How Leather Is Made

30 May, 2022 By Steel Horse Leather In The Journal

The process of making leather hasn't altered all that much over the last few thousand years. Making leather is a time-consuming and complex procedure that must be carried out with precision and attention in order to create high-quality leather with the same finish every time. The path begins with an animal hide and ends with a piece of leather ready to be changed into a leather bag, garment, or other leather product. Modern tanneries are clean and safe, with ample natural light. Automation has sped up the process, made it more efficient, and allowed for greater quality control.

Raw Material Leather

Skin material may be manufactured from practically any animal's skin, including pigs, sheep, goats, and crocodiles. The most frequent hide used, however, is that of a cow. The technique of manufacturing leather employs skins that would otherwise be discarded as a byproduct of the meat and dairy industries. Rather, the animal's skin is transformed into a beautiful and useful material that will last for decades by creating leather. Cows that have been branded, have had a lot of bug bites, have been housed near barbed wire fences, or have had electric cattle prods put on them, for example, might have hide damage.

Hides are delivered to the tannery and housed in a Beam House. They are preserved by being packed in rock salt, folded, and kept on pallets for up to 30 days. Desalting eliminates salt from the hides when they are ready for processing by tumbling and driving the hides ahead with a series of pegs. The salt is recovered and recycled in the Beam House for extra hide preservation. Haired hides are not desalted but instead soak for one to two days in soaking drums to rehydrate and remove dirt, salt, and certain soluble proteins. Hides are treated with lime at the same time to eliminate hair and soften and improve the hide. Following that, all skins are defleshed to remove any excess waste from the rear of the hides.

Tanning Leather

After the hide has been prepared, the second stage in the leather-making process is known as tanning, and it is responsible for converting the hides into leather by conserving the material and slowing decomposition. By conserving and preventing the deterioration of the hide, primary tanning turns pre-tanned hides into leather. Hides are placed in a tanning drum with chromium salts or vegetable tanning chemicals and cycled for up to eight hours. The salts and tanning compounds both preserve and soften the skin material. This ingenious piece of machinery constantly reheats the tanning solution, allowing for the finest possible penetration of the hides. Following that, fat liquoring adds natural bovine oils to the skin material, giving it strength and suppleness.

The skins are then shaved to a certain, consistent thickness specified by the quality of the finished leather product. After shaving, the skins are measured to assure precise thickness.

Tannage is classified into three categories. Vegetable tannage is the process of converting rawhide into leather using vegetable tanning chemicals. This procedure provides the skin material with more body and rigidity than the more common chromium tanning method. Mimosa, chestnut, and bark are the most regularly utilized vegetative components. Tannage with chromium is a synthetic tannage. Skin material that has been tanned with chromium salts has a delicate, mellow suppleness in the palm. Combination tannage combines chromium and vegetable tanning to produce a full-bodied, soft, and supple leather.

Tanning Method #1: Chrome Tanning

Tanners utilize a range of compounds to tan hides, as previously stated. 'Chromium' is the most often used tanning agent. It's a 24-hour procedure that yields a very stable, malleable, and long-lasting product. The bulk of leather produced globally is chrome-tanned since it is the fastest and most efficient method of tanning. Chrome-tanned leather is made by tanning it using chromium sulfate and other chromium salts. Because of the faint blue tint of the undyed leather, it is also known as "wet blue." The chrome tanning procedure is best suited for large-scale commercial applications because it takes around one day to finish.

This is the most popular approach in use today. It is more elastic and malleable than vegetable-tanned skin material and does not discolor or lose form as quickly in water as vegetable-tanned leather. However, because chromium is a heavy metal, there are environmental problems with this tanning procedure; while the trivalent chromium used for tanning is innocuous, other leftovers can include dangerous versions. The procedure was created in the second part of the nineteenth century as tanneries sought ways to speed up the process and make leather more waterproof.

The longer the hides soak, the deeper the penetration, which aids in concealing future blemishes and maintaining color consistency as the skin material in. When the hides are extracted, they are rolled, dried, and stretched.

