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195
JALCA, VOL. 117, 2022
Abstract
Leathers made from exotic skins or rare parts of animals have
very good market value. e exotic leathers are usually preferred
because of their patterns, naturally occurring marks and their
unique structures. e objective of this study was to investigate the
feasibility of tanning the ovine stomach into novelty leather and
leather products. e ovine stomach was converted into an exotic
leather using oil tanning methodology, with goat oil as a tanning
agent. e rumen and reticulum parts of the stomach were taken
through pre-tanning, tanning and post-tanning operation. e
resulta nt leather had a di erent grain from t he ordina ry leather. en
mechanical operations like drying, toggling and staking were done.
Physical properties of the leathers were analyzed by determining
their thickness, tensile strength, elongation at break, tear strength,
ex endurance and ball burst extension test. e grain structure
of the leathers was analyzed using a light microscope. e results
of physical tests were poor compared to the grains of conventional
leathers since the composition of raw outer coverings of animals and
those of the stomach are dierent. e leather processed from this
non-conventional source has been found suitable for manufacturing
fancy small leather goods like coin purse, key holders, purses and
wallets.
Introduction
Exotic leather production refers to the tanning of the outer covering
of rare species of animals and other parts of animals that are not
used for making leather.1 e beauty, durability, texture, and
extraordinary properties of these leathers have fascinated many
people. Several types of skins such as crocodile, ostrich, emu,
al l igator,2 stingray, eel, snake, shark,3 pythons, frogs,4 lizards and
stingray sh5 have become popular as materials for making leather
for fashion apparel, footwear, accessories, and interior products.6
e use of exotic skins dates back to the early man. e hunting and
the gathering communities used skins from reptiles, birds, sh and
amphibians for adornment to their clothing or for their head-dresses
as well as for covering articles such as drums.7 e skins were made
less resistant to putrefaction by drying, they were made supple by
eshing and applying animal oils.7 Dierent animals have dierent
features that provide leather with varying properties and these have
Manufacture of Exotic Leather and Small Leather Goods
from Ovine Stomach
by
Pers N. Wanana,1 Benson Ongarora2 and Paul Tanu2
1Kenya Leather Development Council, Narob, Kenya
2Department of Chemistry, Dedan Kimathi University of Technology, Prvate Bag, Dedan Kmath - Nyer, Kenya
resulted in increased demand for various leather products in the
market.6
ere are four compartments of the stomach of a ruminant animal.
ese are the abomasum, omasum, rumen and reticulum. e
abomasum is the main diction and absorption compartment of the
stomach. Rumen, the bulk of the stomach, constantly mixes, turns
and digests the food.8 e inside of the rumen is lined with nger like
structures called papillae.1 e papillae help to increase digestion by
moving the food around inside the rumen. e omasum is made up
of many folds. e reticulum looks l ike a honeycomb.8 e reticulum
diers from the rumen regarding to the texture of its lining. e
reticulum is lined with ridges that form a hexagonal honeycomb
pattern. Despite the dierences in the texture of the lining of the
two parts of the reticulorumen, it represents one functional space.9
e process of converting raw material into exotic leather generally
involves three steps, with the rst step being pre-tanning. Pre-
tanning involves soaking, liming and unhairing, deliming, bating,
pickling and degreasing to remove unwanted components, hair,
adipose tissue, fats, etc., leaving a network of ber proteins.10 e
next step, tanning, involves reacting the pre-tanned material with
suitable ta nning agents such as chrome, veget able, combined tanning
or oil to produce a stabilized ber structure.11 Finally, post-tanning
which involves neutralization, retanning, dyeing, fatliquoring and
nishing in order to improve ber characteristics and to produce a
useful product.12 In the present study the rumen and the reticulum
parts of the stomach were processed into exotic leather with a grain,
which has a dierent variety from the ordinary leather.
