LITTLE LEATHER PRIMER

The origin of clothing

Contents:

Origin
What is leather?
From the skin to leather
One skin, different types of leather
Grades of leather
Leather care

The beginning

Leather has accompanied humankind since the very beginning. Humans discovered early on the benefits of the skins and hides of the animals they caught for food, turning what was originally a waste product into covers, clothing, shoes, boots, tent walls, straps and belts, and other useful everyday objects to protect themselves against the cold, the wind and wet conditions. Thanks to their knowledge and ability to work with leather and skins, humans were able to survive in even the coldest regions of our planet and defy the natural elements – leather was where clothing started.

What is leather?

Leather is an exceptionally hard-wearing, natural product. Thanks to its very fine network of fibres, leather has an extremely large inner surface compared to its weight (an inner surface of 300 m² weights approx. one gram). This means that it is very resilient to tearing, stretching and flexing, as well as ageing and varying temperatures. Leather is capable of absorbing up to 30% water without really becoming “wet”. Other properties include its natural ability to regulate moisture exchange from the inside out and good thermal insulation.

The skin

The skin comprises a network of exceptionally fine, interconnected fibres. These are not connected in the same way on all areas of the body. Over the back, the structure is more dense and tightly packed, while over the stomach, it is slightly less dense with larger spaces in between. The most valuable part of the skin is the back, which is mainly used for high-quality leather products. Because the skin over the stomach stretches as a result of eating and drinking, it is not as evenly structured as the skin over the back. The area over the flanks is usually stronger with bumps and blemishes (e.g. scars), as the animal is likely to have stood or lain in bushes or hedges while running around.

The skin of mammals comprises 98% protein; the rest is fat, water and minerals. It consists of three layers: the epidermis (forming approx. 1% of the thickness), the dermis (approx. 85%) and the hypodermis (approx. 15%). The dermis is the layer relevant for leather production. The epidermis is formed of a dry, horny layer and an underlying mucous membrane, from which the horny layer is continuously renewed. This is why the epidermis only forms one per cent of the total thickness of the skin. The epidermis is chemically removed in the tannery using slaked lime. The layer of skin of interest to leather production is the dermis, which comprises a dense interweave of tissue fibres, along with blood vessels, hair follicles and nerve endings. The hypodermis is useless in terms of leather production, as it mainly consists of fatty tissues and veins. It is removed prior to tanning during the fleshing process. No two skins are the same. Skins differ from mammal to mammal and breed to breed. Skins also vary according to age, sex, nutrition and the environmental conditions the animal has been exposed to. Furthermore, a skin can exhibit significant variations across its own area. The tanner has to take all of this into consideration during the production process when selecting the grey goods (raw materials) in order to ensure a high-quality leather product.

“Clothing is a ‘waste product’ from the food industry – no animal is slaughtered for its skin.”

From the skin to leather

Leather production is a multi-faceted and complicated process of refinement. A skin is said to pass through roughly 40 processing stages before the biological raw material is finally turned into the natural end product – leather. At the beginning of the leather production process, the skin is prepared for tanning. The first step is to clean the dirty animal skin, which has often been preserved with table salt. Next, all of the parts of the skin that cannot be transformed into leather are discarded.

Chemically, the pelt comprises only the core part of a skin that is to be transformed into leather, the collagen, and it is now ready for the next step – tanning.

The tanning process

In the actual tanning process that now follows, the tannins are allowed to act on the leather to the extent required to achieve the desired and required grade. This transforms the skin into leather, which – unlike the original skin – is resistant to decay and thermal stresses, and can be stored and transported.

The type of tanning method applied determines the intended use of the leather, e.g. for shoes, furniture, clothing or even the automotive industry. While abrasion-resistant shoe soles are exclusively tanned using vegetable tannins, e.g. extracts of chestnut or oak, mineral (chrome) tanning is the preferred method for leather for upholstery, shoe uppers or fine leather. However, chrome-free tanned leather is also increasingly available.

It is the subsequent finishing processes that determine the final character of the leather. These are aided by the use of plant-based, synthetic or even mineral retanning agents. They give the leathers a better and more even fullness and improve quality.

How does the leather obtain its ultimate appearance?

The next stage involves dying, the application of fat liquors to make the leather more supple, and the use of machines to relax the fibre structure. These determine the desired properties such as elasticity or softness. The final finishing process is the drying process. This is a generic term for a series of mechanical and chemical treatments applied to the surface of the leather.

