One of the most valuable materials for making high-quality leather is the skin of a cow. Beautiful stylish clothes, shoes, accessories, bags, belts, furniture upholstery are made from it. The correct dressing procedure results in soft, smooth leather that does not crack or break. Its products are durable and long lasting. These products retain their visual appeal for many years, without losing their relevance in the cycle of the latest trends in modern fashion.

Varieties of calfskin

The skin of a young bull, calf is the most valuable raw material for the production of high quality products. Depending on the age of the animal, the qualitative characteristics of such material have their own characteristics.

Even calves that have not yet been born serve as a source of skin for humans. It is called "sklizok" and has a thickness of 1 to 1.4 mm. The most valuable material, which is distinguished by its softness, tenderness, elasticity, is the “calf box”. This is the skin of young cattle up to six months, who are breastfed. Its thickness is 0.5-1.4 mm. “Growth”, “half-skin”, respectively, are supplied by adolescent cattle under the age of 1 and 1.5 years. This material is more rigid and thicker (up to 3 mm). "Yalovka", "bull" - the skin of a young cow (4 mm) and a bull (5 mm), which must be sawn in accordance with proven technology.

A properly dressed calf skin is of particular value. To correct the source material, a careful approach to the study of processing technology and accuracy is required.

What is animal skin for?

Leather production has a rich history and traditions. Since ancient times, man has learned to dress the skin of animals at home. The resulting material served as the basis for the production of shoes, clothes, bags, belts, and later, unique accessories.

Genuine cowhide can be classified according to the purpose and method of finishing. Its thickest version, characterized by increased strength, wear resistance, is used for shoes, horse equipment, belts. The softer material is ideal for clothing and bags.

In accordance with the method of processing and coloring, cattle skins are divided into several types, which are called differently. They will be discussed below. At the same time, this taxonomy takes into account skin areas on the body of an animal that are used for leather production.

Classification by type and method of processing the skin

Aniline leather is the highest quality variety of this material. It is obtained in the process of dyeing with organic dyes with minimal processing.

"Bull" is the skin of a bull, which is best suited for manual, mechanical stamping. Such a durable material with a thickness of up to 5 mm can be used for a very long time, while maintaining its visual appeal and properties.

"Nappa" is a semi-aniline material of high quality, it is particularly elastic and soft. Its variety is considered "Napplak", which is obtained by applying varnish.

"Chopper" is a dense heavy thick skin. For its manufacture by the method of fat tanning, the skin of cows from the back is used. A more plastic version of it will be called "Shora".

"Yuft" is obtained from the skin taken from the abdominal region of adult animals. In the process of fat tanning, after washing, skinning, trampling, kneading, cutting and a number of other operations, a thick, but plastic and soft material is obtained.

Preparation of harvested skins for dressing

The harvested skin of a cow must meet certain requirements, so strict rules of technology should be followed from the very beginning.

The technological scheme for canning cattle skins by the dry method consists of the following important points:

• cleaning from the remnants of fat and meat;
• cooling the material on a flat surface in a straightened form with the fur down;
• abundant application of table salt without iodine content;
• drying the skin for several days until it becomes dry and hard.

After that, dressing at home should be preceded by sorting. This creates conditions for long-term storage. In addition, the size, thickness of the skin layer and the weight of the material are taken into account. This allows you to accurately calculate the amount of required reagents that will be used in processing.

Leather dressing at home

The skin of a cow is processed by hand without much difficulty. There are many ways to make leather. A method based on the use of sour milk has become widespread. The skins pre-soaked in clean cold water must be rubbed with coarse salt. Then wet-salted pieces should be folded into piles with the flesh down and kept for three days. After that, you need to carefully remove the salt, wring out, wring out, skin the material. Put it in a container with one liter of sour milk with the outer side down for three days, stirring the milk occasionally.

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At the end of this process, washing, tanning, and fatliquoring are carried out.

Dressing skins at home requires effort and certain skills, so the first time it is rarely possible to achieve an excellent result.

Over time, with the development of individual operations, the overall quality of the work done by oneself improves.

