat and fat, but the animal had to be skinned before food was used. For this, sharp pieces of flint were used, and later, flint knives. Further, the skins were used to warm the bodies of people and wrapped around the legs, representing the first type of boots. But raw skins soon began to decompose and rot. Drying the hides in the sun was observed to conserve them, but the result was a very hard, inflexible material, of little use for clothing. The skins needed to be softened. This was done by rubbing the hide to be prepared with various fats.

The fat also helped keep the hides from getting wet. This type of processing made animal skins soft and elastic. In addition, for the treatment of skins, water was used, to which different kinds bark and berries. It was found that after such treatment, the skins became significantly softer and could resist decay. Active substances contained in extracts from certain plants and producing such an effect on animal skins are called tannins. It was one of the first methods of tanning leather. Gradually, the technique of making things from leather improved, household items turned into real works of art.

Probably, all the peoples of the Earth were engaged in leatherworking, because in ancient times leather was the most accessible material. Humanity learned to spin and weave much later. The Ugrians (a group of Finnish peoples - the Finno-Ugric language group) sewed boots from the skin of birds with plumage; many tribes decorated leather clothes and shoes embroidered with silk and gold, precious stones, painting, pearls. The Indians closed the seams on leather clothing with strips of colored prickly fish scales so that the seams would not let moisture through.

For the Slavs, leatherworking was also the oldest craft. Already in the VI-VII centuries in Rus' were known various ways leather dressing and processing. Artistic processing of leather especially developed in the North and Central Russia. So, for example, in the city of Torzhok they made multi-colored morocco, made pillows, belts, purses, pouches, shoes embroidered with silver, gold, and silk from it. Before the First World War, these items were exported from Russia, as well as some types of leather, which were superior in quality to European counterparts.

Another thing to be noted is the widespread use of leather in book printing. For a long time, books were written on parchment - calfskin dried on a frame. In addition, book bindings themselves were made of leather.

The processes used to make leather today were invented by our ancestors many thousands of years ago. Since ancient times, leather has been made using the tanning process, which uses animal brains as a source of emulsified oils. This process is known as "Indian tanning" and the practice is still used by some people on a small scale. This tanning process is most often used for deer skins. This practice gave rise to the saying that "the animal has mental capacity, which is only enough to preserve his own skin, dead or alive.

The skin has not lost its relevance and modern world. With all the development of technology and the emergence of new synthetic materials- the skin continues to attract more and more new supporters and admirers. Nowadays, genuine leather products are in great demand, despite their high price.

PRODUCTION OF GENUINE LEATHER

Leather processing

It is believed that the highest quality leather is made from the skins of cows (ox, calf). It is used for shoes, clothing, furniture upholstery, etc. Leather from sheep or goat skins (sheepskin, goat skin) is mainly used with hairline (like fur). Pigskin leather is elastic, but has a persistent characteristic odor, which is why it is valued lower than others. Skin from crocodile, python, stingray, ostrich and other exotic animals is used for the production of leather goods, clothing, footwear and other business areas.

There is a rule that the higher the quality of the skin, the fewer stages in the technological cycle of its processing to the finished skin. The challenge when processing skins with a good face (by face is the top layer of the hide) is usually to keep the face intact and even emphasized. On the finished product, the natural pattern of the face is preserved - wrinkles and pores, which are present on the raw skin. Applying the palm to the surface of the skin with natural person(fool grain) you get the feeling of a natural elastic product.

The skins of dairy calves (calves), having a smaller thickness compared to the skins of adult animals, can compete with them in terms of strength and wear resistance. This is due to the denser and denser fiber structure of the skins of dairy calves. The process of processing skins to finished leather can be simplified as a combination of three main stages:

Leather dressing.

Dressing is one of the most simple ways leather processing, at the same time the most ancient of them.

The production of finished leather is a rather laborious and lengthy process, which consists of three main stages leather production:

soaking-ash processes;

preparatory processes and tanning;

chemical finishing and dyeing and greasing processes.

