Comparison of Different Tanning Methods on Ostrich Leather and skin

Comparison of Different Tanning Methods on Ostrich Leather and skin

To determine suitable tanning method for tanning ostrich skin and producing properties of ostrich leather, bulk density, thickness, resistance and elasticity of ostrich leather in the main part of the 12-14-month-old ostriches (number = 15) were studied in different tanning methods (chromium, vegetal and aluminum).

Tanning ostrich skin, the mean bulk density and ostrich leather thickness of ostriches were 0/7 ± 0/0 g / cm2 and 1/7 ± 0/1 mm.

The rupture, resistance and elasticity force of chrome ostrich leather (0/33 ± 4/9 kgf), 2/197 ± 9/23 kg / cm2 and (3/53±0/7 percent ) were more than aluminum leathers (4/27 ± 5/5 kgf), kg 7/161 ± 7/26 kg / cm2 (4/46 ± 8/7%), and vegetal ostriches leather 0/13 ± 5/4 kgf, 7/.70 ± 8/21 Kg / cm2 and (1/40 ± 4/6 percent). (P <0/05).

In general, the mechanical quality of ostrich leather was better in chrome tanning than aluminum and vegetal leather.

An Introduction to Comparison of the Effects of Different Tanning Methods on Ostrich Leather and Ostrich Skin

Nowadays, ostrich leather is considered a luxury product, especially in the European, American and Japanese markets. Ostrich skin is tanned in different ways, such as vegetal, chrome, aldehyde, synthetic and aluminum.

In ostrich skin vegetal tanning, tannin and extracted vegetable materials such as bark and minerals are used, which usually make leather brown, but the resulting color changes due to combining with other chemicals and the origin color of the skin.

This method is most often used in the manufacturing of leather which are used in calligraphy and etching, or is used as mold to make stamps because they are not water resistant and their color will change.

Meanwhile, if they are washed with detergents and dried, their sizes are reduced and lose their softness and elasticity and will be hard and dry, so if you placed them in hot water, they will be very small and partially gelatinized.

This causes extreme dryness and rigidity of ostrich leather and, as a result, fragility. Since 1858, chrome sulfate and other chromium salts are used in chrome tannings, which are commonly used.

The resulted leather from this tanning method is smoother and more flexible than vegetal tanning and is less discolored and less shrinkage in water.

A half-made or incomplete ostrich leather is called Wet Blue which is due to adsorption of chrome color.

Comparison of Different Tanning Methods on Ostrich Leather and skin

In aldehydi, tanning, glutaraldehyde or oxazolidine compounds are used, but because of the dangers of formaldehyde for workers and causing allergy to some people they are not used currently.

In skin tanning of ostrich skin in synthetic, aromatic polymers such as novolac or noradol are used to produce white color.

In aluminum tanning, aluminum-mixed salts with different combinations of protein-containing material are used. This type of ostrich leather is used in manufacturing baby shoes or cars cabin leather because of the lack of chrome materials in it.

However, leather industry requires information on the characteristics of ostrich leather in terms of elasticity and other physical and chemical properties to find its exact application in producing of products.

Because the ostrich skin processing differs from the skin of other animals, the product and its usage vary somewhat, therefore, the purpose of this study is to investigate the effect of some common tanning methods (chrome, vegetal, and aluminum) on mechanical properties of ostrich leather

Comparison of Different Tanning Methods on Ostrich Leather and skinFig 1. Different parts of ostrich leather

Materials and methods

To evaluate the effect of different ostriches skin tanning methods, five ostrich skins of one to one and half years old were prepared, each of skin was cut in three parts from crosspiece and totally 15 pieces, and each five pieces was processed with chrome, vegetal and aluminum tanning methods.

The tanning operations included the preparation of pickle, wet blue, wet white, vegetal tanning and making colored crust from wet blue and white crust from wet white.

These steps were the same for pickle’s preparation, including soaking, liming, deliming, enzyming, degreasing and pickling. Wet blue was used for chrome tanning and wet white for aluminum tanning.