Their main purpose is to achieve the visual appearance and fashionable features of the leather. However, important quality factors such as light and colour fastness can also be significantly improved during the finishing processes.

In the final stage, the various types of leather are given their ultimate appearance.

Different patterns or attractive surfaces can be achieved on the leather by printing or embossing. In other words, it is during the finishing processes that the leather “is given its ultimate appearance and final polish” – as the tanner says.

The main stages in the leather production process

Storage and sorting

The grey goods are stored in chilled rooms.

Softening

During the softening process, dirt and preserving salts are removed from the grey goods, and the original water content returned.

De-hairing and degreasing

In this process involving slaked lime, the hairs are removed from the skin and its fat content reduced to prepare it for tanning. This process has a significant effect on the properties of the resulting leather.

Fleshing and splitting

In this process, the tissues, flesh and residual fat are removed with sharp knife rollers. The leather is split to create a grain leather of a consistent specified thickness. The resulting split leather can be processed further to create e.g. suede.

Acid cleaning, pickling and tanning

In the acid cleaning and pickling processes, acids and salt are used to prepare the skin for tanning. During the tanning process, the skin fibres absorb the tannins. It is this that turns the raw skin into leather.

Withering

The water is now removed from the wet leather by withering.

Sorting

The leather is sorted according to various quality criteria.

Shaving

The grain leather is processed to an even thickness. Uneven areas are removed from the reverse side. The leather is then grouped into dye lots.

Neutralising, fulling, dyeing and fat-liquoring

First, the acids from the tanning process are neutralised. Depending on the type of leather, it is fulled and dyed with water-based dyes. Fat liquors are then added to achieve the softness and elasticity required for the finished leather.

Drying

Two methods are used to dry the leather: vacuum drying, whereby the moisture is sucked out, and festoon drying, whereby the leather travels through drying ovens.

Softening

The extent of the softening carried out by moving the fibres against one another varies according to the type of leather, with particularly soft types of leather undergoing more intense processing than dense types of leather. Different names are therefore given to these processes: STACKING and TUMBLING.

Finishing

In the finishing processes, the leather is given its final appearance. Depending on the requirements of the customer and consumer, the leather is primed, dyed, dressed, pressed and ironed to achieve a glossy or matt, single- or multi-coloured, smooth or grained surface finish. The art of finishing involves applying wafer-thin layers to the leather without impairing the appearance and the prized properties such as suppleness and breathability.

Tanning methods

The description “aniline-tanned leather” is frequently seen. However, tannins are used for tanning. “Aniline” is not a tannin. “Aniline dyes” and “aniline leather” do exist; the “aniline dye” is used to imbue the leather with a particular colour. An “aniline leather” is an open-pored smooth leather, whether or not it has been imbued with an aniline dye. There are, therefore, “aniline dyed” aniline leathers, and aniline leathers that have not been imbued with aniline.

However, this terminology is not easy to understand and often leads to confusion.

Chrome tanning

Over the centuries, vegetable tanning and other tanning methods dominated the tanning process. In 1858, German technologist F. Knapp and Swede H. Cavalin investigated the use of chromium salts as a tanning agent for the first time. The process was then patented in America by the chemist Augustus Schulz. In the following decades, chrome tanning became the dominant tanning method. One deciding factor was the economic advantage in terms of time, it taking fewer days compared to the several months required for vegetable tanning. It has twice the tear resistance of vegetable-tanned leather, whilst being lighter because the chromium salts used for the tanning do not increase the fullness of the skin.

Vegetable-tanned leather

Plant-based tanning has been practised for more than 5,000 years, and for many centuries it was the main tannin method. Embellishments on a sarcophagus are evidence that vegetable tanning was known to the Egyptians in the 4th century BCE. The discovery of Ötzi the Iceman proves that around 5,000 years ago, various types of leather were produced to fulfil various functions. It is estimated that today, only 10-12% of all leather is vegetable-tanned.

Synthetic tanning

Synthetic tanning is frequently used as an alternative to chrome tanning. Synthetic tanning agents (aromatic syntans) are produced artificially, so have no counterpart in nature (carbon and hydrogen atoms).

A disadvantage of synthetic-tanned leather is its sensitivity to the moisture in the leather, and heat.