Tanning Method #2: Vegetable Tanning

Vegetable tanning, which is considerably older, is slower than chrome tanning. Furthermore, as the name implies, the tanning chemicals are of vegetable origin, in the form of tannin from trees and plants. Vegetable-tanned leather can be pit- or drum-tanned. The hides are placed in 'pits' with pulped tree barks and stirred for a month or more during the pit tanning process. This allows the tannins to gradually penetrate the skins. The skins also shrink slowly, which strengthens the fibers. However, because pit tanning takes months, it raises the price of the leather.

Drum tanning is speedier. The hides are placed in drums with the tanning extracts, same as in chrome tanning. These are pre-reduced tannin treatments that deliver highly particular outcomes to the hides. The skins are then tumbled for a day or two, allowing the tannin to be absorbed into the hide. The procedure results in less shrinkage, but because of the tumbling, the hide's fibers endure more beating and the leather is often weaker and softer than pit-tanned leather.

The key differences between chrome and vegetable tanning

When compared to vegetable-tanned leather, chrome-tanned leather is softer and more supple. In addition, it does not discolor or lose form as quickly in water. It's also more dye-receptive.

When opposed to chrome-tanned leather, vegetable-tanned leather has more body and stiffness. As a result, the leather is more natural and matures organically like no other. However, colored vegetable-tanned leather frequently changes color when exposed to light. However, it is leather is rarely used for footwear.

Re-Tanning

A second tanning step may be required to thoroughly prepare the leather for its intended function. This will be repeated with either the vegetable mix or the chromium salts (or a combination), and the surplus moisture will be removed using pressure once again. The leather is then retanned to change its physical properties to fit its intended function. Leather is retanned using chromium salts, vegetable matter, or a mix of the two, resulting in a distinct hand or texture. After that, the hides are placed in a sammying machine for a second time to remove excess moisture. The skins are sorted and restored.

Following that, the hides are vacuum-dried, oven-dried, or air-dried. When vacuum drying, hides are put on a level, temperature-controlled surface, and a top is dropped over them to generate a vacuum. This vacuum allows the water to be swiftly removed, resulting in a tight, smooth grain texture. When leather is vacuum dried, it shrinks by around 5%. If the air-drying process is utilized, hides are strung on an overhead conveyor that moves throughout the tannery until they are totally dry.

Mechanical softening in the staking machine massages the skins, making them soft and supple. After staking, skins are thrown across horses, and as the hides dry, they form a "crust." The bleaching chemical used in re-tannage provides a suitable foundation for dyeing and allows for outstanding clarity and color consistency.

Dyeing Leather

Dyeing gives color to the leather. Tanneries are outfitted with a variety of dyes to color leather in a range of neutrals to vivid, saturated colors. The dyeing recipe is computer-generated to assure color accuracy and uniformity. Dying leather is a time-consuming procedure. Skins are placed in dye drums for eight hours before being cut to ensure that the dye has permeated the hides completely. The leftover liquid in the dye drums will be transparent, and the skins will be either air or vacuum dried. High-quality dyes allow for more saturation and color enrichment than regular upholstery leathers.

Dyeing is the process of adding color to leather, and it is done in the drums during the tanning process. As previously stated, chrome-tanned leather is blue in color. As a result, it's frequently colored a light tan to conceal the tanning process and provide an even finish that conceals scrapes and scars. Because dye absorption varies by location, minor color changes are to be expected. Loose patches of skin, for example, tend to absorb more color, making them look darker. These color and texture variations are part of the leather's inherent attractiveness.

You may have heard or read about 'aniline' and 'semi-aniline' dyes. They've become buzzwords, but it's not always apparent what they truly imply. The two dyes are translucent or semi-transparent, and they provide a little uneven finish that emphasizes the grain (here, meaning the structure) of the leather.

Aniline and semi-aniline dyes explained

Aniline dye is a transparent water-based dye with no pigments added. The unique marks and intrinsic qualities of the leather, like scars and wrinkles, are brought out as it absorbs. It also keeps the leather's breathability.

Semi-aniline dye has a trace of pigment or finish. This implies that the inherent qualities of the hide are retained, but the color uniformity is improved. When scratched, this type of leather does not leave a mark as easily as aniline-dyed leather. In addition to aniline and semi-aniline dyes, complete pigmentation is available. "It's like spray-painting a car," Uwe Maier says, describing how the color completely covers the leather.

