Leather Information

Raw skins go through many processes during tanning. The type of hide and the desired end product determines what specific procedures are employed for the desired end result.

Hides are cured first through salting and/or drying the hide after it has been harvested. As hides are normally a by-product of the meat processing industry this step often takes place inside a meat-packing facility. It’s important to do this fairly quickly in order to arrest the natural decaying process.
Hides can be cured in one of two ways: • Brine-curing is the preferred method as it’s quicker and easier. The hides are put in large tubs or vats and infused with salts and disinfectant. After about 12 hours, the skins are completely cured, ready for the next stage.
• A more primitive method is Wet-Salting. It’s accomplished by salting the hide, then placing many skins on top of each other making a damp clump of skins. Left to cure for a month, the salt is completely absorbed into the skin, preserving the hide.

Once cured, the hides are soaked and rinsed with water. This rids the skins of salt residue, dirt, and other unwanted materials.

After soaking, the cured hides are processed on a machine that removes all remaining flesh. The hides are then immersed in a mixture of lime and water, loosening the hair from the skin. After about a week, the hair is taken off the hide by machine.

Scudding is done by humans.  Stray hairs, etc., missed by the machine are removed from the hide by hand tools.

Hides are then de-limed with acid. After the lime is removed, hides are exposed to enzymes.  This process evens the grain of the leather. The resulting product is soft and flexible leather.

Vegetable tanning agents create some flexibility in the leather, but its primary characteristic is to develop tough, durable leathers. Example application would be luggage, leashes, belts, straps, saddles, and harnesses. Vegetable tanning is accomplished in large vats where the hides are covered with tannin. Tannin comes from the bark, wood, leaves and fruits of chestnut, oak and hemlock trees. From beginning to end, the hides are exposed to increasingly stronger tannin solutions. As with all tanning, vegetable tanning stops the decaying process.

Mineral or chrome tanning produces softer leathers with more stretch, such as those found in purses, briefcases, shoes, gloves, garments, etc. Initially, the hides are pickled with acid and salt, then, soaked in a chromium-sulfate solution. This process is much faster than vegetable tanning, typically a 1-day project.

This is a newer technology on the market.  Micro acrylic resins are impregnated into the leather and can be controlled to create a soft chrome-tanned like leather to firm veg-tanned like leather  This process is sometimes call “Syn-Tan”  leather.  It will emboss with pressure only (veg-tanned requires heat and pressure.)  However, it is difficult to work with as the leather can be affected by simply pulling on it.  You will find this leather in applications where embossed yet soft is the criteria.  For example, a handbag that has an embossed image but is otherwise soft supple leather is undoubtedly syn-tan.

Hides are often reprocessed through the tanning cycle to improve and attain a specific physical characteristic.  In many cases a combination is used to develop leathers that have the positive characteristics of each tanning process.  This is often the case with upholstery grade leather.

A hide that has been fully tanned, but not colored in any way is called a crust.  It is a light grey color belying the notion that many people have about the “natural” color of leather.

The hides then are dyed. Typically the dyes used are aniline dyes.  This is accomplished in vats of heated dye solution where the dye permeates the entire cellular structure of the hide. This process may also add moisture back into the skin. Vegetable tanned hides may be soaked with oil, grease and waxes to make them more pliable.   This is a process often referred to as “stuffing.”

The final step is finishing the skin. Depending upon its intended application, this step may include covering the grain surface with a chemical compound, then brushing, buffing and sanding the surface. Leathers which are sanded for long periods of time become brushed or Nubuck leather. The sanding step may also reduce the amount of imperfections in the hide. However, it erodes the epidermis, which is the most important part of the hide, contributing the dominant component of strength. Waxes, glazes, oils, and other solutions may also be added.

Most upholstery grade leather goes through a final phase. One, or in many cases several flexible, pigment coatings are applied to the leather which determines the color presented on the outside of the hide, then a clear-coat is applied, which determines the sheen. These color coatings are normally acrylics with a urethane clear coating over the top that enhance the wear, fading and stain resistance of the leather.  Both the color coat and clear coat act as a cohesive film that adheres to the leather surface.

A second technique is nitrocellulose based chemistry. This coating technique does not form a film but rather sits on the leather as individual particles. This has less stiffening effect on the leather, but lacks the durability of urethane. These finishes have a softness that mimics pure aniline-dyed unfinished leather. While it offers a soft feel, a nitro finish scratches fairly easily.

Definition: Typically chrome tanned leather representing the epidermis of the hide. It is aniline dyed (infused dye in to the fibre structure of the leather) then a topical pigment coating (commonly misunderstood as "leather dye") and clear coating are applied to the surface. These coatings represent the color and sheen on the leather. The color coat is either an acrylic or urethane or occasionally a blended resin. The clear coat is usually a urethane for toughness and durability.  The resins have both adhesion (to the leather) and cohesion (to itself) properties. These resins then create a continuous film on the leather’s surface. (See Addendum B.)

Attributes: If it’s a top-grain leather, then this is the most durable type of leather as it has the strength of a top-grain and the protection of a urethane coating on the leather. 

Advantages: Highly durable, will withstand the rigors of an active household or commercial environment. It is fade and stain resistant. Easy to maintain, this leather will last many years if properly conditioned. This is the correct leather for an active household environment.

Disadvantages: If heavily coated, the leather can feel stiff, and cold.

Definition: Chrome tanned leather representing the flesh side of the hide that is split away from the top-grain. It is aniline dyed then a topical pigment coating and clear coating are applied to the surface.  These coatings represent the color and sheen on the leather and have the same chemical composition as a finish on top-grain leather.