1. Washing-ash processes

Raw skins: skins of cattle, mainly skins of bulls and cows, taking into account their origin and weight category. Raw skins are supplied from the south of Germany and Switzerland, as well as from other regions: skins of wild animals - from the USA, South America, Australia, New Zealand, etc., in some cases, water buffalo skins are used (India and Indonesia), less often - calf and pork skins.

Canning: If the delivery of the skin does not take much time and its immediate processing is provided, then the skin is simply frozen. For all cases, the supply of salted skins is considered normal.

Soaking: First stage of processing. The skins are soaked to remove dirt. They re-hydrate. Biological moisturizers are used for softening. First, preliminary softness is achieved, then the main one. After the skin is softened, the remaining meat can be removed.

Gilding: Removal of the upper stratum corneum of the skin and hairline. At this stage, the type of leather is determined, which serves as the basis for its further intended use. The applied chem. substances: lime and sodium sulfide, which are then neutralized with acid.

There are 4 main goals for this:

1) weaken the connection of the hair and epidermis with the dermis;

2) to carry out partial saponification of fatty substances;

3) to achieve sufficient swelling of the skin fibers;

4) bring the skin to the chemical state necessary for tanning.

In addition, the conditions of gilding and ashing also affect such properties of the finished leather as tensile strength and moisture capacity. The strength of the skins subjected to the intense action of the ash pan is always less. This is due to the destruction of bonds in the main chain (intramolecular bonds) during such development.

The water resistance of the skins decreases with intensive treatment with an ash solution, which is associated with an increase in their porosity.

2. Preparatory process With.

Hair trim. It is produced on special hair-cutting machines. This operation is carried out after gilding, when the connection between the hair and the dermis is weakened. The semi-finished product after wool shearing is usually called pelt.

Mezdrenie: Removal of cuts of meat, tendons and subcutaneous fat layer (mesdra). Mezdra is used for the production of technical gelatin. Finished leathers are ready for tanning and are called “sheepskins”.

Face cleaning. This operation follows after mezdreniya. Cleaning consists in removing short hair (sagging), as well as partly the decay products of proteins and fats.

Deashing and pickling: The skin is cleansed of ashing products by means of neutralization, defermentation is carried out - pickling. The skin is treated thoroughly and becomes smoother. The green pelt is in a state of gluttony - strong swelling and contains a large amount of calcium compounds, both associated with collagen and deposited in the form of lime and lime salts.

Heaving: Serves as a preparation for the mineral tanning process. The hide is immersed in drums of brine and then treated with a weakly concentrated acid. The tannins added during this process cannot yet act actively, but evenly impregnate the skin.

Flushing. Washing is carried out with water to remove calcium salts and protein breakdown products. After washing, the fleece enters the tanning machines for tanning.

doublingWetblue: Doubling is subjected to the skin, obtained from large raw materials (bull-calf, bull-calf, bull-calf, etc.). When doubling, the fleece after gilding is sawn on splitting machines into two layers: the upper front layer and the lower bakhtarmy.

The fleece over the entire surface is cut in thickness into layers. The layer with traces of skin defects is cut evenly over the entire thickness. The remaining layers retain their natural thickness unevenness. The top layer is the future genuine leather / The lower layers after tanning are called splits. The top layer of leather used for the production of leather furniture is additionally gilded.

When sawing, they are set by the thickness of the front split, so it is obtained with the same thickness over the entire area. The upper split is usually used for the manufacture of more important parts of shoes, bahtarmyany for less important parts of shoes and haberdashery leather.

At the same time, it should be taken into account that the overall strength of splits is low compared to the original hide.

In addition to the above preparatory operations for some types of leather, doubling, shaping, softening, pickling are additionally used.

2. 2. Tanning

Tanning shop.

The resulting raw material is processed in special tanning drums, after which a wet blue semi-finished chrome product is obtained, which is ready for use.

