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Файл:Innovative Technologies for Manufacturing Leather and Fur Products. A Study Guide
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hydroxide. Hypan is a water-soluble compound that contains nitrile-, amino-,
amide-, and carboxyl groups, and it is obtained by polymerizing nitrile with
acrylic acid in an aqueous medium, followed by the partial hydrolysis of
the obtained polyacrylonitrile with sodium hydroxide. It can suppress bacterial growth. Using hypan in primary processes with sheep skin allows reducing the process-based curing contraction as compared to curing with sodium
chloride by 8–10 % in average. Optimal hypan amount is 3–4 g per 1 dm2 of
the hide area when curing fur sheep skins. Using lower hypan amounts may
lead to undercuring of hides, which causes increasing bacterial content and
changing the structural components, followed by reducing the strength properties of green hides. Increased amounts of hypan do not considerably affect
reducing the process-based contraction. Therefore, using hypan in
the amounts of above 4 g per 1 dm2 is unreasonable. Increasing the amounts
of hypan per unit area leads to reducing the contents of unconnected greasy
substances in the fur skin and to some reduction in plasticity. Presence of
hypan in wastewater may help reduce pollution intensity, since hypan is able
to interact with organic and inorganic substances.
Nuclear irradiation. Comparatively new curing techniques include irradiation with gamma-rays from a source of Co60. This process is conducted
at the temperature of 18–20 °C in the open air. Gamma-rays kill microorganisms, chemical changes being inconsiderable within the hide. Raw hides
placed into a polyethylene bag and irradiated with a dose of 3 kJ/kg
(0.3 Mrad) can be stored without spoiling for 4 months. These raw materials
are processed in production without pre-hydration. It is found that irradiating
raw hides with gamma-rays leads to enhancing their physical and chemical
properties and is expressed as increasing the tensile strength of upper leathers
by 20–28 %, in increasing the fastness to wear of bottom leather by 20–25 %,
and in increasing the area yields of hides and fur skins. More intense action
of ionizing radiation may cause the collagen destruction. It is found that
the plasticity of green hides increases upon irradiating, with their tensile
properties being preserved.
Among non-conventional techniques aimed to enhance the characteristics of raw fur skins, ozonizing is of interest. Ozone actions are comprehen-
sive: Antibacterial, disinfecting, deodorant, and curing. Fur Industry Research Institute has shown that ozone neither affects the hide quality adversely nor tones down the furs, nor leads to any additional defects.
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2 . C L A S S I F Y I N G T H E B A S I C T Y P E S O F R A W
H I D E S A N D F U R S
2 . 1 . T y p e s o f R a w H i d e s a n d F u r s
According to the Russian standard GOST 1134-73, based on their
quality, all types of raw hides can be divided into four groups and four
grades.
Group 1. Slink and calf leather of any weights, foal skin weighing up
through 5 kg, sheep skin and goat skin of all sizes, and pig skins with the area
of 30–70 dm2.
Group 2. Kip skins, hides of young camels, horses, asses, and mules
weighing up to 10 kg, pig skins with the area of 70–120 dm2, and pig croupons with the area of 30–50 dm2.
Group 3. Hides of cattle, horses, camels, asses, mules, buffalos, yaks,
and elks weighing 10–17 kg, horse fronts and butts, camel half-hides of any
weights, pig skins with the area of 120–200 dm2, and pig croupons with
the area of over 50 dm2.
Group 4. Hides of cattle, horses, camels, asses, mules, buffalos, yaks,
and elks weighing over 17 kg and pig skins with the area of over 200 dm2.
Based on their quality, hides/skins can be divided by grades (I–IV).
The grade is determined by the number of defects and by their locations on
the hide. Three defects at the edge are equal to one in the middle of the hide.
Undamaged area of the hide is considered an effective area. Defects are assessed by a certain number of unities.
Hides that do not meet the requirements for Grade IV hides shall be
considered a cutting. It also includes hides already used in everyday life,
raggy, lumped sun-dried, toughened, and very smoky, as well as the halves
and parts of fells.