To prepare the colored crust from wet blue and wet white of the ostrich skin, the rechorome (in wet blue), neutralization, dyeing, fatlicuring, fixing, offload, drying in the air, softening and toggling carried out.

Vegetal tanning from pickle was carried out during soaking, washing, adjusting ion load, vegetal tanning with myrobalan, mimosa, basintan, tamol, lubricating, fixing and drying, and other operations were carried out to make leather like chrome and aluminum tanning.

The leather sample was taken from the main area of the ostriches skin or crown area (Fig. 1)

The mechanical properties of ostrich leather were determined by the national standard methods of Iran.

To determine the bulk density, three samples were taken from the original leather sample in the form of a circular cylindrical roller perpendicular to leather face with an approximate diameter of 70 mm. The mean of four points’ thickness of the sample was determined with a caliper.

By using Vernier caliper, the diameter of the samples was measured with a half-millimeter approximation and with millimeter ruler in two directions perpendicular to the ostrich grain and in two directions perpendicular to the thickness was measured again.

The mass of the test sample was weighted with a precision of one thousandth of gram and the bulk density was obtained from formula (1):

1) Da = 1.273 × 10 m / td2
In this equation, m is the mass (g), t is the thickness (mm) and d2 is the diameter (mm).

To measure the rupture force, resistance to rupture and elasticity, leather samples in dimensions of 10 to 50 mm was prepared.

The samples were fitted between pins of the puller (instron Model 4001) and after the rupture of the sample, the maximum recorded force was noted as the rupture force and the distance between the pins was noted as the sample length at the point of rupture (elasticity).

To determine the rupture resistance of 10 (Tn) was used from formula (2)

(2)Comparison of Different Tanning Methods on Ostrich Leather and skin

In this equation, F is the registered force (Kg), W is the sample width (mm) and t is the sample thickness (mm). The increase percentage of length at the rupture point (Eb) was obtained from formula (3).

(3)Comparison of Different Tanning Methods on Ostrich Leather and skin

In this equation, l1 is the distance between the pins at the rupture point and l0 is the initial distance between the pins.

Statistical calculations

One-way model (4) was used for analysis of figures in SAS software:

(4)Comparison of Different Tanning Methods on Ostrich Leather and skin

In this formula, yij is each of observations, u is average, i is the effect of three tanning methods and ij is the effect of the random error of each observation.

Comparison of Different Tanning Methods on Ostrich Leather and skin

Results and discussion

The morphological structure of the ostrich skin is similar to the skin of the poultry, but some of its features are similar to the skin of mammals.

For this reason, the characteristics of ostrich leather can be compared with light and heavy leather.

The thickness of the skin of the studied ostriches was 1.5 mm, with a range of 1.3 to 2.5 mm (Table 1). Similar figures for the thickness of ostrich leather were recorded.

In one study, the skin thickness of ostriches of 5 to 14 months was determined to be 66/0 ± 05/0 to 13/1 ± 05.0 mm, indicating getting more thickness of the skin with age gaining.

The thickness of the ostrich skin varies depending on the species, variety, age, sex, and areas of the ostriches body, so that the thickness of the leather of different species of livestock such as blue neck ostrich, black neck ostrich, goat, lamb and buffalo have been reported 1, 9/1, 9/0 , 7/0 and 1/1 mm respectively.

As you can see, the thickness of ostrich leather in the current survey is as high as the figures reported for ostrich leather and is more than leather thickness of often livestock species.

Table 1: The average and the standard error of physical characteristics of ostrich leather and skin.

Comparison of Different Tanning Methods on Ostrich Leather and skin

And: ** in each column is the significant difference in mean values at the level (P <0/05) and (P <0.01) : ns, the means difference was not significant (P <0/05)

In the present study, tanned vegetal leather had a higher but insignificant thickness of chrome and aluminum leather (Table 1).