The resulting nakedness is unsuitable for the manufacture of shoes and other products. When flooded, the fleece swells strongly, absorbing large amounts of moisture and greatly increasing in volume.

Drying of the hide is accompanied by a sharp decrease in its volume, gluing of its structural elements and a change in mechanical properties. Dried pelt becomes hard, horny and brittle. The fleece is not resistant to heat when wet, bacteria and enzymes. Thus, the form, stability of the material is lost. To get rid of these phenomena, the netting is tanned, that is, it is treated with tannins.

According to modern concepts, tanning is the process of bonding collagen molecules with tanning agent particles (cross-linking of molecules)

The skin obtained as a result of tanning differs from the skin in a whole range of properties:

♦moisture capacity decreases, as the ability to swell in water is lost;

♦ stiffness increases, because during tanning due to the formation of additional cross-links in the dermis, the mobility of skin collagen macromolecules is lost;

♦the strength of the structural elements of the track is increased. But it should be remembered that excessive tanning, on the contrary, reduces strength. This is explained by the fact that when tanning above a certain optimum, the strength decreases due to an increase in rigidity and a decrease in the ability to orient the structural elements of the skin;

♦increased elasticity and associated wear resistance;

♦ heat resistance increases. This is due to the increase in the number of cross chemical bonds and the welding temperature during tanning (Tcg);

♦porosity increases. This is due to the fact that tanning agents, penetrating (wedging) into the structure of the dermis, separate the elements of the structure and in the future this is fixed due to the formation of chemical cross-links;

♦ form stability increases. This is due to the fact that tanning agents, forming cross-links between collagen macromolecules, do not allow the dermis to swell and, moreover, do not allow them to come together and stick together;

♦increased chemical resistance. This is due to the fact that the functional groups of collagen in the dermis are blocked by tannins;

♦appearance improves;

♦ the thickness, area and angle of inclination of bundles of collagen fibers increase in the dermis after tanning. This already speaks of the economic efficiency of tanning and, in particular, the increase in the wear resistance of sole leathers.

The modern theory of tanning considers tanning as a process consisting of a number of physical and chemical phenomena and proceeding in two stages. The first stage is the diffusion of the tanning agent into the thickness of the skin, the second is the interaction of the tanning agent with collagen molecules. In this case, both processes occur simultaneously.

Tanning substances are classified into two groups:

1. Organic (tanides, aldehydes, fats).

2. Mineral (titanium, chromium, zirconium and aluminum compounds).

Basic tanning:

Chrome tanning is carried out with aqueous solutions of basic salts of trivalent chromium, which is not poisonous. Tannins penetrate deep into the skin, which helps to strengthen it and will not cause damage under normal use. Hexavalent chromium is not used for tanning, as it is poisonous. After the penetration of chromium into the treated skin, the acid residues are partially drawn out, and the chromium is fixed in the skin fibers and thus neutralized. Similarly, zirconium, aluminum and titanium tanning is carried out.

Plating and drying:

To set the tannins, the skin is laid out in layers and dried.

Folding (rolling):

Serves to even out the thickness of the skin.

Neutralization: The remaining acids in the skin are carefully neutralized with slaked lime. In subsequent processing steps, skin groups are established.

Final tanning: modification and development of leather properties using stronger tannins in combination with the main tanning. It can be combined with vegetable and/or synthetic tannins, with chromium and other minerals.

3. Chemical finishing and dye-greasing processes

At the final stage of chemical finishing, the following operations are performed:

retanning (chromium compounds, syntans, and other special agents are used); Dyeing: leathers are dyed in dye baths with permanent dyes that penetrate deep into the leather fibers. Only natural, non-toxic and environmentally friendly dyes are used. The paint penetrates deeply into the structure of the skin, fattening (fats, oils, emulsifiers, ammonia are used)

The end product of leather production is leather, i.e. the entire technological process of production is nothing more than the transformation of the skin into finished leather.