Soaking and skinning of cattle skins

To make the skin of cattle soft, it should be soaked sequentially in two stages. First in clean water for four hours, and then keep twelve hours in an aqueous solution of salt. To prepare such a mixture, 20 g of salt per 1 liter of water is required. For 1 kg of skin you need 8 liters of solution.

After such treatment, in wet-salted pieces of skin, the subcutaneous layer should be easily removed. If there is no such effect, then the soaking time must be increased. To prevent a bacterial infection, furatsilin is used in the amount of 6 tablets per 10 liters of water.

Skinning refers to the process of removing the fat layer located under the skin of an animal. Such work can be done manually or with the help of a special device in the form of a rotating round knife. This procedure should be carried out carefully, since the hair follicles in the thickness of the skin can be severely damaged due to poor-quality cutting. You need to start from the tail and cut off the fat layer evenly from the axial center to the periphery.

Washing, pickling and pickling

The next stages after skinning are called washing and pickling.

The skin of a cow is thoroughly washed with warm water using detergents. To do this, it is best to use a solution in which 10 g of laundry soap, and sometimes soda ash, are dissolved in 1 liter of water.

To change the structure of the skin, the skins are placed inside a solution consisting of water, acetic acid - 0.15% and sodium chloride - 0.04%. In this case, the entire mass should be periodically mixed for 12 hours. When a white streak appears on the fold of the material when squeezing, it is ready.

Pickling can be replaced by pickling inside an aqueous solution of barley or oatmeal. To prepare it, you need to add an infused solution to heated water, which is prepared from a liter of water, 60 g of salt and 100 g of flour. The fermentation process requires constant monitoring, since it is impossible to overexpose the material inside the solution.

Tanning procedure

The skin of a cow is tanned to increase resistance to chemicals. A solution prepared from 1.5 g of chromium oxide dissolved in a liter of warm water is used. The material should be placed inside the solution for 6 hours and stirred occasionally.

At home, you can use chopped oak bark, nettle, willow branches, alder in the amount of 250 g, which is dissolved in one liter of water with 60 g of salt, and then boiled for half an hour and filtered. Animal skins are placed inside the solution for 6 hours.

Fattening

This process requires a special emulsion, which is prepared according to the following recipe.

In water heated to medium temperature, dissolve 200 g of laundry soap shavings, 10 g of ammonia and 80 g of any fat. With this composition, it is necessary to evenly process the mezdrovo layer of the skin. To do this, use a soft swab or brush. After this procedure, the skin must be kept in piles throughout the day.

Thus, the knowledge of how to dress the skin of cattle correctly is available to any person. Strict adherence to the rules of technology, accuracy, conscientious work will bring consistently good results.

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According to GOST 1134-73 all types leather raw materials depending on the quality are divided into four groups and four grades.

• 1st group - slime and calf, regardless of weight, foal weighing up to 5 kg inclusive, sheepskin and goat skin of all sizes, pork skins with an area of ​​30 to 70 dm 2 .
• 2nd group - outgrowth, skins of camels, horses, donkeys and mules weighing up to 10 kg, skins of pigs with an area of ​​70-120 dm 2, croupons of pork skins with an area of ​​30-50 dm 2.
• 3rd group - skins of cattle, horses, camels, donkeys, mules, buffaloes, yaks and elks weighing 10-17 kg inclusive, front and haz, halves of camel skins regardless of weight, skins of pigs with an area of ​​120-200 dm 2, croups of pork skins with an area of ​​over 50 dm 2 .
• 4th group - skins of cattle, horses, camels, donkeys, mules, buffaloes, yaks and elks weighing over 17 kg; skins of pigs with an area of ​​over 200 dm 2 .

Depending on the quality, the skins are divided into grades (I-IV). The grade is determined depending on the number of defects and their location on the skin. Three defects on the edge are equal to one in the middle of the skin. The useful area is considered to be a skin area not damaged by defects. Vices are evaluated by a certain number of units.