Finishing

When the dyeing process is finished, the final stage in the leather-making process is finishing. This is the step at which the leather will be handled to ensure that it has the supple, flexible character that is so desirable in leather, as well as the shiny finish. A coating that not only protects the surface but also makes cleaning simpler. This procedure would be bypassed if bare leather was wanted.

The goal of finishing is to reduce the visibility of grain defects, offer the desired level of gloss, assure softness and malleability, and produce a more protected and cleanable surface. To soften the leather, skins are tumbled in temperature and humidity-controlled drums throughout the milling process. To stretch and tighten the fiber structure, hides are toggled onto stainless steel mesh frames for four to eight hours. Leathers made from higher-quality raw materials have less surface finish or pigment applied, allowing them to remain porous and breathable. Each hide is finished to a high standard. Naked leathers and hairy skins are not finished.

Faux Leather (Artificial Leather)

In the nineteenth century, some of the first leather replacements were developed. Nitrocellulose (guncotton) was invented in 1845 by German chemist Christian Friedrich Schönbein and was later transformed into collodion (pyroxylin) in 1846 by French scientist Louis-Nicolas Ménard. Collodion was first employed as a protective covering in wound dressings, and it was later used in textiles. Fabrikoid was a pyroxylin-infused cotton fabric invented in 1910 and patented by the DuPont Fabrikoid firm in 1915. It was weather-resistant and was widely used in goods such as upholstery, book bindings, linings, and automotive coverings. In the early 1920s, Naugahyde, a fabric covered with leather fibers and rubber, was originally utilized in women's purses before spreading to other sectors. Fabrics coated or injected with polyurethane and polyvinyl chloride have been the favored varieties of imitation leather since the 1960s, having the appearance and durability of real leather.

Artificial leather, often known as faux leather, imitation leather, and pleather, is said to have several benefits over real leather. It can mimic the look and durability of real leather at a lesser cost, and it is significantly less labor-intensive to produce. Furthermore, animal-rights organizations have denounced the leather-making sector for animal killing and cruelty. The desire for artificial leather alternatives for purses, shoes, apparel, and other fashion goods has been driven by a mix of practical and ethical factors. The faux leather business was predicted to be worth more than $50 billion in 2015.

Preservation and conditioning of Leather

With the passage of time, the natural fibers of leather deteriorate. Acidic leathers are especially susceptible to red rot, which results in surface powdering and a change in consistency. High temperatures and relative humidity enhance the damage caused by red rot. Despite being chemically irreversible, treatments can improve handling strength and prevent red rotting leather from disintegrating.

Long durations of low relative humidity (below 40%) can lead leather to become dehydrated, permanently altering the fiber structure of the leather. Chemical damage can also occur as a result of exposure to environmental variables such as UV radiation, ozone, acid from sulfurous and nitrous pollutants in the air, or a chemical reaction after any treatment with tallow or oil compounds. At greater temperatures, both oxidation and chemical damage accelerates.

There are a few techniques for properly maintaining and cleaning leather items, such as using a moist cloth rather than a wet cloth or soaking the leather in water. Conditioners and other treatments are offered. Saddle soap is a leather cleaner, conditioner, and softener. Shoe polish is commonly used to condition leather shoes.

Wrapping It Up

Finally, producing leather is a complicated process that necessitates the use of raw materials, water, and chemicals. As with bags, you should seek to get leather things that will last, both in terms of fashion and functionality. That is most likely another reason why Steel Horse Leader Company has become such a well-known name in the highest leather quality.

FAQ

What is Leather?

Leather is animal skin that has been kept to keep it from degrading. The manufacturing procedures determine the look and feel of the leather, as well as how it will grow with use, which is referred to as 'patina.' It's a natural substance that was one of man's first and most beneficial discoveries. We've used leather for thousands of years to protect ourselves from the weather, as tools and weapons, and as furniture and sitting.

What is the process of leather manufacturing?

The leather production process is divided into six stages, beginning with raw material preparation and concluding with final inspection and shipment.

What are the raw materials used for leather?

Raw material from Italy, Southern Germany, and Denmark benefit from a temperate environment in which confinement and management procedures do not cause noticeable harm to the cattle.

What are the drawbacks of using a hide?

Cow in other locations, on the other hand, maybe raised in harsh temperatures and subjected to barbed wire fences, branding, and electric cattle prods, which damage the skins.