The optimum thickness of leather clothes, handbags and boots is respectively 85/0, 25/1 and 45/1 mm, as well as lining and upper leather of women handbags are respectively, 5/0 and 8/0 mm respectively. Considering these cases, the most appropriate usage of ostrich leather is in the manufacturing of bags and boots, and is less suited to leather suits.

A wide range of forces (76/0 to 50 kg) was observed for tears in the studied leather (Table 1).

The amount of force needed to tear blue neck ostrich, black neck ostrich, goat, lamb and buffalo were registered at 32, 43, 26, 12 and 82 kg, respectively.

In the leather of domestic goats, the value of this attribute was 5/25 kg. (2)

As you see, the average of leather tear force amount of ostriches in this study is lower than mentioned figures in other studies on leather of ostrich, goat, and buffalo but higher than sheep leather,

In the present study, the average total skin resistance was 10/137 ± 68/19 (50 to 273 kg / cm2), which is less than mentioned figures in other studies, 163 to 214 kgf / cm2, 178 to 194 Kgf/cm2 and 10/137 ± 1/23 kgf / cm2 (see Table)

The range of goat and cattle leather resistance was reported as 94/203 to 93/254 and 93/254 to 92/305 kgf / cm2, respectively. Probably the difference is due to the difference in the thickness of the experimental ostrich leather with other sources.

The minimum resistance to rupture for full grain leather, furniture leather and outerwear of ostriches leather is 200, 170 and 200 kg / cm2, respectively.

Comparison of Different Tanning Methods on Ostrich Leather and skin

Cowhide, upper and lining leather of bag, should have at least 150, 180, 40 and 30 kg/cm2 resistance respectively.

The results obtained in this review are close to standard leather suits and more than upper and lining leather standards, and are therefore of good use in making ostriches leather clothes if they are well-processed and have a good thickness.

In this experiment, the highest mean values for tear, resistance and elastic force were obtained in tanned leather by chromium method (P <0.05), and then these values were reduced in aluminum leather and eventually vegetal tanned leather.

Particularly, there was a sharp decrease in in vegetal leather against chrome leather. Therefore, it can be said that the vegetal tanning method has an inverse effect on the physical properties of ostrich leather

A source of different tanning methods on ostrich skin was not obtained, so the influences of these effects were not obtained too, but according to the mechanical properties of furniture leather, for vegetable and chrome tanning respectively, 200 and 375 kgf/cm2, industrial leather products from 150 to 375 kgf/cm2 and chrome tanning leather for cloths and gloves 250 kgf/cm2, chrome tanned leather in this test can have better usage than aluminum and vegetal for the above goods, but due to the hardness of vegetal leathers, mostly they are used in hard and firm products such as luggage bags and book covers and aluminum leather can be used in car seat covers for tropical areas due to the lack of chromium oxide production.

The average elasticity of ostriches leather was 20/46 ± 05/4, which is as high as the mentioned figures for ostriches leather (50%) and goat leather (40%) and is less than
cowhide (80%).
The maximum tensibility of vegetal and chrome furniture leather products and is 50% and 75% respectively, and industrial leather goods are between 20% and 50%.

Considering the higher elasticity of chrome leather compared to vegetal and aluminum leather in this study, the use of chrome leather in furniture leather is better, although due to the unique properties derived from nodules of the ostrich skin, this type of leather is usually used for decorative and covering items (Table 1).

As it was said, vegetal leather is more suitable for making hard and industrial leather goods due to its less flexibility, and vegetal tanned ostrich skin can be used properly in manufacturing of bags, luggage, book covers and much more.

The resulting density is less than the apparent density of Shoe soles leather (1 and 1.5 g / cm 2) and to an acceptable level for other types of leather (Table 1).

In this study, there was a positive nonsignificant correlation between thickness with resistance such as leather of domestic goat’s leather, while in the evaluation of camel leather, a decrease in the amount of tear, resistance and elasticity was observed with increasing thickness of the sample (Table 2).