Vegetable (aldehyde) tanned leather is leather that is made using tanning bark (hence the name "tanning") and other ingredients obtained from plants, tree barks and similar sources. The result is an elastic material. Brown. The desired shade is achieved by varying the quantity and quality of the ingredients used and by selecting the color of the raw materials. Vegetable tanned leather is not waterproof. When exposed to moisture, it changes color, and if it absorbs liquid and then dries, it will decrease in size (“shrink”) and harden, become less elastic. In hot water, this type of leather “shrinks” strongly and becomes a hard, brittle material, which limits its use.

Alum-tanned leather, in the course of which aluminum salts are used, mixed with various binders and protein substances, for example, egg powder, etc. Purists argue that alum-tanned leather is technically rawhide, not tanned, as the resulting material will rot in water. As a result of using this process unsaturated tones are obtained, but the resulting material is not as elastic as vegetable tanned leather.

Rawhide is made by scraping the hide, soaking it in lime, and then stretching it while drying. Like alum-tanned leather, rawhide is not technically a "leather" but is usually referred to along with other forms of leather. Rawhide is tougher and more brittle than other forms of leather and is used to make drums, as well as cords used for lacing or stitching.

Boiled leather - leather products (vegetable tanned leather), to increase strength, are immersed in hot water or into boiling wax, or similar substances. Historically, such leather was used as armor due to its hardness and light weight, and was also used for book bindings.

Chrome-tanned leather, invented in 1858, uses chromium sulfate and other chromium salts to make leather. This form of leather is softer and more elastic than vegetable tanned leather. In addition, it does not change color and does not lose shape when exposed to water, like vegetable tanned leather.

Leather (usually vegetable tanned leather) can be lubricated with certain oily substances to improve its water resistance. This increases the amount of natural fats found directly in the skin, which are washed out during the operation of leather products, which can be exposed to intense moisture. Frequent lubrication of leather products with mink oil, refined oil or similar substances will keep the leather soft and prolong the life of the product.

Finished leather production.

The production of finished leather is a rather laborious and lengthy process that takes place in several stages.

Skin coloring.

The sorted leather is transferred to the dyeing shop, where the so-called Crust semi-finished product is obtained.

The semi-finished product is sorted and transferred for further coloring, which is carried out according to the latest technologies in special dyeing drums, which makes it possible to economically use chemistry and treat the leather delicately.

Before dyeing, the color of the skin depends on the tanning method (fat tanning - mustard yellow; chrome - light green color; iron - canary color, etc.).

Skins that do not have any defects, without spots and without masks, can be stained in various cysts; skin with spots turns black. For black coloration of the skin, after tanning and washing, it is dyed, then fattened and dried. For color dyeing, the skin is only dyed without being fattened, since the fat can leave stains.

Used for black dyeing vegetable paints and aniline dyes; for colored leathers, aniline dyes are now almost exclusively used.

Aniline dyes are divided into basic and acidic.

Perfectly smooth elite leather at this stage is ready to go to the packaging shop.

Leather, which for one reason or another is not smooth, is embossed.

Experts determine the quality of the leather and the type of embossing that will help hide minor imperfections in the surface of the leather.

A variety of types of embossing are used: from very small (the so-called pulverized plate) to very large (the so-called Tigina), as well as shagreen embossing, used for tailoring shoes for special purposes.

fine embossing

shagreen embossing

very fine embossing

very large embossing

large embossing

medium embossing

Before packing and sending to the warehouse of finished products, all leather undergoes final sorting and measurement.

When the skins, after the preservation process, reach the tannery, they are examined for signs of damage or poorly prepared and preserved hides. At this stage, the entire batch of skins can be rejected and returned to the manufacturer.

In turn, the skin is classified according to the method of coloring:

1. Immersion coloring. Fold two skins with the inside and immerse manually in 40-50° dye bath; while the inner side is painted only very weakly. This method is used for dyeing small leathers (goats, sheep, calves, etc.), with a small amount of them.