GOST 382-91 defines the purpose of using various raw hides to produce different leather types and the terms of giving them to tanneries.
Basic types of raw hides. Raw hides are divided into skins, hides, and
pigskins.
Raw skins are the those of cattle calves, such as slinks, calf skins, and
foal skins; hides of young camels, colts (slinks, foal skins, and pullet hides),
or sheep (Russian or range sheep skins). Based on its hair coat condition,
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sheep skins can be wooly, half-wooly, and beaver-lamb, while goat skins can
be steppe goat skins, milk-goat skins, and chamois.
Raw hides include cattle hides, such as kip, bull-calf, steerhide, bull hide,
cow hide, buffalo hide, yak hide, and elk skin; hides of horses, such as horsehide,
horse front, or horse butt; hides of adult and young camels; as well as ass hides,
mule hides, and hides of sea animals, such as walrus or seal hides.
Pigskins are those of pigs or hogs.
Whether a raw hide is suitable for producing full-value leathers is determined by their thickness, area substance regularity, weight, density, papillary-to-reticular dermis ratio, chemical composition, and defects, if any.
Hide thickness determines its being intended for producing one leather
type or another and green hide consumption per 100 m2 of leather. Substance
regularity per hide area determines the cutting-out properties of leather. Hide
area relates to those properties, too. Processing hides with areas of less than
20 dm2 is unprofitable.
Hide density determines the duration of processing them with chemical solutions and the strength of leather.
Papillary-to-reticular dermis ratio is important, since papillary dermis
determines the softness of leather, while reticular dermis ensures its tensile
strength. Nature of the corium fiber weave, such as inclination angle or packing density, determines the physical and mechanical properties of leather,
such as minimum tensile strength, wearability, etc.
Weight/area shall be taken for each hide separately. Weights of green
hides shall be taken upon their cooling and trimming/contouring.
Area of sheep or goat hides shall be found by multiplying the hide
length from the upper edge of its neck to the tail base by its width along
the line 3–4 cm below the fore shank pits. When finding the area of pig skins,
the skin length is measured from the upper neck edge to the line tangent
to the hind shank pits, while its width is measured by the line 8–10 cm below
the fore shank pits.
Hide thickness decreases from shell to double shoulder and from backbone to belly. This decrease in thickness is called tapering.
Thickness shall be taken at two points: One of them is on the right side
of the hide in the lower part of the butt; the second one defines its tapering
and is located on the same side of the hide, but in the upper part of the butt.
Specific types of raw hides.
Cattle hides can be raw skins (smaller animals) and raw hides (larger
animals). Raw skins include slink, calf skin, and kip.
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Slink means the skin of unborn or stillborn calves of any weights.
Its skin area is 40–50 dm2, and its shell thickness is 1.2–1.4 mm. Such skins
are distinct in quite a thick epidermis (3–4 % of the skin thickness) and loose
corium structure. Slinks are used to produce fancy leather.
Calf skin is the skin of suckling calves with their primary unshed coat, of
any weight. Calf skin area is 40–90 dm2, thickness 1.3–2.5 mm. Its distinctive
feature is a relatively thick papillary dermis (1/3 of the total hide thickness, while
it is 1/5 in an adult animal). Calf skin is used to produce the so-called “elk-upper”
(chrome-tanned leather used in making shoe uppers).
Kip is the skin of grazing calves with transitionally shedding coat and
a hot weight of up through 10 kg. Kip area is 60–150 dm2, its thickness
is 1.5–3 mm. Kips are used to produce elk-uppers.
Raw hides include heifer, bull-calf, ox hide, bull hide, and cow hide.
Heifer is the hide of one-year-old calves and bull calves weighing
10–13 kg. Its area is 120–125 dm2, and its thickness is 2.5–4 mm. Ranginess
is highly pronounced. It is used to produce elk-uppers, Russian leather, and
technical leathers.
