What is leather? Summary of all leather information 2019

What is leather? Summary of all leather information 2019

What is leather? How about Process

 

This is a question I received from many friends and customers when buying products at Thuy Bich. So I rewrite this article to provide basic knowledge for you, readers have a better view and understand more about leather in English is "Leather".

 

Leather is a durable and natural material made by animal skin. The most commonly used raw material is Cowhide. Used in small scale to modern mass production processes.

 

Leather is used to make many different items including: Shoes, car seats, clothes, bags, book covers, fashion accessories and furniture.

 

History shows that leather-based products date back to 2200 BC.

 

What is tanning?

 

Tanning is understood as the process of treating leather of animals to produce leather (crocodile leather, cow leather…), making the material more durable and more difficult to decompose. In the past, tanning was treated by the traditional tanning method using tannoit, a plant polyphenol chemical compound that has the ability to bind sustainably to proteins and compounds. Other high molecular weight organic.

 

The hides will be stretched onto frames and hung for several days in large tanks with increasing concentrations of tannin. During this process, the leather will become less absorbent and less susceptible to infections, mold attacks, the skin will be softer and be used in the manufacture of leather goods.

 

However, at the present time the use of manual tanning is no longer common. The introduction of mineral-based tanning technology (Chemical tanning) makes the job easier, increases the productivity, and the supply of leather for the market. After 1980, the use of pentachlorophenol and mercury-containing biocides and their derivatives was banned. The production of mineral tanning became more and more favored by the traditional manufacturing process. However, in some areas with a long tradition, people still use manual methods to retain the methods of handling ancient leather.

 

To learn more about the types of leather used in daily life, you can go to the article about basic types of leather.

 

In the above article, I have presented the common points, distinctions, similarities and differences, in order to bring the most intuitive information to the readers.

 

 


1. Where is the skin made from?

 

Until now leather products are still being produced manually. Because people still want to create products that have the quality of animal skin. From home furnishings to products for daily life or accessories such as: Men's Leather Belt (Belt Leather), Purse, Bags, Backpacks with very high durability.

 

=> So many objects have existed for decades from one cell to another in a family.

 

 

Leather is made into sheets

 

 

The skin is taken from any animal that humans once took meat. It sounds like something terrible, but the use of the skin is part of recycling to use this residue to create great products in life today.

 

Leather is a durable and flexible material formed through the tanning process of animal skins such as cow, buffalo, goat, lamb, deer, crocodile, ostrich ...

 

Leather is produced by a variety of methods, from individual to industrial.

 

The purpose of leather is to make a variety of leather products, including clothing, shoes, hats, wallets, belts, badges, book covers, parchment and upholstered furniture ... Next we will come to the concept of Tanning, which is the preparation for a clearer explanation of the types of leather below this article.

 

Leather products
2. Raw tanning process (Production processes)

 

Leather is produced from slaughtered animals such as: Cow, Buffalo, Goat, Sheep, Deer, Crocodile, Ostrich leather and this is done at tannery or leather companies with The original purpose was because they didn't want to throw away the skin so they looked for ways to take advantage of it to reuse it.

 

The leather production process is divided into three stages as follows:

 

Preparatory stages - Preparatory stages
Tanning - Tanning
Crusting
Surface coating (Surface coating (This is the stage to help the skin become more perfect)

 

a. First, the leather will be cut in half by placing in a long wooden frame marked with a certain code. After that, the whole pieces will be cut in half to facilitate further operations. In the first stages, the sheets will be cut in half and the symbols will be split into groups.

 

Each group will have about 100 plates to be put into the mixer to completely eliminate the fur on the surface layer, in addition to the treatment process is added water, Soda complex and Lime amount, this chemical group has The skin elimination effect is very effective and the finished product will be the skin completely clean the fur surface and prepare for the "Tanning" stage.

 

a. First, the leather will be cut in half by placing in a long wooden frame marked with a certain code. After that, the whole pieces will be cut in half to facilitate further operations. In the first stages, the sheets will be cut in half and the symbols will be split into groups.

 

Each group will have about 100 plates to be put into the mixer to completely eliminate the fur on the surface layer, in addition to the treatment process is added water, Soda complex and Lime amount, this chemical group has The skin elimination effect is very effective and the finished product will be the skin completely clean the fur surface and prepare for the "Tanning" stage.