Skins that do not meet the requirements of grade IV are classified as a flap. It also includes skins that were used in everyday life, shaly, lumpy fresh-dry, keratinized, heavily smoky, as well as halves and pieces of small skins.

GOST 382-91 defines the purpose of raw hides for the production of various types of leather and the conditions for its delivery to tanneries.

The main types of leather raw materials. Leather raw materials are divided into small, large and pork. petty raw materials - skins of calves of cattle (sklizok, caldron, outgrowth), camels, foals (sklizok, foal, markup), sheep (Russian sheepskin, steppe sheepskin; according to the condition of the coat - woolen sheepskin, half-woolen, bean), goats (goat steppe, grain, skins of wild goats).

large raw materials - skins of cattle (half-skin, bull-calf, bull-calf, bull, yalovka, buffalo, yak, elk), horses (horse-skin, front, haz), camels (skins of adult camels, camels), donkeys, mules and animals other species (walrus, deer).

pork raw materials - pork skins, skins of boars. The suitability of raw materials for the production of high-grade leathers is determined by the thickness, uniformity in area, mass, density, ratio of the papillary and reticular layers of the dermis, chemical composition and the presence of defects.

The thickness of the skin determines its purpose for the production of one or another type of skin and the consumption of steam raw materials per 100 m 2

skin. The uniformity of the thickness of the skin over the area determines the cutting properties of the skin. The area of ​​the skin is also related to the cutting properties of the skin. Processing skins with an area of ​​​​less than 20 dm 2 is unprofitable.

The duration of their treatment with chemical solutions and the strength of the skin depend on the density of the skins.

The ratio of the papillary and reticular layers of the dermis is important, since the papillary layer determines the softness, and the reticular layer determines the tensile strength of the skin. The nature of the interweaving of the fibers of the dermis (angle of inclination, laying density) determines the physical and mechanical properties of the skin (tensile strength, abrasion, etc.).

The mass or area is determined for each skin separately. The mass of paired skins is determined after their cooling and ritual (contouring).

The output rates of the edge sections of the skin after its contouring at a moisture content of 67% are: for light bullock and medium cowhide - 7.4%, for bullock and heavy bullock - 7.3% of the weight of the pair skin.

The area of ​​sheepskin and goatskin is determined by multiplying the length of the skin from the upper edge of the neck to the base of the tail by its width along a line 3-4 cm below the cavities of the front paws. When determining the area of ​​the skins of pigs, the length of the skin is measured from the upper edge of the neck to the tangent line to the cavities of the hind legs, and the width - along the line 8-10 cm below the cavities of the front paws.

The thickness of the skin decreases from the rump to the collar and from the ridge to the floors. This decrease in thickness is called taper.

The thickness is determined at two points: one of them is located on the right side of the skin in the lower part of the saddle; the second determines the taper and is located on the same side of the skin, but in the upper part of the saddle.

The dressing of cattle skins is a complex process. High-quality leather is obtained from dressed cattle skins, from which clothes, shoes, bags, belts, furniture upholstery are sewn. Products are strong and durable.

After removing the skin from the animal, they begin to preserve it so that it can be stored and transported longer. You can save skins from damage in the following way.

1. First, clean from dirt, blood, fat and meat deposits, and then quickly dry in the air, hanging the skin on poles. When dried, the development of putrefactive bacteria in the skin stops. This method of preservation is practiced in warm weather and in the absence of salt.
2. The cleaned skin is laid out on a clean floor with the hair down and the mezra is sprinkled with a thick layer of salt. Salt can be rubbed into the skin. The skin is folded into an envelope and salted for two days in a cool place. At the end of the process, the skin is hung out on poles in the air to dry.
3. The skin can be preserved for a month in a wet-salty state, sprinkling the mezra with a thick layer of salt, the ends of the skin must be wrapped so that the brine does not flow out.

It is very difficult to dress cattle skins at home due to their large size and weight (15-25 kg). All processes must be mechanized; for water operations, a mechanical longboat or a converted domestic concrete mixer is needed. To facilitate the work, you can cut a large skin into 4 parts or into two parts along the ridge. All dressing work is carried out in a special warm room equipped with containers for processing skins, fixtures, tables and cabinets for tools and chemicals. The room must be equipped with an exhaust hood, plumbing and draining of the waste liquid.