Bull-calf is the hide of bull calves. Its weight is 13–17 kg, area is
200–270 dm2, and thickness is 3–4.5 mm. Strong ranginess is typical. Its tapering degree is higher than that of a heifer. Its neck is quite thick. The bullcalf is used to produce elk-uppers, inner soling, and Russian leather.
Ox hide is the hide of steer bulls weighing over 17 kg. It can be light
(17–25 kg) and heavy (above 25 kg). Hide area is 300–570 dm2, shell thickness is 3.5–5 mm. Ox hides are used to produce elk-uppers, Russian leather,
shoe-butts, inner soling, skirt leathers, technical leathers, and tawed leather.
Bull hide is the hide of intact bulls weighing over 17 kg. It can be light
(17–25 kg) and heavy (above 25 kg). Hide shell thickness is 4–4.5 mm, and
its area is 550–600 dm2. Bull hide is characterized by thicker skirts, i.e., neck,
head, and belly, and strong ranginess. Bull hides are used to produce shoebutts, tawed leather, technical leathers, and the light ones are also used
to produce inner soling.
Cow hide means the hides of cows, heifers, and stirks, the hot weight
of which exceeds 13 kg. It can be light (13–17 kg), medium (17–25 kg), or
heavy (above 25 kg). Its area varies within the range of 200–450 dm2. Light
cow-hide shell thickness is 2.5–4 mm, while it is 3–4.5 mm for the medium,
and 3.5–5 for the heavy ones. The hide is uneven in its thickness (tapering)
and has thin and weak belly parts (spready hide).
Horse hides. Key feature of horse hides is their well-marked difference in terms of the structure and properties of their front part (horse front)
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and lower end (horse butt). Boundary between them goes across the backbone at the 3/4 of its length from the head. Backbone represents an obdurate,
compacted, and hardly cuttable strip. According to their intended purpose,
horse hides can be horse front and horse butt. Horse front is of loose structure. It can be light (under 12 kg) and heavy (over 12 kg). Light horse front
area is 160–250 dm2, while that of the heavy one may be 170–300 dm2;
the light is 2.5–3 mm thick, and the heavy is 3–4 mm thick. Horse front is
used to produce elk-uppers. Horse butt (hinder part of the horse hide) has
two slopes located symmetrically at both sides of the backbone and called
shell. Shell is about a half of the horse butt area and has high density. Depending on their weight, horse butts can be light (under 5 kg) and heavy
(above 5 kg). Light butt area is 60–9 dm2, while heavy butt area is over
90 dm2. Shell thickness is over 3.5 mm. Horse butts are used to produce shoe
butts and inner soling.
Horse hides can be small or large. Small ones are slink, foal skin, and
pullet hide.
Slink is the skin of unborn or dead-born foals, unsuitable for fur producing. Skin area is 30–60 dm2, weight 1–2 kg. Slink is used to produce
fancy leathers.
Foal skin is the skin of foals that have already been at grass, unsuitable
for fur producing, and weighing up through 5 kg. Skin area is 40–90 dm2.
It is used to produce glove leathers and elk-uppers.
Pullet hide is the hide of young horses weighing 5–10 kg. Pullet
hide area is 120–200 dm2. Horse butt thickness is 2–2.5 mm, and horse
front 1.5–2 mm. It is used to produce elk-uppers.
Large hides include adult horse hides weighing over 10 kg. There are
light horse hides (10–17 kg) and heavy horse hides (over 17 kg). Hide area
reaches 400 dm2. Thickness of the front is 1.5–3 mm, butt is 2–4 mm.
Sheep skin. In leather industry, Russian and range sheep hides are processed. In terms of coat structure, sheep can be fine-wool, semifine-wool,
medium-wool, and coarse-wool.
Sheep skins have thin epidermis: 1.8–2.5 % of the skin thickness. Papillary layer is thicker than the reticular one. Papillary layer of rough wool
breeds is 70–60 % of the corium thickness, while that of fine-wool ones is
50 %.