 

=> We can summarize as follows: Marking - Soaking - Incubating - Liming - Staking - Cutting - Bleaching - Soaking

 

b. The Tanning stage will require quite a high level of skill in the workers to remove the meat, grease and a solution to help the chemicals to penetrate deeply and the skin. at the "Tanning" stage. At this point, many people will ask, "What is leather?", And then there is "What is tanning". I mentioned in the previous section. We do not confuse the strange process called "Tanning" and The durable material created in the "Tanning" process is "Tanning" 2.

 

After tanning, the skin does not have the perfect characteristics such as the surface is not flexible, rough, absorbed with water, the moisture is still high. This stage will be processed skin after tanning to create the leather material.

 

c. Carpentry is a process of drying and lubricating the skin that includes a lot of activities to soften and can include: splitting, shaving, dyeing, whitening and a number of other methods. The leather plates are put into the press to make the skin the required thickness, the rest of the leather will be recycled as rolled leather. Throughout this process, the worker must constantly check the details to ensure the thinness is eligible, the error in this process is very easy for a company to take great responsibility for inadequate delivery. quality as well as customer request quality products.

 

d. Next, the skin is put back into the 2nd mixer with a mixture of vegetable leaves, sap and water, dyes will also be added to make the skin resistant to water. Processing time at this stage is also faster and also much softer than the first time. Fine powder will be applied to the surface of the skin shortly thereafter, in order to create a layer of skin paste on the glass surface and of course this glass layer has been coated with a similar layer of powder. The skin will be put into the oven to dry.

 

Note: Always keep the temperature at a moderate level to avoid crooked, curly corners.

 

And after 4-6 hours, the skin will be easily removed and sprayed as desired and polished by machine. This process makes the skin brighter as well as more even in the surface layer. However, the machine must not be too strong or hard, which can easily tear the skin.

 

By now, we have realized that creating a pure leather is not easy at all, Every step requires meticulous, hardworking and whole-heartedly for the work of each worker. leather industry. The production process is so complicated, so here I continue to share with you the common types of leather, how to identify skin types, how to distinguish genuine and fake leather along with specific characteristics about it.

 

3. Tanning methods

 

The tanning process is largely different in the way chemicals are used, combining a number of specific methods. Here are some popular types:

 

a. Vegetable - Tanned Leather

 

Vegetable tanning is a manual tanning method that uses sources of tannin found in nature such as bark, fruit and leaves in liquid or powder form.

 

With a tough, brownish color, with the exact shade depending on the mix of materials and the color of the skin.

 

The brown color originates from the appearance of non-dyed leather.
With its unstable nature in water, it tends to discolor and to soak and let dry, it will shrink and become harder.
In hot water, it shrinks vigorously and partially clogs, becoming rigid and brittle. Boiled leather is an example of this, in which the leather has been hardened by soaking in hot water or boiling in boiling wax or the like (Typical products are Armor, Binding Covers, Hard-Sole Shoes)

 

This is also the characteristic of oak leather, exploited in traditional shoe polish.

 

This is the oldest and most popular tanning method in the world. To tan a leather, it takes quite a long time from 20 to 60 days.

 

For centuries, Tuscany tannery masters have found valuable “secrets” to continue this traditional craftsmanship passionately, while being flexible when combining traditional and traditional recipes. Advanced technology to produce a perfect leather.

 

b. process taning leather (Chrome - Tanned Leather)

 

Invented in 1958, processed using chromium sulfate or other chromium salts.

 

c. Leather with Aldehyd (Aldehyde - tanned leather)

 

By using the compound glutaraldehyde or oxazolidine, also known as "White Surf" due to the light cream color.

 

This type of leather does not contain heavy metal components like chromium, often used in shoes for infants and cars.

 

Fornaldehyd has been used for tanning in the past. However, at the present time, this substance is being phased out due to the chemical composition endangering production workers and the sensitivity of many people to Fornaldelhyd.

 

Chamois leather is a tanning form of Aldehyd that creates a porous and highly absorbent leather. Da Charnois is produced by using oxidized sea oil (traditional cod oil) to create aldehydes during production.