Experimental procedures
Sample collection and preparation
e ovine stomachs were collected from a slaughter house in Nyeri
town, Kenya. e stomachs were cleaned by washing dirt with clean
water and cutting o the unwanted parts on the stomach. Goat oil
was obtained using the procedure described in literature.13
Pre-tanning
e ovine stomachs were wa shed using 400% water and 0. 5% wetting
agent. e stomachs were washed thoroughly and drained until
*Corresponding author email: periswayne@gmail.com
Manuscript received October 28, 2021, accepted for publication November 28, 2021.
196 Leather Goods from Ovine Stomach
JALCA, VOL. 117, 2022
they were clean. Liming was done with 200% water and 8% lime (in
two portions) for 24 hours, with the drum le to stand for every 15
minutes for every t wo hours. e tanning drum was drained and the
limed pelts were washed with clean water. During deliming process,
150% water at normal temperature, 2% ammonium sulphate and 1%
sodium metabisulfate were added and the drum le to run for one
hour. e cross-section was checked by phenolphthalein (colorless).
e delimed stomachs were then bated with 1% enzymatic bate for
one hour.
Tan n i ng
Tanning of the ovine stomach was carried out according to the
recipe provided in Table I.13 Goat oil tannage was conducted since
we had reported in our previous work that cod oil had poor rating in
terms of odor compared to goat oil. e resultant leather was then
dyed, horsed up, dried and staked.
Leather analysis
e leather was cond itioned using ISO 2419 test method. Physic al and
organoleptic properties of leather were tested.14 Physical properties,
which included thickness, tensile strength, elongation at break, tear
strength, ex endurance and ball burst extension test were measured
using IUP methods. Organoleptic properties, i.e., soness, color and
grain pattern, and general appearance were tested by leather experts.
Sink test and Eward eect were also conducted.
Structural analysis
e grain patterns of the exotic chamois leather from the reticulum
and rumen stomach were analyzed using a Light Microscope, Zeiss
Axio Zoom.V16. e samples were analyzed by cutting pieces
measuring10 mm by 10 mm, clamping them on the stage and the
micrographs for the grain pattern was obtained by operating the
microscope at (16×) magnication.
Results and Discussion
Sink test
When the stomach chamois leather was immersed in cold water, it
absorbed little amount of water. is could be because the amount
of water absorbed depend greatly on the porosity of the hide or skin,
thus indicating that oil tanned stomach is not very porous.15 e
leathers were bued on esh side with the aim of improving water
absorption capacity of the leather but no appreciable increase in the
amount of water absorption was noted. It was also observed that
bung and snung on either side of the stomach leather was not
eective.
Eward eect
Ovine stomach chamois leather showed unique Eward eect,
whereby when immersed in hot water at about 70°C, they shrunk
immediately and the area became thick and when the shrunken
leathers were immersed in cold water, they relaxed immediately and
regained 90% of its original area implying that the leathers passed
the Eward eect test. Oil-tanned leather is one of a few cases where
the leather exhibits reversibility eect following hydrothermal
shrinking.16
Table I
Recipe for oil tanning of the ovine stomach
Process Chemicals Amount (%) Time (h) Remarks
Pickling
Water
Salt
Formic acid
Sulfuric acid
150
10
0.8
1
2e pH was adjusted to 3.2
Pre-tanning Glutaraldehyde 0.5 2e pH was adjusted to 8.5 and the
skins were piled for 12 hours
Oil tanning Oil
(Goat oil) 30 6e skin was uniformly drummed
along with oil for 6 hours
Oxidation
(inside the drum) Hydrogen peroxide 6 4 e skin was drummed for 4 hours
Oxidation
(outside the drum) 12 e materials were hung on the
toggle drier at room temperature
Alkali wash
Water
Soda ash
Wetting agent
400
0.25
0.5
1e leather was washed three times
and drained.