2. Painting in a vat with wide rotating blades. The blades, when rotated together with the dyeing bath, turn and skin. With this method, which is especially suitable for large quantities of leathers, both sides of the leather are dyed.

3. Coloring in the washing drum, closed rotating vessel with hollow axes for adding the coloring solution. This method requires a very "short" dye bath, so that dyes can be used very well; this method is mainly used for chrome leather.

4. Applying paint with brushes produced mostly on large skins. The skin is spread on the table, the upper side is well wetted, and then the paint is applied.

5. Coloring substances. For dyeing leather tanned with vegetable oak substances, basic and acid dyes are used, less often substantive ones. When using basic dyes, add 1-2 g of acetic acid per 1 liter of dye mixture. For acid dyes, add 1-3 g of formic acid per 1 liter of water. Nothing is added to substantive dyes. In all cases, coloring is done at 45-50°.

6. Chrome leather finish. For chrome skin, acidic dyes are primarily used with the addition of acetic or sulfuric acid. Before adding the coloring matter, for better fixing of the color, the skin should be treated with quebracho extract. Basic dyes are also suitable for coloring chrome leather; the quebracho bath is enhanced accordingly. Acetic acid should be added to substantive dyes. The temperature of the dye baths can reach up to 50-60°.

7. Coloring of kid skin. Laika skin is dyed like chrome, but the temperature of the dye baths should be lower (40-45 °).

(Mainly acidic and basic dyes are used.)

8. Suede leather finish. When dyeing suede, basic paints are used (with Glauber's salt and acetic acid) and dyed at a temperature of 30 °. Acid dyes are used with the addition of Glauber's salt, at a dye bath temperature of 40-45 °.

9. Patent leather finish. a) In black. The skin to be lacquered is fixed in a frame, placed on a smooth board and front side polished with a piece of pumice stone until the skin is no longer rough. Next, they take a good oil varnish, mix it with Dutch soot and make a liquid paint from this, with which they smear the skin; then the latter is exposed to the sun to dry, and carefully protected from dust.

Having done this, they proceed as before, dry again, take pumice and polish; when the skin becomes smooth, it is dried for an hour, after which the paint that was applied is mixed with Dutch soot and smeared with liquid 2-3 more times.

When it dries again, take felt and finely ground pumice stone and polish until the skin is completely smooth.

Skin Configuration

In production, leather is cut and has various configurations.

Scraping is the division of the skin into topographic sections. Scraping is subjected to large raw materials, the topographic sections of which are most differentiated in thickness and microstructure.

According to the configuration of the skin there are: whole skin, semi-skin, kulat, semi-kulat, collar, saddle.

Types of leather according to the method of finishing

Smooth skins

They preserve the natural pattern as much as possible - measure, are not embossed at all, or a very small - "dust-like" embossing is applied to the front surface. The skins of this group are made from the highest quality raw materials using the most modern chemical materials.

Sanded leather

Grinding the fringed side and additional splitting make it possible to obtain "Velour", which is used for the production of sports, home and model shoes. However, there are leathers, the polishing of which is predetermined by the technology of their dressing - this is "Nubuk", which is indispensable for the manufacture of both men's and women's shoes. Colored nubuck inserts are widely used in the production of children's shoes.

Embossed leather

Leathers of the middle and lower price ranges are indispensable for inexpensive, work or uniform shoes. They differ in pattern and embossing depth. The finer the pattern and the depth of embossing, the less ability to hide defects this embossing has. All drawings can be divided into several categories:

Patent leather

Depending on the properties and color of the coating, the skin can acquire a wide variety of color and organoleptic properties. Such leather is very widely used in the production of both women's and men's model shoes. Patent leathers are represented by the articles "Orion", "Naplak". Patent leather can be embossed to obtain the desired pattern. Patent leather shoes look great and always attract attention.

splits

An artificial polymer "face" is applied to the split leather, imitating the natural front surface. The split leather production technology allows using inexpensive raw materials and obtaining an excellent solution for the production of inexpensive shoes with a quality close to the quality of genuine leather with a grain surface. The range of splits with an artificial front surface is represented by the article "Legend" with various options embossing. All options for embossing splits are identical to embossing leather with a front cover, which allows you to combine them in the production of shoes (toe - front leather, ankle boots, tops - split). Split splits without applying an artificial "face" are used for the manufacture of shoe lining material, sewing overalls.