 

d. Alum Leather

 

Alum skin is transformed using aluminum salts mixed with a variety of binders and protein sources, such as flour and egg yolks.

 

This skin is not really tanned, rather this procedure is called "Tawing" and the collected material will turn back to rough skin if it is soaked in water long enough to remove alum salts.

 

e. Tanned leather (Brain Tanned Leathers)

 

Made by the process that requires a lot of workers in the labor process to create the finished products. Use emulsified oils, usually animals such as deer, cattle and buffalo.

 

Featuring soft, easy to wash.

 

f. Rose tanned leather
g. Synthetic - Tanned Leather
H. Rawhide
j. Formaldehyde Tanning

 

In another article I will clarify the remaining concepts. We only mention the widely used methods as well as the effectiveness in the tanning process.

 

4. Types of skin layers - Grades

 

This is the part where people will find it interesting and less boring. Because most of us have met a lot in life especially when we hold or see leather products.

 

And right now, try holding the nearest leather product by your side, take a closer look and find out if your skin type is one of the things I will list below.

 

If classified based on the layers of leather, real leather is classified into three types: Full-grain leather, Top-grain leather and Split / Bicast leather

 

a. Leather Grade 1 - Grain Leather (Full-Grain leather)

 

It is the top layer of the skin and retains its original state without any sanding, polishing ... This is the best quality skin, and only the cows are taken care of. in strict environment, clean hygiene can avoid scars from scabies, scrub some hemp rope, cacti or insect bites ... can use leather as full Grain leather.

 

Full Grain leather retains intact the skin particles, the top epidermis of the skin is so natural and durable. The skin surface still penetrates the pores, so Full Grain, if used in shoes, is very airy, especially in hot and humid weather. Full Grain used as a bag is very luxurious, when used will produce a natural patina layer that makes the product has a "color of time, soft ball and very smooth.

 

So that layer 1 skin is considered the highest quality skin layer. Products made from genuine leather will usually be: Furniture, Shoes made from whole leather.

 

Whole skin will be finished with an Anilin soluble medicine. Russian leather is a form of whole skin.

 

Depending on how the skin is treated and dyed, Full Grain divides into:

 

- Full Grain Aniline - Grade 1: Rustic leather, only dyed, not covered with 100% natural surface.

 

- Full Grain Semi-Aniline - Natural Grade 1 leather: A type of leather that penetrates and lightly coats the surface polymer to reduce dirt and water repellency, and still has a natural permeability.

 

- Full Grain Protected Leather (Pigmented Leather) - Grade 1 protective leather: the skin has a surface covered with a thicker polymer layer, no longer has natural permeability but the advantage is anti-fouling and waterproofing.

 

Do you own full Grain leather with some small scars, some insect bites or marks? Do not assume that it is not perfect, in fact for many people, you own very valuable leather goods.

 

b. Leather layer 2 (Top-grain Leather)

 

Top Grain Leather is the second quality leather after Full Grain, created when part of the top layer of leather is removed so it is quite durable.

 

Top Grain surface tea is repeated many times to make it smooth, smooth a surface coating and shape the skin grain, patterns ... according to the manufacturer's intentions.

 

Top Grain leather does not produce a natural patina during use, so with Top Grain leather products, manufacturers often create a very smooth, smooth, and soft artificial surface. like Full Grain skin on contact. Due to a top surface coating, Top Grain leather is more resistant to dirt, impervious as long as the surface coating remains intact. use.

 

This is also a good quality leather and is used very popular in fashion and household products.

 

c. Corrected Grain

 

Grade 1 leather surface is Grade 1 of cow leather, but the surface is treated rub, grinding to eliminate imperfections of skin pieces such as scars heal, scratches ...

 

d. Nubbuck Leather (Nubbuck Leather)

 

A lot of people confuse Nubuck with Velvet or Suede.

 

Nubuck leather, also known as Buck leather, is genuine leather, abraded to create a smooth cotton surface, when touched very smoothly thanks to the tight structure of the skin.

 

When you gently stroke the surface of the nubuck with your finger, these fine hairs fall to one side, creating a more translucent color than usual.

 

It is this characteristic that many people confuse nubuck leather with velvet fabric.