Soaking skins

In order to obtain high-quality leather, raw materials must be properly soaked. The skins must be washed with chemical solutions and water, cleaned of blood, dirt, preservatives, fats. Mezdra should be close to the paired state over the entire area of ​​​​the skin. Soaking is carried out in two stages.

At the first stage, washing is carried out using surfactants for 3-4 hours. The temperature of the solution is 25 degrees. The LCD for a longboat is 5. The skins are loaded into the longboat in the evening.

The composition of the solution: salt 20 g / l, any antiseptic: formalin or KFN (sodium silicate fluoride) - 1 g / l. Washing powder or liquid soap - 2 g / l. The skins are stirred for 10 minutes every hour. At the end of washing, the dirty solution is drained and a new solution is prepared for soaking. The skins are loaded, mixed and left overnight.

The composition of the solution: LC = 5, temperature 35 degrees. The soaking time for different canning methods is different. Wet-salted method of preservation 2-4 hours, dry-salted - 8-12 hours, fresh-dry - 24 hours. In the morning, the skins are pulled out, spread on the goats to drain the liquid. The spent liquid is drained.

Mezdrenie 1

Skinning is carried out to remove the remnants of meat and fat on the dermis with the help of or manually on the deck with a two-handed dead end. It is necessary to work with a dead end carefully to prevent cuts and snatches of the skin.

gilding

To obtain high-quality skin from cattle skins, you need to remove the hairline. To do this, carry out the ashing of the skin.

When greening with lime and sodium sulfate, the hairline with the dermis is weakened and the skin swells. Collagen fibers are loosened, interfiber proteins are dissolved, the epidermis is destroyed, the skin enters into alkaline fat. The skin absorbs water, swells, becomes elastic. The time the skin is in the ash pan affects the softness. To obtain thick leather for the soles of shoes, the time spent in the ash pan is not significant, but for the leather of the uppers of shoes and clothes, the time is calculated in several days. Depending on the type, thickness and purpose of the leather, the time ranges from one to eight days.

Lime slaking is carried out in a separate container for 3 liters of water, 1 kg of quicklime until a suspension is formed in the form of liquid sour cream. The consumption for one fourth of the skin of cattle is 40 g of sodium sulfide and 160 g of lime. The skins are laid out in containers, poured with an ash solution, once a day the skins are shifted and the weakening of the hair in the bulbs is monitored. As soon as this moment is determined, they begin to remove the hairline.

Hair trim

Hair removal in small workshops is carried out on tables using wooden scrapers or on decks using two-handed scrapers; in large industries, dehairing is carried out on wool machines.

The skins are laid out on the tables with the hair up and the hair is removed with the help of wooden scrapers. After such an operation, the semi-finished product is called naked.

After removing the hair, the skins are again laid out in a sulfide-lime ash pan, for each skin, the time the hide is in the ash solution is different. As a result of gilding, an elastic swollen pelt is obtained, freed from wool, from proteins and non-protein components. The properties of the skin are significantly affected by the time the hide is in the ash pan, as a result of which the strength, porosity, plasticity, breathability, softness and rigidity of the leather change. At the end of the gilding process, the face and bakhtarma are cleaned.

Mezdrenie 2

A second skinning is done on the deck, the skins are laid out face down and the bakhtarma is cleaned with a two-handed scraper.

Face cleaning

The face of the skin also needs to be cleaned. Unwashed proteins, lime, sodium sulfide, the remains of hair follicles remain in the thickness of the skin, they need to be squeezed out, otherwise it will be difficult to rinse. The skins are laid face up on the tables and with plastic spatulas the face of the hide is cleaned with movements from the middle to the edges. Then carry out the weighing of the hide.

flushing

After chaffing, the rind is washed. The skins are immersed in a longboat or concrete mixer and washed several times to clean water with continuous stirring. First, they are washed in water at 25 - 28 degrees, and then in water at 18 - 20 degrees. During the washing process, the remains of the ash liquid are removed from the skin, the skin becomes denser, becomes thinner and not so slippery. Then the waste water is drained, the skins are allowed to drain right in the longboat.