The most important issue which was considered in correlation between mechanical properties of ostrich leather, was positive correlation (3/0+) between firmness and elasticity (P <0.01)

Table 2: The correlation of physical features of ostrich leather

Comparison of Different Tanning Methods on Ostrich Leather and skin


Due to the high growth of breeding of this bird in the country, it is necessary to propose suitable strategies for the use of ostrich products especially for ostrich skin.

Meanwhile, how ostriches skin is processed for leather products is very important, and if methods used properly, it will play an important role in the production of optimal ostrich leather products and, ultimately, the economics of breeder and the leather industry.

The study found that ostrich leather has a good mechanical quality, such as other livestock, and, given the difference between different tanning methods, it is necessary to conduct wider practical studies to access higher quality, especially in vegetable leather.

From A to Z about skin and leather of ostrich

From A to Z about skin and leather of ostrich

Soft like feather, firm like skin of camel, from A to Z about ostrich skin and ostrich leather.
Ostrich leather which is produced of ostrich skin is one of the most precious products of this animal.

از سیر تا پیاز درباره پوست و چرم شترمرغ

The unique beauty, firmness, softness and durability are the features of ostrich leather. Ostrich skin looks very beautiful.
Compared with other types of leather, the natural fat in the ostrich skin makes the skin flexible and firm to dryness and cracking.
The distinguishing feature of this animal leather that makes it more beautiful is the presence of points related to the feather pedicel follicles on its surface.
Ostrich leather firmness is six times what is for cow leather.
This feature, with its remarkable softness, has led the product to be ranked among the world’s most expensive leather such as crocodiles.
On a large portion of the center of an ostrich skin and its cut edges, the effect of the hotbed of the feathers is clearly characterized as uniform holes.
Which makes the leather and the resulting product look very beautiful.
Usually, after slaughtering the bird and cutting the skin, cleaning, liming, and deliming are done then it prepares for tanning.
After entering the tanning stage like other types of skins, it is tanned and retanned by minerals and sometimes vegetable materials and after passing through different stages, the product eventually turns into precious leather.
The produced leather is usually dyed during production phase and in the drum or in the other usual manners.
After dyeing, the leather is completed and polished so that the beauty and natural pattern of the leather look is preserved and it has attractive, soft, brilliant and firm appearance.
Major usages of Ostrich Leather in the World
The distinctive features of this leather toward others are its different and beautiful appearance, softness, bending ability, and extreme firmness.
Most of the ostrich leather products include handbags, shoes, boots, coats and overcoat.
از سیر تا پیاز درباره پوست و چرم شترمرغ
European fashion halls have been using ostrich leather for making bags for many years.
But, in America, the leather of this animal mostly was used to produce boots and belts.
Due to the unique softness of ostrich leather, some automobile factories or car manufacturers have also used this product for the production such as covers for seat, dashboards, gearbox, steering wheel coat and even cavers in expensive cars in recent years.
The use of ostrich leather for car decoration is more common in Europe.
Well-known manufacturers of sporting goods in the world also use the remarkable strength, softness, and beauty of this leather to produce special sports shoes.
This type of leather has gradually entered in the production of home and office furniture in recent years.
Ostrich History
The ostrich history breed is full of ups and downs.
Ostrich breeding took place in 1850 in South Africa for the first time. It’s breeding and development was slow for fifty years, and it was mainly aimed for the meat.
Kelin Karoo In 1945 and after World War II, established a large company in South Africa to pursue the ostrich breeding industry and subsequently leather production.
Gradually local and regional demand for the animal’s meat increased, and the need for the slaughterhouse necessarily led to the creation of the first ostrich slaughterhouse in 1963-64.
The purchase and sale of ostrich skin began at the beginning of the 1970s, so a leather factory was set up by Kelin Karoo near the slaughterhouse, and he gained required knowledge and necessary training.
Before that, the information about ostrich leather was very low.
At that time, the skin was sent to UK leather manufacturers.
Ostrich leather was first used in cowboy boots in Europe and the United States.