 

When using a damp cloth to wipe the surface of the skin, the color of the leather is darkened, because the nubuck skin has been rubbed against the outer protective layer so the leather's ability to absorb the leather is very strong.

 

e. Split Leather

 

Split leather is a type of leather made from the fiber of the rest of the skin after the leather used to make the top-grain skin has been separated.

 

During the split between the top-grain and split skin, the split skin can be split (thinner) into middle split and flesh split.

 

A very thick piece of leather like the middle split can split into many layers until it is too thin to split any more.

 

Split leather will then be artificially coated on the surface and embossed with leather grain (bycast leather). Split leather is also used to make suede.

 

The toughest suede panels are usually made from split split leather or from spilled skin (skin has been shaved to a standard thickness). Suede is usually rough on both sides.

 

Today, manufacturers will use different techniques to make suede leather from full-grain leather to increase product quality.

 

Depending on the purpose of use, people can also turn the suede up to make different products (visible face is not grainy).

 

However, this is not considered a standard form of suede.

 

f. Suede Leather

 

Suede, suede here is turned inside out, however suede for the product has separated a layer of outer surface, i.e. both sides are inside and processed to not look too rough .

 

It looks quite similar to Nubuck leather, but looking closely will not be as smooth as Nubuck, and the durability is also much inferior, because it is the inner skin, the loose fiber structure, not as durable as the outer skin.

 

Suede is inherently dirty and water-repellent, difficult to clean, but makes many types of products that are very nice, and easier to sew and style than Nubuck.

 

g. Bicast Leather (Bicast Leather)

 

Bicast leather (also spelled bi-cast or bycast leather) is a material made of a separate layer of leather covered with a layer of polyurethane (hence the material is also known as PU leather) or vinyl.

 

Bicast leather was originally manufactured for the apparel industry for glossy shoes, and later accepted by the furniture industry.

 

H. Patent Leather

 

What is Patent Leather

 

=> Patent Leather is not fake leather.

 

Patent leather is genuine leather that has been treated and covered with a material such as plastic

 

The finished leather is highly polished by adding an extra layer.

 

Dating back to the late 1700s, it became widely available after inventor Seth Boyden developed the first mass production process, using oil-based lacquer, in Newark, New Jersey.

 

In 1818. Modern versions were often a form of da bicast.

 

j. Bonded Leather

 

is a type of leather that uses dust and the skin of real leather mixed with glue, pressed together and covered with a polymer layer (usually quite thick) to create a surface like the upper layer skin. The use of rolled leather reduces waste during the process of using leather, good impact on the environment.

 

However, this type of leather has poor strength, making it difficult to create luxury for leather goods. Rolled leather is not classified as genuine leather, but its composition still includes genuine leather, so if a fire is used to try burning, the leather still produces a characteristic burning smell.

 

So I put them here so you can have more information to distinguish when choosing your favorite leather products.

 

Today, manufacturers are too good at creating surface coatings, so if sellers don't know skin well or are impersonal when advising customers, recognizing the quality of skin types will help. You know the true value of the leather item you choose.

 

5. From other animals (From other animals)

 

Today, most leather is made from animal skin, accounting for about 65% of the total production. Other animals used include sheep, about 13%, goats, about 11% and pigs, about 10%. Getting accurate data from around the world is difficult, especially for edible skin areas. The other animals mentioned below account for only one percent of the total skin production.

 

Horse leather is used to make exceptionally durable leather. Shell cordovan is a type of horse skin made not from the outer skin but the lower layer found only in horses called shells. It is appreciated for its mirror-like and anti-wrinkle finishing properties.

 

Lamb and goatskin used for soft leather in more expensive clothes. Deerskin is widely used in work gloves and indoor shoes.

 

Reptile skins, such as crocodiles, crocodiles and snakes, are noted for their distinctive patterns that reflect the size of their species. This has led to the hunting and breeding of these species in part for their skin.

 

Kangaroo skins are used to make items that are strong and flexible. It is the most commonly used material in bullwhips. Some motorcyclists prefer kangaroo leather to motorcycle leather because of its light weight and abrasion resistance. Kangaroo leather is also used for flat shoes, soccer shoes, and speed boxing bags.