Anesthesia

When anesthetized, the remains of calcium salts from the skin are removed and neutralized, fat is removed, which helps to eliminate facial breakage. And also conditions are created for softening (growing) of the skin. Deashing is carried out in a longboat with constant stirring, for this, ammonium sulfate (fertilizer) is introduced into the solution.

The composition of the solution: FA = 3, ammonium sulfate - 2 - 3 g / l. The temperature of the solution is 35 - 38 degrees. Duration 2 - 3 hours. After deashing, the skin is washed in clean water. At the end, the skin is softened.

softening

The processing of the skin in the aquatic environment with enzyme preparations helps to remove the remains of proteins, the fat is stopped and reduced, the remains of keratin, carbohydrates and fats are removed, the breathability of the skin increases. The skins acquire softness, smoothness, silkiness, the finished skin becomes more elastic and viscous.

For cattle skins, animal pancreas, pancreatin or protosubtilin G-ZX are used as softeners. Softening is carried out for leathers that will be used for shoes, clothing and haberdashery.

The composition of the solution: LC = 3, the temperature of the solution is 38 degrees. When softened by the pancreas, it is crushed and an infusion is made for an hour in a ratio of 1 * 10 in a 2% solution of ammonium sulfate at a temperature of 38 degrees, or in the same ratio, a preparation of pancreatin or protosubtilin is dissolved in water - 1 g / l of one of these. Duration 4 hours. The completeness of softening is determined by the fingerprint. The skin is folded across the floor and squeezed with fingers, an imprint appears on the skin, which then slowly disappears. After softening, the pelt should be not swollen, soft with a silky face, and there should be no pink coloration when tested for phenolphthalein.

The liquid is drained and rinsed using a non-ionic surfactant - washing powder with continuous rotation. The composition of the solution: salt - 3%, powder 0.5% by weight of the hide. The water temperature is 32 degrees. Duration 30 minutes. Then washing in warm water of 28 degrees and ends in water at a temperature of 20 degrees for half an hour.

Pickling

When tanning leather with chromium tanning agent, it is necessary that there is an acidic environment in the thickness of the leather tissue. This contributes to the uniform distribution of tanning agent particles along the collagen fibers. You can pickle the skin with sulfuric, acetic or formic acid or a mixture of acids. The duration of pickling depends on the type of hide, thickness and density. Normally pickled raw materials have a milky white color. The composition of the pickling solution: FA = 2-5, salt 40 g/l, acetic acid 5 g/l, sulfuric acid - 1.2 g/l or pickling with one acetic acid 7 g/l and salt 50 g/l. Pickling time 24 hours. The temperature of the solution is 30 degrees. The rotation is continuous for 2 hours, then you can leave the longboat for the night.

At the end of pickling, the hide is checked. Check on a skin section with a methyl red indicator. The entire thickness of the cut should be red. The pH of the spent pickle liquid is 3 - 3.4.

Tanning

Leather tanning with chrome tanning agent is now widely used. Dry chromium sulphate with a basicity of 40 - 42% and a chromium oxide content of 25 - 28% is used for all types of leather, including cattle skins. Home craftsmen, when tanning hides, practice the one-bath method of tanning leather. After pickling, the hides are tanned in the same solution without unloading, a pre-dissolved dry tanning agent is introduced, and after the tanning agent has spread in the leather structure, the basicity of the solution is increased with soda. The tanning agent is fixed in the thickness of the hide, as a result of which the properties of tanned leather are acquired: strength increases, does not soak in water, and the welding temperature rises.