Chamois tanning

Chamois-tanned leather is known to have existed as early as around 6,000 years BCE. Chamois leather is a tanned leather created by the oxidation of fish oil in sheep or lamb skins whose grains have been split or removed. The leather of dear, goat or cow skin is also often tanned in this way. The most common type of fish oil used is that of the cod.
In Germany, the term “chamois leather” also covers fish-oil-tanned suede leathers of sheep, lamb, buck, deer, chamois, goat, nanny goat and reindeer skin, as well as cow splits. In France and the USA, the term chamois leather is limited to the split leather of sheep skins that are only tanned with fish oil.

Olivenleder

"Olivenleder" and "wet-green" are registered trademarks. The tanning process is patented and protected by the brand “wet-green”. It is also marketed as "O'leaf tan”. Olive leather is tanned with plant-based tannins made of olive leaves. Extracts with a tanning effect are obtained from the olive leaves by extraction and evaporation. The tannin is in liquid form. Olivenleder is generally free of chromium, but is re-tanned using a vegetable or synthetic tanning method.

Napa & smooth leather

Smooth leather encompasses all types of leather whereby the grain side faces outwards. In other words, the upper side of the animal skin is used. Especially soft, chrome-tanned smooth leather is called napa leather. Smooth leather can be semi-pigmented or fully pigmented (aniline leather). The leather will exhibit different properties depending on the depth of the semi-pigmentation. Aniline leather has a significantly more pleasant feel than finished leather. Aniline leather is also considerably more sensitive to sunlight and dirt.

Suede & nubuck leather (rough upper leathers)

Rough upper leathers are all those types of leather whose surface has been roughened up. This gives the leather a velvety character and pleasant feel. This category includes the grain side of smoothed nubuck leather and suede from the underside of the animal skin. Split suede and real suede are not the same thing (real suede has retained the grain side and has been smoothed on the flesh side – in other words, the grain side is worked inwards). Suede is often mistakenly also referred to in common parlance as “buckskin”.

Split leather

When producing the final piece of leather, the thickness of the leather is reduced by splitting. Split leather is the leather from the lower layer of a split skin. This leather is characterised by its two identical surfaces. The upper surface finish can be roughened up, smoothed and coated, or even embossed as required. Split leather is the cheapest type of leather to come from the original skin.

Lambskin (with fleece)

This a special type of suede which has the natural fleece on the inside. The outer side of the suede is coated and smooth. Lambskin often comes from hair sheep with a short fleece, as well as from wool sheep with a greater lanugo content.

A small selection of different grades

Buckskin is the collective term for leather from animals that live in the wild, e.g. stag, reindeer, kangaroo, antelope, gazelle, elk, buffalo, chamois, etc. However, in this day and age, such animals usually no longer live in the wild, but are farmed in captivity. “Buckskin” is not as common, as fewer such animals are slaughtered than cattle, goats, sheep and pigs. These animals are referred to as domesticated animals.

Cow & calf

Cowhide is extremely robust, tear-proof and hard-wearing. Thanks to these properties, it is increasingly being used for hard-wearing and comparably heavy leather clothing, e.g. for motorbike jackets and protective clothing in general. Calfskin, in the classic sense, comes from very young cattle (calves). This leather has a particularly pleasant fineness and feel.

Lamb and sheep

Sheepskin has a similar structure to that of goat leather, but it is not as valuable as it generally comes from sheep breeds that have been bred for wool. There are countless breeds of sheep, whose quality of skin varies significantly. Sheepskin with a strong grain at the neck is referred to as “moutonage”.
The young animal is referred to as a lamb. Lamb’s leather is supple and soft to the touch. The leather is usually processed as aniline leather.

Goat

Compared to other types of leather, goat leather does not contain any fat deposits, making it more robust yet still supple and light-weight. It is therefore more valuable than sheepskin and lighter than many other types of leather. Goat leather is often vegetable-tanned or tanned using a combination of agents and is comparably cheap to produce.

Buffalo

Buffalo and water buffalo leather are usually available as aniline leathers. Buffalo leather has a large-pored skin structure. These larger pores are significantly more visible than those on normal cowhide. The fibre texture itself is also coarser. The individual fibres of the buffalo leather are thicker, but not as tightly interwoven. Nevertheless, it is a strong and robust leather.

Pig

Pigskin is used particularly often in the low-cost leather clothing segment, usually as suede but sometimes also as pigmented smooth leather. Pigskin is less expensive for clothing manufacturers than lamb’s leather. Compared to the more expensive lamb’s and goat leather, pigskin is less tear-proof and usually feels a bit tackier to the touch than the soft lamb and goat leather. When used for clothing, this leather is often referred to as ‘porc’, and the suede as ