Leather raw materials of cattle. Weight of skins

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 classification of skins used for dressing leather for the production of leather products is carried out according to the animal species and age interval. Different skins have different properties and are used to produce different types of products.

Cattle skins

Depending on the type and size, the skins are used to make types of leather used in the production of gloves, haberdashery, shoes and outerwear.

Sklizok.

Skin of a stillborn or intrauterine calf. A distinctive feature is the crimson core. Sizes up to 700 cm2. It goes mainly to the production of likes.

Opoek.

Skin obtained from calves from birth until the end of milk feeding. A characteristic feature is faded and matted primary wool. Sizes up to 800 cm2. Serves as an ideal raw material for the production of husky and chrome leather.

Outgrowth.

Skins of calves that have begun to eat vegetable food. It is distinguished by dull hair that has undergone molting and a well-defined spinal strip. From this variety, the size of the skin begins to determine its weight. The mass of the outgrowth should not exceed 10 kg. Used for the production of husky and thin chrome leather.

Half-skin.

Skins of grown heifers and bulls, weighing from 10 to 13 kg. It differs from the outgrowth only in mass. In gobies, the skins on the neck have a characteristic thickening (borushiness), indicating a sexual characteristic. Used to make chrome leather.

Yalovka.

The skin of heifers that have reached puberty and cows. It is divided by weight into three groups: light (13-17kg), medium (17-25kg) and heavy (over 25kg).

Goby.

The skins of bulls, having a mass of 13 to 17 kg. They differ from the yalovka in a smaller area (by about 20%) and a pronounced roughness, reaching half the size of the skin.

Bychin.

Skins of castrated bulls weighing over 17 kg. They are divided into two weight categories: light (17-25kg) and heavy (over 25kg). They differ from the skins of uncastrated bulls in a smaller number of folds on the collar part.

Bull.

Skins of non-castrated bulls weighing over 17 kg. Differs in the big thickness and intensive browiness.

Half-skin, cowhide, goby, goby and bull are used for dressing such types of leather as nappa, morocco (rarely), velor, saddlecloth, napplak, shore, yuft, split leather.

horse skins

The skins of horses have a unique structure that greatly distinguishes them from the skins of other animal species. The front part of the skin (horse front) is rather thin and less dense than the back part (horse haz). This makes it necessary to divide the skin into two parts and use them for various leather products.

Sklizok.

The skin of a stillborn foal or embryo. Accepted by area, which ranges from 300 to 700 cm2.

Foal.

Foal skins weighing up to 5 kg. It differs from the slime in a larger area and an already pronounced mane.

notch.

Foal skins weighing from 5 to 10 kg.

Horsemeat.

Skin weighing more than 10 kg. There are light (10-17 kg) and heavy (over 17 kg) horse meat.

Horse skins are used for dressing several types of skins for various needs. From haberdashery production to tailoring of outerwear.

Sheep skins

Sheep skins are used as a raw material for hides only when their qualities are not suitable for the fur industry or fur coat production. Used for dressing such types of leather as husky, chevro, chevret, morocco (rarely), parchment.

Goat skins

Skins of only dairy breeds of goats are used for leather dressing. The remaining breeds supply down and raw materials for the production of fur products. Goat skins are dense, strong, with good uniformity in thickness. This makes them one of the best materials for leather dressing, used for the manufacture of shoes and leather outerwear. From this raw material such types of skins as husky, chevro, chevret, morocco (the best material) are produced.

Pig skins

Pigskins are the cheapest raw hides, but they have long been among the main types of hides and are used not only to produce a full range of standard skins, but also to imitate more expensive, improved types of leather made from other animal skins.

They are accepted by area, divided into three groups: small (300-700 cm2), medium (700-1200 cm2) and large (over 1200 cm2).

Upon acceptance, any type of leather raw material is classified by defects, divided into groups and goes to the appropriate types of processing.

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 a 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

Most types of leather raw materials are accepted by leather raw materials enterprises from suppliers and delivered to tanneries by weight. The mass of paired skins of various types is determined by GOST 1134-73 "Raw materials for leather". The mass of a fresh skin is understood as the mass of the skin removed from the animal after it has completely cooled down. This mass is the starting point in all technical and economic calculations of raw hide and leather production.

The mass of the skin depends on the type, breed, sex and age of the animal, as well as on the thickness, density and wool, the content of moisture and salt in the canned skin, and on the presence of various weighting agents. The conditions of feeding and keeping animals before slaughter are also of some importance.

As a rule, the skins taken from well-fed animals have a much larger mass than the skins of emaciated animals.

In some cases, differences in the mass of skins of animals of different breeds depend not only on their area, but also on thickness and density. For example, the mass of paired skins of meat cattle, which are thicker, is approximately 8% of the mass of the animal, and the mass of relatively thin skins of dairy cattle of productivity is only 6.5-7% of the mass of the animal.