The pickle solution is heated to 40 degrees and the tanning agent is introduced in the amount of 9 g/l, the skins are rotated for 10 minutes every hour. After 12 hours of tanning, the solution is heated to 45 degrees and the dissolved dry tanning agent is again added in an amount of 9 g / l. The skins are mixed for 10 minutes every hour. Second tanning 24 hours. After 20 hours of tanning, baking soda 2–3 g/l, diluted in warm water, is added to the solution, the basicity of the solution increases. 4 hours before the end of tanning, neutralization is carried out in the same solution with the addition of baking soda 2.5 g/l and ammonium sulfite 2.5 g/l in 2-3 doses with an interval of 10 minutes. The temperature of the solution is 30 - 35 degrees. The semi-finished product after neutralization is controlled by the indicator bromcresol green. A section of the skin from a dense area should be stained blue. The pH of the waste liquid is 6 - 6.5.

The tanning of the skin is checked by a boiling test (for instrumentation). At the end of tanning, a piece of leather 5 cm by 5 cm is cut off in a thick place. The cut is examined for uniform penetration of the tanning agent into the depths of the skin. The color of the cut should be uniform. The control contour of the piece is measured, then the piece is dipped in boiling water for 3 minutes. If the skin is cooked and curled, then tanning is continued, if it has not curled and the shrinkage is less than 10%, then tanning is considered complete. Weldability of the skin is 80 degrees. Ready-made skins are pulled out, laid out on goats to drain the liquid, then to the bed.

bedding

After draining the liquid, the skins are laid out on the tables in a pile face to face for a bed for 24 hours, covered with cellophane. As a result of soaking, tanning agents are more evenly distributed in the structure of the skin in collagen fibers.

Part-time bakhtarma

The skins are laid on a deck and with the help of a two-handed scraper or a dead end they clean the bakhtarma into fills, thick places are trimmed with a sharp dead end. If possible, plan on a planer. The skins after tanning are pressed, passing through the rollers, and then planed on the machine. Thick skins are doubled.

doubling

Skin obtained from large raw materials (bull-calf, bull-calf, bull-calf) is subjected to doubling, sawn on splitting machines into 2 layers. The top layer is future genuine leather. The bottom layer is called split. The top layer is used for the production of leather furniture, important parts of shoes, bahtaryannaya for less important parts of shoes and haberdashery leather.

flushing

Skins are washed in running water, the initial temperature is 35-40 degrees and the final temperature is 60 degrees. Duration 30 minutes with continuous rotation. After washing, the skins are pressed, weighed and dyed.

Leather dyeing

To give the skin a certain color, it is processed by the dipping method in longboats in dye solutions with continuous rotation for 1.5 - 2 hours. Dye the skin with acid and direct dyes. When dyeing with acid dyes, an even color and deep penetration of the dye into the skin are obtained, but the color is not saturated. When dyeing leather with direct dyes, a beautifully dyed leather fabric of high light fastness is obtained. The disadvantage of direct dyes is the shallow coloring of the skin. When dyeing, these two types of painting are combined.

Dyes are used for dyeing leather: direct black “Z” for leather (consumption 2.7% of the mass of planed leather), direct brown “KX” for leather (consumption 0.4%), acid black C (consumption 2%) and acid brown K for leather (consumption 0.2%). Consumption of each dye according to the instructions. Dyes before dyeing are diluted in 40 times the amount of water at a temperature of 75 degrees, the solution is filtered.

Dyeing: LC \u003d 3, ammonia 25% diluted in 10 times the amount of water is introduced into a solution at a temperature of 50 - 60 degrees in a longboat (or concrete mixer) (consumption 0.5% by weight of planed skins). Skins are loaded. After 15 minutes, pour the solution of acid dyes in two prima with an interval of 15 minutes and dye for an hour with continuous rotation. An hour after the start of dyeing, acetic acid is poured (consumption - 60% of the weight of the dyes). Then, in 2 doses, a solution of direct dyes is applied and dyed for another hour until a uniform coloring of the leather tissue is achieved. Painting time 3 hours. After painting, the solution is partially drained to LC = 2, the fat composition is introduced and the skin is fattened by the dipping method for an hour with continuous rotation.