But since 1980, the demand for ostrich leather in the United States and Europe has increased significantly.
Today, 150 years after the establishment of ostrich leather factories in the US and Europe, kelin karoo is still the best in the industry.
Capabilities in skin production on a farm
Each ostrich can live an average of 50 to 60 years.
But the appropriate age to mature and slaughter an ostrich in farms is about one year old.
The weight of the animal varies from 90 to 110 kilograms and its height ranges from 100 to 250 cm, depending on the male and female animals and their breed.
The female ostrich is capable of laying eggs at age 2 and produces an average of 50 to 70 eggs per year, on average, 40 eggs of each ostrich can be turned to chickens.
 The ostrich has about 35 to 45 kilograms of meat at the time of slaughter.
The amount of skin of each mature ostrich in the main countries in breeding this kind of animal, reaches an average of 12 to 16 square foot.
On average, per square costs $ 35.
Generally, on average 1.2 and 1.5 square meters (12 to 15 square feet) of leather of high quality can be produced from a mature ostrich in domestic farms.
This amount can be increased with respect to the correct principles of breeding.
According to comparative statistics provided by the Department of Animal Welfare of the Ministry of Agricultural Jihad, one female ostrich is capable of producing 40 chicks per year; each chicken will be mature and ready for slaughter in a period of 10 to 13 months.
While during this time, a female cow will only be able to produce one calf.
Accordingly, the production of skin caused by the supply of broiler ostriche in this period can be up to 100 square meters, while at the end of the breeding period of a broiler calf which is  longer than the required time for ostrich, Only a cowhide skin will be produced, which is maximum of 2.7 square meters.
Take a look at the prices of raw and tanning skin and leather of ostrich in the market
According to the information obtained in the market, ostrich raw skin is currently sold to leather-producing factories or intermediaries at the price of 60 to 90 thousand tomans with regard to the degree and quality of non-tanned leather, and the price of a tanned leather sheet of ostrich will be up to 500 thousand tomans.
By excursion to the leather market of Ferdowsi Avenue in Tehran and speaking with the suppliers of leather goods, you will find that there are currently no bags and shoes and coats made from ostrich leather in the domestic market.
And in very few cases, there are some artifacts in a few types are being sold in some special stores and well-known business centers that their prices are at an average of between 150 and 500 thousand tomans depending on the amount of used leather.
According to the managing director of the ostrich breeder co-operative, two factories have activity contract with the ostrich breeder cooperatives for the ostrich skin processing..
According to the information obtained by the author, some of  leather manufacturing units in the Charmshahr  of Varamin, over the past months, have started producing ostrich leather on a scale appropriate to the amount of skin provided by the ostrich farm, which Dalir Leather industries is one of them..
Dalir Leather Industries, by producing very beautiful leathers with high quality from ostrich skin, has planned to have negotiation with leading manufacturers of ostrich leather artifacts for export purposes.
Due to the high price and the lack of culture and mentality for ostrich leather products, these products are not offered in the country at the moment, and the domestic market does not welcome it.
Therefore, most of the final products such as bags, shoes, and clothing can be exported, and an ostrich producer said that so far part of these products have been exported to a limited extent to some countries such as the Netherlands and Belgium.
From A to Z about skin and leather of ostrich
Nutrition and quality of ostrich skin
Ostrich can reach slaughter weight at the age of 9 months
But most bird breeders, believes that acceptable leather cannot be produced from a 9 months old bird.
Considering the need to pay attention to ostrich leather production, the recommended age for slaughter is at least 12 months old.
While scientific studies conducted on ostrich farms in the origin ostrich breeding place, South Africa, suggest that ostrich skin fed on standard and recommended diets have a good quality even at 9 months of age.
The recommended formulation by Ostrich Nutrition Experts is based on fast-growing follicles, and growth of feather with more elastic and firm skin.
All of these together increase the quality of the skin.