The length and density of the coat have a great influence on the mass of the skin. The mass of skins taken from animals of the same breed, but at different times of the year, is not the same. The skin of animals of winter slaughter is characterized by thicker and longer hair, therefore, a greater mass. The content of fat deposits in the skins, which affect the weight of the skins, also depends on the time of slaughter.

Other things being equal, the skins of males, as a rule, have a greater mass than the skins of females. With increasing age, the area and thickness of the skins increase, which leads to an increase in their mass.

The mass of skins depends on the method and degree of conservation. Any method of canning is primarily associated with a decrease in the amount of moisture in the skin, so the mass of canned skins will always be less than the mass of a fresh skin. The standard for raw hides and skins establishes the ratio of the mass of the skins of cattle and horses of various canning methods, taken by weight.

The ratio of the mass of skins of various canning methods,%:

Paired skins 100

Frozen skins 95

Salted Raised Skins 87

Brine Skins 83

Dry-salted 50

Fresh dry 40

But these ratios may vary depending on the degree of preservation or shrinkage. During long-term storage of wet-salted canned leather raw materials, the moisture contained in the skins gradually evaporates, and therefore the weight of the skin decreases. Skins lying on the surface or at the edges of the stack are especially subject to shrinkage. The degree of moisture content in dry-salted and fresh-dry skins is influenced by the temperature and relative humidity of the environment.

Using the above ratios, you can always determine the mass of the skin of any preservation. For example, if a fresh skin of cattle has a mass of 20 kg, then after brine its mass will become:

x \u003d (20 83) / 100 \u003d 16.6 kg.

By the mass of the skin preserved by brine, it is possible to determine the mass of the skins of other methods of preservation.

So, if the mass of the skin preserved by brine is 16.6 kg, then the mass of the fresh-dry skin

x \u003d (16.6 40) / 83 \u003d 8 kg.

The presence of weighting agents in the skins and excessive moisture content in them lead to an increase in the gross weight of the skins.

Determination of the mass of skins is made taking into account discounts for weighting agents with an absolute error of up to 0.1 kg.

To determine the mass of skins during sorting at leather raw materials enterprises, very convenient dial postal scales VCP-50 and VCP-100 are used, which allow determining the mass of various visible skins with a minimum expenditure of time.

So, for example, according to A. D. Kurilyuk, 8.6% of the skins of adult deer and calves, 3.8% of fawns and non-blues, and 3.7% of skins are supplied to the procurement organizations of Yakutsk. In recent years, in connection with the delivery of deer to the state in a live form, the amount of raw leather and fur has been supplied to trade and procurement organizations much more.

The technological qualities of reindeer skins depend on the sex of the animals, their condition, and the time of slaughter. The skins of six-month-old females (1.9 kg) have the minimum weight; maximum weight - sires (8.4 kg). The weight of the skins of adult females is 1.7 kg lower than that of castrated bulls and 2.5 kg lower than that of male sires. The relative weight of deer skins ranges from 4.2% to 7.9% of live weight.

Different parts of the skins are not the same in their properties. The thickest and strongest are the rump, which have minimal stretch. The thin and weak areas are the floors.

The largest number of skins of reindeer calves have an area within 90 square meters. dm with fluctuations from 70 to 120 sq. dm. Their thickness on the floors is 0.4-0.5 mm, on the scruff of 0.2-1.5 mm. The skins of female calves are 0.1-0.3 mm thinner than those of male calves.

Their strength to break on average over the entire area is 4.53-4.78 kg per 1 mm2 in the longitudinal direction and 4.20-4.78 in the transverse direction. The collar and back have the greatest strength of calfskins in the longitudinal direction, and the rump in the transverse direction. The greatest extensibility, equal to 38-49%, these skins have in the transverse direction.

Skins of adult females have an area of ​​75-165 square meters. dm. As the age of the animal increases, the area of ​​the skin increases. In a 12-year-old female, it is 1.5 times greater than in a female at the age of 3.5 years. The average thickness of the skins in females is 1 mm, the strength both in the longitudinal and transverse directions ranges from 3 to 6 kg per 1 mm2, and the extensibility in the transverse direction reaches 76%, in the longitudinal direction - 62%; the collar has the greatest strength.

In males-producers and castrates, the skin area is 125-170 square meters. dm. The average thickness of the skins is 1.2-1.6 mm, with fluctuations from 0.7 mm to 2.3 mm. The greatest thickness is noted on the collar, the smallest on the floors. In terms of strength, the skins of males are somewhat inferior to the skins of females and are in the range of 3.5-5.0 kg per 1 mm2; the collar and back also have the greatest strength. The extensibility of skins ranges from 34 to 59%.

In the herd of animals of both sexes, it prevents deer from breaking away and leaving The fatness of animals has a great influence on the meat productivity of deer. Calves of both sexes have a lower width index behind the shoulder blades Spermatozoa in the appendages of reindeer appear 35-40 days before the rut