 

Although ostriches were initially raised for fur in the 19th century, ostriches are now more common for both flesh and skin. Ostrich skin has a "goose" appearance that is characterized by the large follicles where hair grows. Different processes create different finishes for many applications, including upholstery, footwear, automotive products, accessories and clothing.

 

In Thailand, ray skin is used in purses and belts. Ray skin is very hard and durable. The skin is usually dyed black and covered with tiny round marks following the natural pattern of an animal's back. These bumps are then often dyed white to accentuate the decor. Rough ray skin is also used as a Chinese hilt, a sword in a Scottish basket and Japanese katana. Ray skin is also used for high abrasive areas in motorbike leather (especially in gloves, where its high abrasion resistance helps to resist wear in the event of an accident.)

 

For certain thicknesses, the fish skin is usually much stronger due to its diagonal fibers.

 

6. Environmentally favorable (Environmental impact)

 

The skin creates a number of environmental impacts, most notably due to:

 

- Carbon footprint of animal husbandry

 

- Use of chemicals in tanning processes (e.g. chromium, formic acid, mercury and solvents)

 

- Air pollution due to change process (hydrogen sulfide during degassing and ammonia during delimitation, solvent vapor)

 

a. Carbon footprint

 

An estimate of leather's carbon emissions of 0.51 kg of CO2 is equivalent to 1 pound of output at the retail price in 2010, or 0.71 kg of CO2 per £ 1 of output at the 2010 industry price.

 

b. Water footprint

 

A ton of waste or skin typically produces 20 to 80 m3 of wastewater, including chromium 100 100400400 / l levels, sulfur levels 200 20000800 mg / l, high fats and other solid waste and significant pathogen contamination. Italy. Manufacturers often add pesticides to protect the skin during transportation. With solid waste accounting for 70% of the wet weight of the original leather, the tanning process represents a considerable stress on water treatment installation.

 

c. Disposal

 

Skin biodegradation slowly slowly takes 25 to 40 years to decompose. However, vinyl and petrochemical materials take 500 years or more to decompose.

 

d. Chemical waste disposal

 

Jooti da Rajasthani, Jaipur, India

 

Tanning is particularly polluting in countries where lax environmental regulations, such as in India, are the world's third largest leather producer and exporter. To give an example of an effective pollution prevention system, the chromium load per ton produced is usually reduced from 8 kg to 1.5 kg. VOC emissions are often reduced from 30 kg / t to 2 kg / t in a properly managed facility. An assessment of the total pollutant reduction load that can be achieved by the United Nations Industrial Development Organization publishes accurate data on the reduction that can be achieved through advanced proven low waste methods. , while noting, "although the chromium pollution load can be reduced by 94% with the introduction of advanced technologies, the minimum residual load of 0.15 kg / tonne can still be difficult to use." landfills and sludge from wastewater treatment according to current regulations in some countries. "

 

In Kanpur, the "Leather City of the World" claimed itself with 10,000 tanners in 2011 and a three million city on the banks of the Ganges River, the level of pollution is very high, despite the industry crisis, the control committee. Pollution decided to close 49 highly polluting tanneries out of 404 in July 2009. In 2003, for example, the main wastewater treatment unit of the tanneries discharged 22 tons of solid waste. Store chrome every day outside.

 

In the Hazaribagh neighborhood of Dhaka capital of Bangladesh, chemicals from tanneries end up in the main river of Dhaka city. In addition to the environmental damage, the health of both local factory workers and consumers is ultimately negatively affected. After about 15 years of ignoring the supreme court rulings, the government closed more than 100 tanneries by the weekend of April 8, 2017 in the neighborhood.

 

The higher costs associated with treating wastewater than discharging untreated wastewater lead to illegal dumping to save costs. For example, in Croatia in 2001, the appropriate pollution reduction cost USD 70 USD / tonne of raw hides treated compared to USD 43 / tonne for irresponsible behavior. In November 2009, one of Uganda's key leather-producing companies was forced to pour waste water directly into a wetland near Lake Victoria.

 

7. Role of enzymes

 

Enzymes such as protease, lipase and amylase play an important role in soaking, degreasing, degreasing and bating activities of skin production. Protease is the most commonly used enzyme in skin production. Enzymes must not damage or dissolve collagen or keratin, but must hydrolyze casein, elastin, albumin, globulin-like proteins and non-structural proteins that are not needed for skin-making. This process is called bating.