Krasty

Semi-finished leather obtained after a drum-dyeing operation (no surface finish). It has a natural face pattern. The lack of surface finish avoids most of the flaws associated with exfoliation of the "face" - wrinkling and fragrance. Modern processing allows to give the crust the property of hydrophobicity, and special dyeing - through paint. A well-dressed crust is difficult to distinguish from leathers with a smooth grain. Crusts are widely used by shoemakers for the production of shoes for a wide variety of purposes.

Leather substitutes.

We distinguish 4 main types of products we represent (3 types of artificial leather and PVC film):

Iskozha (leatherette) MF. This is a modern skin based on microfibers (Micro Fiber)

Iskozha (leatherette) PU. This modern type faux polyurethane leather

Iskozha (leatherette) PVC. Classic PVC leather

PVC film. PVC film

Today, artificial leather(leatherette), is a high-quality and environmentally friendly material that surpasses natural leather in some respects. At the request of the customer, in terms of aesthetic appearance, artificial leather is no different from natural leather, both from the front and back sides. At the same time, it is possible to make artificial leather with a texture and color that is not characteristic of natural leather, which designers skillfully embody in their fashionable modern projects.

Nowadays, most types of leather are made from cow hides, but skins from other animals are also used. The skins of lambs and deer are used to produce soft leather, from which the most expensive clothes are sewn. Kangaroo skin is used as a raw material for the production of products that must be strong but flexible, such as leggings. Leather made from the skins of more exotic animals, in particular some types of reptiles, was very popular at one time. Products from it were considered the most beautiful and refined. For this reason, the hunting of certain species of snakes and crocodiles has become so widespread that it has put the above species of reptiles and cold-blooded animals on the brink of extinction.

Leather production process

British Standard BS 2780 Definition of leather:

“The general term for a material that has come from the skin of an animal and retains the structure of the fibers of this skin more or less unchanged, tanned to stop the processes of decay. Fur and hair can be removed or left on the surface of the skin. No product can be called "leather" if during its production the original fiber structure of the animal skin is destroyed and processed into separate loose fibers and/or powder and/or other fragments by any chemical and/or mechanical method, followed by the reconstruction of these fragments into flat materials and/or other forms. If the skin has an outer coating, its thickness should not exceed 0.15 mm.

The process of turning raw hide into leather is not an easy task, and in fact consists of a chain of successive actions. These actions can be divided into four related groups, namely:

• Preparatory work in the tannery
• Tanning
• Retanning
• Finishing

Preparatory work in the tannery

The main purpose of the preparatory work is to completely clean the skin of various unwanted components, such as wool or hair, unstructured proteins and flesh residues.

Soaking (soaking). During soaking, dirt and blood residues are removed from the surface of the skin. To avoid shrinkage of the skin during the soaking process, the water temperature is maintained at 20°C. Sometimes, for better purification, they add to the water detergents containing alkali; among other things, alkali allows the skin to absorb moisture more intensively. Moisturizing the hide is an important part of the soaking process.

Dehairing and ashing. At this stage, the skins are again soaked in an alkaline environment. This allows you to get rid of hairs, soften collagen fibers and destroy unstructured proteins (if they are not removed in time, the skin will turn out to be too hard).

Mezdrenie. In the process of skinning, pre-washed skins are passed through a special apparatus that removes unnecessary remnants of flesh, connective tissue and fat.

Doubling. Now the skin can be divided into two parts (more precisely, layers). The top (outer) layer of leather resulting from doubling is widely used in the leather industry and as frontal upholstery, as it contains a layer of grain, the pattern of which can then be preserved, corrected or embossed. The bottom layer (the so-called split) is used for the production of suede, as well as protected and pigmented leather. Split leather is often used when upholstering the back or side of a product.