Fattening

Fatting leather is one of the important processes in the processing of cattle hides. The purpose of greasing is to give the leather tissue flexibility, softness and good appearance. Greasing is carried out in two ways: dipping and spreading, using a brush. The dipping method is more commonly used. The fat composition is prepared from special pastes. Currently, you can buy domestic drugs, as well as imported (Polish or German). Consumption according to instructions.

The fat emulsion can be prepared from the following components: alizarin oil 40%, fish oil 25% and sulfated fish oil 35% (total weight 100%).

At the end of fatliquoring, washing is carried out in running water at a temperature of 30-35 degrees for 30 minutes. The skin is then hung out to dry.

Drying

The skin is dried on a wire or poles in the air under awnings. In cold weather in warm rooms. After complete drying, the skin is laid out on the table with bakhtarma upwards and moistened with a sprayer with warm water, then the moistened sheets are stacked face to face and bakhtarma to bakhtarma, covered with cellophane and left for a day for a complete cure. After moisturizing, the skin is broken in special drums using rubber balls or ingots for 2-3 hours of continuous rotation. Wrinkled skins are taken out and dried.

Leather dressing

As a result of editing the skins, they increase in size, become thinner. The skins are again moistened with a foam rubber sponge or a sprayer from the side of the bakhtarma and placed in the feet for 2-3 hours. Then each skin is laid out on a wooden shield face up, pulled in all directions and they begin to fix the ends with nails or a stapler, trying to stretch without wrinkles. Dry the skins in vertical wooden shields, using both shield areas. Dry in a warm room for 12 - 24 hours. Then finishing operations are carried out.

The dried skins are inspected, the edges are cut off and polished on the machine from the bakhtarma side.

Application of the finish

In order for the face of the skin to have a beautiful appearance, you need to apply a special coating - the finish. Finishing gives the skin shine and color, as a result of which flaws are hidden and water resistance is increased. After degreasing the front layer with Kalosh gasoline or 5% ammonia solution, the first layer of finish is applied in the form of a primer. After 4 hours of drying, a second coat is applied in the form of a color coat and after 6 hours a third coat is applied. Then the skin is dried overnight. To give water-repellent properties, the face of the skin is covered with wax creams and polished with cloth. To obtain a smooth surface, the skin is ironed with a hot iron.

Production of leather from cattle skins on an industrial scale

Cattle skins must be removed in a layer with a longitudinal incision along the white line (the anatomical border of the fusion of the abdominal muscles in animals) from the head or without the head part of the skin, leaving the skin from the legs. The front legs should be skinned to the middle of the fetlock, and the hind legs to the middle of the hock.

The skin from the head of cattle must be removed in the form of two parts - the cheeks together with the lobash at one of them, and from the tail at a distance of no more than 8 cm from its base.

The isthmuses connecting the head part with the main part, depending on the weight group, must have the width indicated in 5.

The area, mass and thickness of cattle skins vary within wide limits. The mass of the skin is on average 7-8% of the mass of the animal.

The area of ​​the calciner-slicker is on average 40-60 dm2. The thickness in the area of ​​the croupon is 1.4-1.5 mm, in the collar 1.7-1.9 mm, in the floors 1.2-1.5 mm. Its skin is distinguished by a loose knit of bundles of collagen fibers and a relatively large thickness of the epidermis (3-4% of the thickness of the skin). The area of ​​the calf is 40-90 dm2, the average weight is about 3.5 kg. The calf is characterized by high uniformity in thickness (from 1.3 to 2.5 mm). The thickness of the epidermis of the calf is 2% of the entire area of ​​​​the skin, and the papillary layer is 30-35%. The absolute thickness of the papillary layer is approximately the same as that of the mucosa, but its relative thickness is different - it decreases to V3 of the thickness of the entire dermis. The bundles of collagen fibers of the papillary layer are somewhat thicker than those of the mucosa. The reticular layer of the dermis has a significantly greater (both absolute and relative) thickness and a denser and more complex 30 (looped) tie of collagen fiber bundles. Okoek has a thin and beautiful measure and is distinguished by uniform thickness and high strength, combined with softness and elasticity, which makes it a valuable raw material for the production of chrome leather for shoe uppers.