Based on these studies, regardless of the age of puberty of bird’s skin, the management of new born chicken which influence growth rate in early weeks, chickens has been implicated that the breeding environment, the variation in the quality of alfalfa used in diets and the experience of chicken breeders are some of the factors affecting the formation and quality of the bird’s skin, and achieving high quality and mature skin even at the age of 9 months.
Such studies prove that special nutritional effects affect the growth of follicles and the quality of the skin. With special nutrition, you can have higher economic benefits in the skin field.
Quality and grading the skin
The general quality of the skin and the possible effects and defects caused by skin diseases
or its physical damage during the breeding period, the shape and state of the holes caused by feather follicles and possible genetic abnormalities in it, error in how to cut and open the skin,
and the size of the skin are considered as the important parameters in determining the quality and grading of the skin before tanning.
Defects caused in breeding period.
Hole or cutting caused by injury and wound, the skin surface scratch, the effects of old ulcer which has not recovered yet completely, sun burn, shelling, skin diseases such as blistering, blain or bacterial damage, germinated and incomplete feathers, being bitten, obvious wrinkle of the skin of the neck, the abnormality of the proportion of the part having feather and granules of the skin (crouponing)  to the normal part of skin, (should be on average, 60 to 40) are the possible defects on the skin during breeding period and before slaughter and peeling.
The existence and extent of each of these defects has significant effect on determining the degree of skin.
So that the simultaneous presence of three or four types of these defects, even to the low degree, can reduce skin quality up to 4 degrees.
The old or big sized ostrich has the skin with larger surface and big and ill-sorted which has no good quality.
Too young ostrich also has thin skin with tiny nodes closed to each other; it has no good quality too.
From A to Z about skin and leather of ostrich
Sizing skin
The area and size of the skin is another important factor in determining the degree of skin.
The area of the skin usually varies according to age, limb, obesity and emaciation and weight of the animal at the time of slaughter.
Usually the skin is categorized into 5 sizes, including + A, A, B, C, and D.
These dimensions range from the largest size, 156 dm (+ A ), to a minimum of 80 dm (this unit is measured in Iran based on square foot) for D size.
Proper cutting and opening the skin
One of the main points in having a high-degree, and high-quality skin is the style of cutting and peeling the ostrich and its final shape after opening.
Currently, in ostrich domestic slaughterhouses, ostriches are slaughtered on a chicken slaughter line and a livestock (sheep) slaughter line.
To cut the skin, the slaughterer should make a straight and accurate cutting line from the middle of the animal’s chest from the hew point to the tail, and another line of cut upright on the line to open the skin in the legs.
Another cut is also should be at the intersection of the animal wings.
Skin injuries and peak clipping of the animal
The damage to the ostrich skin caused by the cuts or scratches created during the breeding period reduces the quality of the skin, which greatly reduces the quality and value of the skin.
Reducing the damage caused by skin damage is one of the objectives of ostrich breeders.
Ostriches, especially the male animal, are often injured by their own or with each other’s pecking because of their aggressive and indocile character..
Usually an attacking ostrich, with its sharp peak, wounds the skin of another animal, especially the females.
Accordingly, professional breeders in order to keep the skin of animals of the farm healthy during the period from 9 to 13 months, they try to clip the peak of indocile animals of the farm, especially the males.
Recommendations for skin care after slaughter
1-Removing fat as soon as possible after slaughter.
Because fat does not allow salt to penetrate into the skin at a later stage, so the part containing fat will be fragile.
2- Skin immersed in a cold, concentrated salt solution until it is saturated with salt in a barrel about an hour.
3- Putting the skin on the ground so that its surface is below, then the lash part is covered with salt.
4- Five to six days after the blood serum is removed from the skin, after shaking the skin, the flesh is covered with fresh salt again, then it is put in a nylon bag and after packing, it is sent to Dalir Leather industries factory.
5. If you want to keep the skin in place for longer time, after second time salting, arrange them in a pilling and keep in the shadow.
Dalir leather industry has more than half a century experience and a pioneer in technology and leather upgrading in the leather industry of Iran.
It is a manufacturer of ostrich leather in various colors and tannings.