Anesthesia. The task of the next stage is to reduce the amount of swollen and hard fibers. To do this, the existing alkaline environment is neutralized with acid-containing substances, such as chloride or ammonium sulfate.

Softening. This process makes the hide smoother and flatter, emphasizing its texture. In addition, it is thanks to him that the skin becomes softer and more elastic.

Pickling. The last stage of preparation for tanning. To reduce the pH (pH) of the material, it is again treated with acid (sometimes along with salt to prevent the skin from swelling too much).

Tanning

Almost everyone knows about this procedure. And this is not surprising, because leather tanning is one of the most milestones during its processing. Have not forgotten the strict scientific definition? According to him, the skin, not touched by tanning, cannot yet be considered skin as such. As a result of tanning, the collagen proteins contained in the skin become a strong material that is difficult to decompose and resistant to heat and moisture.

Mankind has invented many ways of tanning leather. The most popular in the leather business and, perhaps, the only one that it will be useful for you to hear about is the so-called wet blue (from the English wet blue: wet and blue) or “chrome tanning”. This term is applied to leather that has been tanned with chromium salts. But why "wet and blue"? The answer is obscenely simple - the resulting material is really wet and has a bluish tint.

Skin processing takes place in large barrels (usually such a barrel can hold up to three hundred skins at a time). Chromium reacts with the collagens contained in the skin and colors them in Blue colour. The tanning process is considered to be fully completed when the skin becomes resistant to high temperatures and does not shrink at 100°C. The advantages of this method include the high strength of the resulting material, as well as its resistance to heat and light. That is why chromium tanning is the most common and popular way of leather tanning today.

The final stage of tanning is to remove excess moisture from the skin. To do this, the skin is passed through a special apparatus equipped with felt pads, which squeeze out all the excess fluid.

Retanning

Neutralization. To prepare the skin for a chain of further chemical processes, it is treated with a weak solution of alkali.

Coloring. This step does not need further explanation. The skin is also dyed in barrels, most often using anionic dyes - they are negatively charged, and therefore they bond well with the previously “chromed” skin.

Fattening. To lubricate the fibers of the skin and make them softer, special fats and oils are used. They penetrate the skin, filling all its pores. By the way, it is at this moment that the skin acquires its own unique smell!

Drying. The skin is hung on poles, or laid out on special boards, and then dried with a stream of warm air. The latter method is especially popular, because it takes only a few minutes to dry one skin!

breakdown. At this stage, the skin becomes softer. It is passed through a series of special blunt pins that beat and wrinkle the skin, thereby softening it.

Finishing

Finishing is a process that consists in processing finished leather and applying various coatings to its surface. The advantages of covered (or "protected") skin include:

• Greater durability
• Ease of care and maintenance
• Improved water repellency
• Masking natural defects
• Attractive color and appearance

Three processes can be attributed directly to leather finishing: grinding, coating and embossing. Depending on the type of skin, some (or even all) of these activities may be excluded.

Grinding. If the upper porous surface of the leather is in good condition, then the leather is not processed at all - the so-called coarse-grained (full grain) leather is obtained. In the upholstery business, it is highly valued, and in fact only a very small percentage of the hides are good enough to go into the production of full-grain leather.

Most often, the skin (for example, cow) bears traces of scratches, bites or cuts received by the animal during its lifetime. All these defects, of course, negatively affect the texture and need to be corrected. A special liquid filler (“skin repair composition”) is applied to the damaged areas. Then the skin is dried and its porous part is processed with a special grinder with abrasive material in order to completely hide the existing imperfections. This type of leather is known as corrected grain or fine-faced leather.

Grinding also serves another additional purpose - it prepares the skin for subsequent pigmentation, providing better penetration and fixing of the pigment.