The outgrowth area is from 60 to 150 dm2. The thickness in the saddle area is 3-4 mm. Separate sections of the skin differ in thickness much more strongly than that of the calf. In terms of the ratio of the papillary and reticular layers of the dermis, the density and complexity of the interlacing of the fibers of the dermis, the outgrowth approaches the skins of adult animals. The outgrowth begins to show signs of sexual differences. On the neck part of the skin taken from the bull, roughness is usually clearly expressed - rough folds.

Compared to the calf, the outgrowth has a more strongly developed stratum corneum of the epidermis, it is characterized by regrown, coarse, dull, often slightly shaggy hairline, almost without fluff. The measure of leather made from outgrowth is much rougher and not as even as that of leather from calciner. The outgrowth, as a rule, is used to produce chrome leather for the uppers of shoes.

The area of ​​half-skin skins ranges from 120 to 250 dm2. The thickness in the paired state in the saddle area is usually 3-3.5 mm. The tapering of the skins of the half-skin is more pronounced than that of the skins of the outgrowth. The skins of the half-skinned, taken from the bulls, have a pronounced, furrowed. The histological structure of the skins of the semi-skinner is close to the structure of the skins of adult animals, however, the density of the tie of the mesh layer in it is somewhat less, the bundles of collagen fibers are slightly thinner, and the skin is smoother. Half-leather skins are used to produce chrome leather for the uppers of shoes and Russian leather, as well as for technical leathers.

The area of ​​bull skins is from 200 to 300 dm2. The thickness in the croupon area is 3.5-4.5 mm, on the collar - 2.5-3.5, on the floors - 2-3 mm. It is characterized by a strong roughness, extending to a significant part of the skin. The microstructure of the skins of bulls is close to the microstructure of the skins of adult animals. The skins of gobies are used to produce insole goods and yuft.

The area of ​​the barn is usually 200-400 dm2. The thickness of the barn, light in the rump, is 3-3.5 mm, in the collar - 2-2.5, in the floors - 1.5-2.5 mm. The heavy yalovka has a thickness of 3.5-4.5, respectively; 2.5-3.5 and 1.5-3.0 mm. Yalovka is characterized by great escapism. Often there is a polosity, especially in the skins of repeatedly calved cows, i.e., it is characterized by greater thinness, friability and an increased width of the floor than the floors of a normal skin. Light, medium and heavy yalovka is used mainly for the production of leathers for the uppers of shoes, and thinner skins are used for chrome-tanned leathers. The cowling is doubled, which makes it possible to obtain a split leather, suitable for use as leathers for the uppers of shoes (velor), lining and mittens leathers. Dense cowhide of heavy weights is also a raw material for the production of rawhide, saddlery and light sole leathers.

The area of ​​the bychyna ranges from 250 to 550 dm2. In bullocks of large size and mass, the thickness of the saddle is usually 4.5-5 mm, the collar is 3.5-4.5, the pop is 3-4 mm. The thickness of a light bullock on a saddlecloth is 2.5-3.5 mm, a collar - 2-3, floors - 2-2.5 mm. The regularity of changes in the thickness of the bull-calf over its area is almost the same as that of the bullock, but it is not typical for it to be full. Borushiness is absent or slightly expressed. The tie of bundles of collagen fibers of the dermis is somewhat denser than that of the yalovka, and the bundles themselves are slightly thicker. Light bullock is used mainly for the manufacture of elements of the bottom of the shoe. Heavy bovine gives valuable technical and saddle leather, as well as rawhide. Currently, bovine is used to make leather for shoe uppers.

The area of ​​the skins of the bull reaches 500 dm2, and the thickness in the black-backed part is 4.5-5.5 mm. The skin of the bull has the greatest thickness in the head part (up to 8-9 mm). The thickness of the floor and the edges of the saddlecloth almost do not differ. Borushistost is highly developed. The skins of the bull go, as a rule, to the production of plantar and technical leathers.