Reticular layer consists of bundles of collagen fibers less dense than
those of other animals, and the bundles are weaved almost horizontally.
It also contains much fat that weakens the weave strength. Therefore, leathers fabricated of sheep skins have lower strength, stronger stretch, higher
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looseness, and better permeability. Areas of skins from Russian rough-wool
breeds are 60–80 dm2. Russian sheep skins are used to produce elk-uppers
(cabretta leather), clothes (Cape leather), helmets (helmet chevrette), filtration leather, and kid skin.
Areas of range sheep skins of fat-tailed, rough-wool, and adult karakul
breeds are 70–65 dm2. Leathers made of them are loose, extensible, and having slightly grain-break outer layer. Range sheep skins are used to produce
chevrette and wool sheep skin. Lower-quality sheep skins are used to produce lining leathers, as well as leathers for mittens and fancy goods.
Goat skins, regardless of their weights, are classified into milk-goat
skins, range goat skins, and chamois skins. Epidermis of goat skins is 2–3 %
of their thickness. Their papillary layer is less loose, while their reticular
layer is denser than that of sheep skin. Goat skins are cured by brining and
drying. Goat skins are classified as skins, not hides. Milk-goat skins belong
to dairy breeds. Their wool may be of different colors and is shorter than that
of range goat skins, and their corium is denser. Range goat skins are the skins
of wool- and fur-bearing goat breeds dispersed in plains. Range goat skins
are characterized by thick, dark, and solid-colored coat with undercoat and,
as compared to milk-goat skins, less dense corium. Range and milk-goat
skins are used to produce elk-upper, i.e., kid leather.
Pig skins. These include the skins of pigs, barrows, and boars. Depending on their green hide areas, they may be small (area of 30–70 dm2),
middle-sized (area of 70–120 dm2), and large (area over 120 dm2).
Hog skins (skins of non-castrated males) with the area of over 80 dm2
are distinct in considerably thicker corium in shoulders and front. Epidermis
of pig skins is quite thick (2–5 % of the corium thickness) due to poor hair
coat. At the borderline to epidermis, corium forms very uneven papillae;
therefore, the outer layer is coarse and rough, but has an increased rub fastness. Hog skin corium is not divided into the papillary and reticular layers,
since bristles, fat glands, and sweat glands occur throughout its thickness.
Deep penetrating bristles form through holes in leather. To eliminate this defect, special processing is necessary. Pig skins are used to produce chrometanned shoe-upper leather and for extra soft leathers, as well as flexible dressing and gloving leathers.
Fur raw material standards are set for one or several related raw materials. They include three core sections: Specifications; Acceptance Rules
and Test Methods; and Packaging, Labelling, and Transportation.
Basic components of the standard are:
1) Information on fur raw materials covered by this standard.
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2) Description of typical features of the raw material(s).
3) Requirements for the quality of hide/skin taking-up, i.e., flaying,
adjusting, and curing.
4) Stratification of hides/skins by strains, based on their sizes and on
the hair covering height, thickness, color, and softness.
5) Stratification of hides/skins by sizes, based on the sexual dimorphism, age variations, and individual characteristics of the animals.
Hide/skin sizes are mostly determined by their areas: By multiplying
the length (distance from interocular space to tailhead) by the middle width
of the hide/skin. For instance, caged silver fox skins are divided into two
sizes, depending on their lengths and widths. Skins of wild cats, beavers,
badgers, kolinskies, minks, nutrias, ondatras, lynxes, mountain weasels, marmots, yellow terrestrial squirrels, polecats, and bears are stratified by sizes.
6) Stratification of skins by color. 7 colors are defined for sable skins;
18 colors are for caged minks; 3 colors for silver fox; 2 colors for platina fox;
2 colors for black fox; 3 colors for blue fox; and 7 colors for nutria.