 

Lipase is used in degreasing activities to hydrolyze fat particles embedded in the skin.

 

Amylase is used to soften the skin, to enlarge the grain and to give strength and flexibility to the skin. These enzymes are rarely used.

 

8. Preservation and conditioning Preservation and conditioning

 

The natural fibers of the skin break down over time. Acid skin is particularly prone to red rot, which causes powders on the surface and changes in consistency. Damage caused by red rot is aggravated by high temperatures and relative humidity. Although it is not chemically reversible, treatments can increase the processing power and prevent the decay of red rotten skin.

 

Prolonged exposure to relatively low humidity (less than 40%) can cause the skin to become hygroscopic, altering the fiber structure of the skin. Chemical damage may also occur due to exposure to environmental factors, including ultraviolet light, ozone, acids from sulfur and nitrogen pollutants in the air, or through a chemical action. after treatment with grease or oil compounds. Both oxidation and chemical damage occur faster at high temperatures.

 

Various treatments are available as conditioning. Saddle soap is used to clean, condition and soften the skin. Leather shoes are widely conditioned with shoe polish.

 

9. In modern culture

 

Due to its excellent abrasion and wind resistance, leather is used in rugged professions. The persistent image of a leather-wearing cowboy gave way to a pilot wearing a leather jacket and a leather helmet. When motorcycles were invented, some riders wore heavy leather jackets to protect them from road rashes and blowing winds; some even wear chaps or full leather pants to protect the lower body.

 

The flexibility of the skin allows it to be formed and shaped into balls and protective gear. Later, many sports used leather made equipment, such as baseball gloves and the ball used in American football.

 

Leather fetish is a common name used to describe a fetish appeal for leather wearers, or in certain cases, for garments.

 

Many rock bands (especially punk and heavy metal bands in the 1980s) are known for wearing leather clothes. Extreme metal bands (especially black metal bands) and Goth rock bands have loose black clothing. Leather has become less common in the punk community over the past three decades, because of opposition to the use of leather from animal rights advocates.

 

Many cars and trucks come with optional or standard leather seats or "leather sides".

 

10. Religious sensitivities

 

In countries with significant populations of individuals observing religions that impose restrictions on material selection, leather suppliers often clarify the types of leather in their products. For example, leather shoes have labels that identify the animal to which the skin comes. This helps a Muslim not to accidentally buy pigskin, and a Hindu to avoid cattle, this is to obey and respect religion. Many vegetarian Hindus do not use any type of skin. Such taboos increase the demand for religiously neutral skin like ostrich and deer.

 

Judaism forbids the comfort of wearing leather shoes on Yom Kippur, Tisha B’Av and at funerals. Also see Teffilin and Torah Scroll.

 

Jainism prohibits the use of leather, as it is obtained by killing animals.

 

11. Alternatives (Alternatives)

 

Many artificial leather replacements have been developed, often involving polyurethane or vinyl coatings applied to fabric liners. Many names and brands for such artificial leather exist, including "pleather", a "plastic leather" category and the Naugahyde brand.

 

Alternatively, the skin is cultured in a laboratory by means of cell culture. A number of companies have begun producing commercially grown leather.

 

Lastly, I would like to send my most sincere thanks to those who have patiently read all of my article, If I have a clumsy writing practice, I hope you will ignore it (I'm too bad !! T_T), There is some knowledge that is helped by technical brothers in the production workshop of help belts, so when you find out which is incorrect or you mentioned wrong, please comment via email box: thangvl81@gmail.com (Author: Ngoc Thang) or contact via the information here I will try to correct the article to become more complete.

 

Sincerely thank you !!!

 

Translator primary sources: https://thuybich.com/da-thuoc-la-gi

Questo sito web fa uso di cookies per funzionare correttamente e per raccogliere informazioni in base alle tue preferenze, anche da siti web di terze parti. Per poter continuare la navigazione utilizzandoli è necessario il tuo esplicito consenso per il loro utilizzo da parte di questo sito web. To find out more about the cookies we use and how to delete them, see our privacy policy.

  I accept cookies from this site.
EU Cookie Directive Module Information