Leather Goods from Ovine Stomach 197
JALCA, VOL. 117, 2022
goods to be deformed very quickly or even lose usability.19 Leathers
that have a lower tensile strength have a lower percentage elongation
and vice vers a. From Table II, it could be observed t hat the percentage
elongation of reticulum and rumen part of the stomach leather was
58.63 ± 1.24 and 45.01 ± 1.22 respectively. e elongation at break of
the rumen was poor since it was below the minimum recommended
value while the elongation at break of the reticulum part of exotic
chamois leather met the standard of 50% minimum.17 e observed
trend could as well be attributed to the honeycomb-like features on
the surface of the reticulum.
Tearing strength
e strength of the leather products in use is indicated by the quality
standard relating to tearing load. Table II shows that all the leathers
tested had more tha n 15 N/mm which is t he minimum recommended
value of tear strength of chamois leather and it was concluded that
the leather fullled the SNI-06-1752-1990 standard.17 e tearing
strength of the rumen part of the leather recorded lower tearing
strength as compared to the reticulum and this could be attributed
to dierent parts of the stomach serving dierent purposes and
therefore having dierent properties.18 Similarly, the characteristic
patterns on the surfaces of the dierent parts of the stomach could
be at play as pointed out earlier.
Flexing endurance
Flexing test was applied to the respective leathers and there was
no damage at 100,000 exes to any of the leathers. All the studied
leather samples passed the exing test hence, it could be inferred
that the method of tanning did not aect the exing endurance of
the leathers. erefore, the obtained exotic leathers could be used to
make small leather product that ex.
Ball burst test
e ball burst test is another physical property for testing quality of
leathers. It is intended to indicate the grain resistance to cracking.
Physical tests
e physical properties of the chamois leathers obtained thus are
summarized in Table II below.
ickness
e oil tannage, which is actually a “shrinkage” tannage, raised
the thickness of ovine stomach. From the results recorded in Table
II, it could be observed that the thickness of reticulum and rumen
part of the stomach leather was 1.22 ± 0.19 mm and 0.65 ± 0.12
mm respectively. ese thicknesses achieved by the exotic chamois
leather were within the minimum recommended values.17
Tensile strength
Tensile strength of leather is the greatest longitudinal stress leather
can bear without tearing apart. e tensile strength of leather is
determined by the brous structures that constitute the collagen
network structure and the modication of this structure by the
tanning agents.16 e minimum tensile strength for chamois leather
should be at least 7.5 N/mm2.17 is study found the tensile strength
of the exotic chamois leather was higher than 7.5 N/mm2. e
reticulum part of the exotic leather had a tensile strength of 15.64 ±
0.86 N/mm2 while the rumen part had a tensile strength of 11.51 ±
0. 61 N/mm 2. Leather obtaine d from the rumen recorded lower tensile
strength as compared to the tensile strength of the reticulum part
and this could be attributed to the fact that leather is anisotropic in
nature.18 e hexagonal honeycomb-like structures on the reticulum
may also be playing a role as a reinforcement of the belt, thus ma king
it less susceptible break compared to the rumen.
Elongation at break
Elongation refers to the abi lity of a leather product to lengt hen/stretch
when stress is appl ied to it and represents the ma ximum extent leat her
can stretch without breaking. Elongation is an important property
to be considered when choosing leathers because a low elongation
value results in easy tear while a high elongation value causes leather
Table II
Physical properties of ovine stomach leather
Physical properties
Exotic chamois leather
Reticulum
stomach leather
Rumen stomach
leather
Standard value
SNI06-1752-1990
(minimum)
ickness (mm) 1.22 ± 0.19 0.65 ± 0.12 0.3 - 1.5
Tensile strength (N/mm2)15.64 ± 0.86 11.51 ± 0.61 >7.5
Elongation at break (%) 58.63 ± 1.24 45.01 ± 1.22 >50
Tearing strength (N/mm) 33.01 ± 0.51 28.90 ± 0.61 >15
Flex endurance at 100,000 exes No damage No damage No damage
Ball burst extension (mm) Grain crack 7.79 ± 0.21 5.88 ± 0.22 6.5
Grain burst 8.45 ± 0.22 6.93 ± 0.06 7
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From Table II, it could be observed that the reticulum part of
chamois leather samples tested had values 7.79 ± 0.21 mm, 8.45 ±
0.22 mm for grain burst and grain crack respectively, which are
higher than the minimum recommended values of 6.5 mm and 7.0
mm. e rumen part failed the test since it recorded lower values of
5.88 ± 0.22 mm and 6.93 ± 0.06 mm respectively for grain crack and
gain burst against the above minimum recommended values.17 Pre-
tanning, ta nning and post tan ning processes and a lso the type of raw
material are known to aect the grain crack and grain burst test.20
Howbeit, in this case, it is evident from Table II that the thickness
also aected all the analyzed physical properties. e rumen that
recorded lower thickness value consistently displayed lower values
in all the conducted tests.