7) Stratification of skins by sorts. Skin sort means the totality of commercial properties of a certain species of animals procured within the same
area of a country and having roughly the same hair coat development. Most
winter furbearers are divided into three sorts.
8) Stratification of skins by defect groups. Skins having insignificantly
sized defects (tolerances) or without any are considered flawless. Tolerance
is an insignificant defect that does not entail any discounts of the skin procurement price. For instance, for fox skins, cut marks with the total length of
up through 10 cm and shot holes are considered tolerated, while for squirrel
skins, tolerance is three bird-shot holes.
Depending on defects and their sizes, skins are grouped by defects.
For instance, for fox skins, cut marks and stitches with the total length
10–25 cm are included into the second group of defects, and such skins are
discounted by 10 % of procurement price. Cut marks and stitches with the total length 26–50 cm are included into the third group of defects, and such
skins are discounted by 25 % of procurement price. Defects longer than
50 cm are included into the fourth group of defects, and such skins are discounted by 50 % of procurement price.
9) Information on discounts regarding the totality of defects. Totality
of defects means some defects that are simultaneously present on
the skin/hide. For instance, on the second-group skins, at most two firstgroup defects or one second-group defect are allowed. On the third-group
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skins no more than one third-group defect or two second-group defects are
allowed.
10) Information on skins defined as nonstandard. As nonstandard,
we usually consider skins having defects, the sizes of which exceed
the standard set for the skins with the last-group defects, as well as
moldy, burnt, or moth-/carpet eater-damaged skins. Nonstandard skins are
priced at 25 % of the first-sort skin prices.
Nonstandard are also skins procured in closed seasons, having thin
guard hair and almost no underfur, with winter hair that has just started developing.
11) Acceptance rules and methods of control. According to the standard requirements, skins shall be accepted by visual inspection of hair and
skin covers.
12) Requirements for marking, packaging, transporting, and storing
raw materials.
13) Supplier’s guarantee. The supplier shall guarantee the compliance
of skins with the requirements of relevant standards. Practically all standards
are accompanied with reference appendices containing a table for evaluating
skin quality as percentage to the trade-in value of the 1-sort skin, first group
of defects, large size, and relevant strain and color (per head price).
Effect of habitat conditions on the structure and properties of furbear-
ers’ skins and hairs. There are essential differences in skins and furs of ter-
restrial and underground animals or of amphibians and animals that live in
water the most of their life.
Animals living mostly in holes, such as mole or mole rats, the hair
cover thickness is practically the same in various body regions, and their
fur fibers are just slightly shorter than over and guiding hairs. In moles,
for instance, the difference between the hair lengths on the back and belly
is 1–1.5 mm. In color, back and belly hairs do not differ much, either.
In terrestrial animals, such as squirrel, sable, marten, fox, arctic fox,
and other furbearers that live on the earth surface, the difference in the downiness of various body regions is pronounced strongly. Back of such skins has
a more dense and thicker fur skin and covered with longer and thicker hairs
than their bellies. 5 to 20 thousand hairs are found on 1 cm2 of the back, while
the ratio between the fur hair and over hair thicknesses is 1:3 to 1:10. Hair
cover of terrestrial furbearers is darker for most species.
Otter, nutria, ondatra, mink, Eurasian beaver, and other semiaquatic
furbearers have hair coats on their bellies of the same thickness as on their
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backs, or even thicker. These animals have more hairs per 1 cm2 of the back
than terrestrial ones, and their amount ranges within 10–50 thousand hairs.
Fur-to-over hair thickness ratio is 1:11–1:19. Hair marrow in amphibian furbearers does not exceed 50 % of its diameter, while it is 50–94 % in
terrestrial animals. In amphibian furbearers, there is no essential difference
between fur skin thicknesses or hair colors on their back and bellies.
In marine cetaceans, such as dolphins, white whales, and whales, hair
cover has practically completely disappeared. In adult seals, hair cover consists
of coarse and sparse over hairs. Baby seals have thick and long hair coats.