Attributes: Because it’s not the top-grain, this leather lacks durability. It’s inferior grade leather without the tensile strength of top-grain, consequently will have a short useful life expectancy. Split-hides are typically heavily pigmented with a heavy urethane clear coat. 

Advantages:  Affordable.  It is fade and stain resistant.  The leather is easy to clean.

Disadvantages: It is heavily coated. The leather feels stiff, and cold.  Splits do not have durability.

Definition: Chrome tanned top-grain leather.  The leather is a called a crust (no finish) with aniline dye infused within the cellular structure of the skin. These are typically the most expensive hides.  Only a small proportion of all leather can qualify to be unfinished as they are the hides with the least amount of unsightly hide characteristics like scaring or other anomalies in the leather.  (See Addendum B.)

Attributes: This is soft, supple leather that has a wonder feel, and look. Aniline dyes are translucent. As such, they accentuate the natural beauty of the leather.   Because it’s the top-grain, this leather has plenty of physical durability.

Advantages:  The initial look and feel of the leather can’t be beat. Warm and inviting, with a wonderful eye appeal this leather represents the best of the best.

Disadvantages: It stains and fades. While it is aesthetically beautiful at the on-set, this leather is vulnerable, particularly in an active household environment.  Very difficult to keep clean.  It is very porous and will absorb body oils, etc more readily.

Definition: Chrome tanned top-grain leather with a light clear coat added for minimal protection.  Like unfinished leather, this leather is aniline dye infused within the cellular structure of the skin. These are typically expensive hides.  Like unfinished leather these are hides with the least amount of unsightly hide characteristics like scaring or other anomalies in the leather. 

Attributes: This is typically soft, supple leather that has a wonder feel, and look. It’s not as soft as pure aniline however, because it has a degree of protection on the leather. (See Addendum B.) Like a pure aniline the dyes are translucent. As such, they accentuate the natural beauty of the leather.   Because it’s top-grain, this leather has plenty of physical durability.   Often a pigment is mixed with the clear coat so there may be a small amount of pigment coating on a semi-aniline as well.

Advantages:  The initial look and feel of the leather is very nice. Like a pure aniline, its warm and inviting, with a wonderful eye appeal.  Because there is some protection it’s not as vulnerable as a pure-aniline. 

Disadvantages: It’s also similarly vulnerable to stains and fades. While it is aesthetically beautiful at the on-set, this leather is vulnerable, particularly in an active household environment even though there is a coating on the leather.  It’s difficult to maintain.  It is porous and will absorb body oils, etc.

Definition: Chrome tanned top-grain leather.  The leather is infused with aniline dye that is “floating” in an oil mix.  This means the dye is not bound to the leather.  Rather it can move inside the hide, showing areas of color loss when stretched, scratched or scuffed.  This leather is often called distressed or referred to as the “bomber jacket look.” 

Attributes: The leather has a certain classic aged look.  Again, the dyes accentuate the natural beauty of the leather, and because it’s the top-grain, this leather has plenty of physical durability.

Advantages:  The look and feel of the leather presents the distressed look that is very popular. The distressing effect helps to conceal stains. Because it’s intended to be distressed, staining and fading are less an issue.

Disadvantages: It does stain and fade.  It is very porous and will absorb body oils, etc more readily.

Definition: Chrome tanned split leather with a very heavy urethane coating.  The leather is aniline dyed. The urethane coating is clear so the color is the dye viewed through the heavy urethane coating.

Attributes: This is typically very low grade leather with little tensile strength.  The primary strength is the urethane coating.  While the initial look is appealing, it has a short life expectancy.

Advantages:  This is low-end leather that is affordable.  It’s easy to clean.

Disadvantages:  Very short life expectancy.  If it fails, it’s not easy to repair.

Definition: Chrome tanned that can be the top grain or split.  This is the flesh side of the leather.  It represents the nap created when the cow hide is split.

Attributes: This leather has a nap to it that presents a soft appearance and feel. It is aniline dyed with no protection. If it’s the top grain turned inside out, then it will have the durability normally associated with leather. If it’s simply the split, it won’t

Advantages: It offers a warm inviting look. Feels comfortable to the touch with a depth of color only a dye can offer.

Disadvantages:  It fades and stains easily. It is very porous and will absorb anything that comes in contact with it. It’s very difficult to clean.

Definition: Chrome tanned, aniline-dyed, top-grain that has been sanded to raise the nap. 

Attributes: Like suede this leather has a nap to it that presents a soft appearance and feel.  It is aniline dyed with no protection.

Advantages:  It offers a warm inviting look.  Feels comfortable to the touch with a depth of color only a dye can offer.

Disadvantages:  It fades and stains easily.  It is very porous and will absorb anything that comes in contact with it.  Like suede, it’s very difficult to clean.

Definition: Chrome tanned, aniline-dyed, typically top-grain leather with a nitrocellulose based finish.  This type of pigmented finish differs from the standard finish in that it is not a continuous film on the leather’s surface.  Rather it’s a scattering of tiny particles that are not connected chemically to each other.  This leather finishing technique is very popular in European tanneries so it is often referred to as a European finish..

Attributes: This type of finish allows for the soft tactile attributes of unfinished to be retained, even though there is a colored coating on the leather.

Advantages:  It offers a supple feel yet still has a finish surface. Feels comfortable to the touch and will hold the color longer than a dye. 

Disadvantages:  Due to the lack of a continuous film, the leather will stain.  This type of finish isn’t as durable as a urethane so it will scratch more easily.