Color and dyeing
e stomach leathers were yellow except for papillae which were
light brown. According to the SNI 06-1752-1990, preferred color
of chamois leather is yellow to nearly white.17 e color possibly
indicates that oxidation on the papillae was faster and more severe
than on the stomach, and a brown color in oil tanning always point
to a fast rate of auto oxidation.15 Due to poor color uniformity of the
exotic chamois leat her, the leathers were dyed and this gave uniform
color to the leathers as shown in Figure 1 below. e color intensity
of the applied dye ranged between 6-7 as shown in Table III.
Organoleptic properties
e table below shows the organoleptic properties of the exotic
leathers from ovine stomach.
e evaluated organoleptic properties of the chamois leather
included soness, color intensity, general appearance and grain
pattern. So leather tends to increase its water absorption and
exibility, so it will provide comfort during use15. From Table III,
it can be seen that organoleptic properties of the leathers obtained
from this study were above average on a scale of 10. Color intensity
of the stomach leathers ranged between 6-7. is shows that the dye
had penetrated. e obtained leather had unique appearance which
was dierent from the ordinary leather. Reticulum leather was lined
with ridges that form hexagonal honeycomb-like patterns while
rumen leather was covered in small nger-like projections called
papillae, which are attened. ese features gave the leathers an
appealing look (given the general appearance rating of 8) as shown
in Table III.
Grain structure
e grain structures of the leathers obtained from reticulum and
rumen parts of the stomach are shown in Figure 2. e reticulum
leather is lined with ridges that form hexagonal honeycomb-like
patterns while rumen chamois leather is covered in small nger
like projection which are attened. e retention of the primary
features of the raw materials is what gives chamois leathers their
aesthetic look,3 hence their high pricing due to high demand.
Most customers are willing to pay more just to access chamois-
based products since the uniqueness in the products gives them the
inherent social status and ornamental value. erefore, products
manufactured from ovine stomach chamois will nd a market
share due to this factor.
Table III
Organoleptic properties of stomach leather
Organoleptic properties Reticulum leather Rumen Leather
Soness 6 7
Color intensity 7 6
General appearance 8 8
Grain pattern 9 8
Figure 1. Photographic plate of nished ovine stomach chamois leather
Leather Goods from Ovine Stomach 199
JALCA, VOL. 117, 2022
Acknowledgement
We would like to acknowledge the African Development Bank and
Dedan Kimathi University of Technology for funding and Kenya
Leather Development Council for the technical support that made
this work a success.
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e leather obtained from the ovine stomach was used for making
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can be used as a source of raw material for exotic chamois leather
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Conclusion
e ovine stomach, a non-conventional source of leather, was
used to produce a new variety of exotic chamois grain leather. e
oil tannage impacted on the soness and stretch of the obtained
leathers. e thickness of the stomach increased to a reasonable
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Figure 2. Optical microphotographs (16X) of stomach leather: Reticulum (A), Rumen (B)
Figure 3. Products made from exotic ovine stomach leather: wallets and key holders
A B
200 Leather Goods from Ovine Stomach
JALCA, VOL. 117, 2022
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