Length of over hairs reaches 30–40 mm, and that of fur hairs is 10–16 mm.
There are 4–4.5 thousand hairs per 1 cm2. Baby seal bears this coat for
10–15 days.
Effect of climatic environment in the habitat on skin/fur quality. Differences in the properties of fur and skin may be observed in animals of
the same species, age, and gender, inhabiting different geographic areas.
Depending on their habitats, furbearers are classified into strains.
Strain means the totality of commercial properties typical of the skins of
a given animal species inhabiting a certain region or area. Strain is usually
named relevant to the name of the geographic region inhabited by the animal. Strain definition is based on skin sizes and hair coat heights, thicknesses, colors, and softness.
For red fox inhabiting forests, steppes, deserts, and mountains, there
are 38 strains, including Kamchatka, Primorye, Tomsk, Altai, etc. For squirrel living only in forested areas differing in their climatic conditions, there
are 10 strains: Yakut, Amur, Altai, etc. For otter living in water, there are
2 strains only: Northern-Siberian and Caucasian.
Skins of some animal species having no strongly pronounced geographic variation, such as wolverine or badger, are not divided into strains.
Seasonal variation. Changes in the fur and skin properties due to seasonal changes are typical of all animals. They have a complete change of
their hair coats, known as molting, which leads to changes in the hair coat
height, thickness, softness, shine, and color, as well as the thickness, density,
and color of skins.
In winter, animals have high, thick, and soft hair covering and thin,
but dense fur skin. By spring, winter hairs come off, while new, summer
hairs start growing. Fur skin gets thicker, becomes loose, and loses its fat
deposits.
In winter and autumn, their hair covering is shiny, while it is sad in
spring. In winter and summer, where hair covering stops growing, fur skin
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becomes pale. In fall and spring, with the development of pigment in
the bulbs of growing hairs, fur skin becomes darker.
In terrestrial animals, seasonal changes are more sudden than in aqueous ones. In non-hibernating animals, change of coat happens twice a year:
In spring and in fall. Hibernating animals, such as marmots, badgers, and
ground squirrels, start changing their coats in spring, upon interbout arousal.
It continues throughout summer and finishes in late summer or in fall, just
before hibernating.
In many animals, hair coats change their colors seasonally. For instance, ermines, weasels, white hares, squirrels, and white foxes usually have
brown hairs on their flanks and backs in summer, while they become snowwhite in winter.
Along with seasonal coat changes, there can be compensational
changes of animal coats. They depend on the formation and growth of hairs
in the body areas where the coat has been damaged due to mechanical effects, such as rubbing against burrow walls or fighting. New hairs are thicker
and coarser than the old ones, and they may be of another shade.
Seasonal changes in the properties of hair coats and fur skins represent
the core feature in grading the skins. In non-hibernating furbearers, skins are
of the highest quality upon the end of their fall change of coat to the time of
the spring one. Such pelts are accepted as grade one. Pelts of furbearers killed
in late fall or early winter, with underdeveloped guide hairs, over hairs, and
fur fibers, with their dense fur skins, and slightly blue hue at the back inner
side, shall be considered grade two. Pelts skinned in fall, with their non-fully
grown over hairs and underdeveloped fur fibers, having dark (blue) fur skin
at the inner side, shall be considered grade three.
In late winter to early spring, the hair coats of animals get duller and
start gradually get thinner (particularly in withers and flanks) or dried off,
while inner skin gets dryish. Based on the degree of the hairs growing dull
and thinning, pelts may belong to groups I, II, or III of defects.
Periods of hunting the main species of furbearers are controlled
strictly.
Dependence of pelt quality on the animal age and gender. Hair coats
and skins of animals change dramatically with advancing age. Young furbearers are normally born bare-skinned, with hardly visible lanugo. Shortly
after their birth, their first hair covering starts developing. It is very soft,
the over hair and fur fiber are scarcely different. Pelt quality of young furbearers is low, it is forbidden to hunt them.
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