Coating. Corrected leather pigmentation is applied to give the material the correct uniform color. The concentrated pigment itself does not stick to the skin, it needs a base, which is most often used as acrylic or some kind of solvent containing substances that provide adhesion.

To fix the color, varnishing is carried out after applying the pigment. The lacquer protects the leather and makes it more durable, but not only - it is with the help of the lacquer that the necessary degree of gloss of leather products is achieved.

There are three ways to apply pigment to the skin.

1. Manual spraying with an airbrush
2. Automatic spraying on conveyor belt
3. Pressing paint with rollers. Very often, the second and third methods are used together.

Varnishes are applied by airbrush, manually or on a conveyor.

Embossing. After coating, the grain pattern can be changed artificially. To do this, a special metal mold with a pattern applied to it is applied to the upper layer of the skin. When enough high temperature it is pressed with force into the surface of the skin, giving it the desired relief. And sometimes the skin is passed through rollers, on which an artificial relief pattern is applied.

This is, in the most general terms, the path that the skin goes from a raw, unprocessed skin to a finished product familiar to all of us.

For the production of leather bags, leather obtained from the skins of cattle (cattle) as well as leather obtained from the skins of sheep is mainly used. For modern leathers appearance Manufacturers use various technologies for finishing the front layer of leather, which makes it possible to achieve a wide variety in the range of leather products.

patent leather
chrome-tanned leather with lacquer coating (duplicated with lacquer film)

Cattle skin
(cattle) with acrylic coating. Finishing the skin with acrylic emulsions to form a transparent shiny film.

Nappa
thin skin increased elasticity, made from cattle skins.

Napplac
lacquered nappa.

Velours
chrome-tanned leather with a sanded front surface or bakhtarma. A tanned semi-finished product with deep facial defects, unsuitable for the production of leather with a natural front surface, is selected and processed to look like velor.

Skin with a refined front surface
skin from which the front layer has been mechanically removed and an artificial layer of polymer has been applied.

chevret
chrome-tanned sheepskin leather.

split
part of the skin (skin) obtained after doubling. Distinguish front and bahtarmy split.

Facial split
part of the skin after doubling in which the facial layer (upper part of the skin) is preserved.

Bahtarmy split
part of the skin after doubling in which the bakhtarma (lower part of the skin) is preserved.

bakhtarma
the underside of a tanned animal skin.

Double skin
smoothing the skin in thickness and dividing into several layers.

Mereya
natural pattern on the skin. On the skin different types Animals are distinguished by a measure characteristic only for a given species of animals.

Face slicing (slicing skin)
drawing patterns on the front surface of the skin, sometimes imitating the measure of various animals. It is carried out with a hot plate. For example: the production of leather with a pattern of a deer, an ostrich, a crocodile, etc.

Nubuck
fleecy chrome-tanned leather with a front surface polished with a fine-grained abrasive material.

Leather painted with imitation painting
exclusive finishing of the front layer of the skin, which consists in painting the skin with paints or printing a picture both manually and with the help of special equipment.

Leather furniture - types of leather

Furniture made of leather is stylish and practical. There are 4 categories of leather:

Category A. Semi-aniline, fully adjusted. It has many flaws and therefore undergoes the most thorough processing: irregularities are puttied with a special composition, the skin is dried, polished. Then pigmented and sanded again. After that, the skin is covered with a polymer that protects it from the adherence of dirt and dust, and a relief is applied to it with rollers. This is the easiest and most durable type of leather to take care of.

Category B. Partially corrected aniline and semi-aniline leather. The processing method is similar to the above for category A leather. This category is more expensive than the first, since the properties are close to category C.

Grade C. Aniline, all natural finish. Such leathers, which have a natural top layer, are especially comfortable to use, as they are able to adapt to any temperature, "breathe" and maintain heat exchange between human skin and the environment.

Category S. Unlike C, category S leathers have an artificial upper layer and a high-quality sheep or calf inner layer. The properties of this skin allow you to give it any color, and apply any pattern on it.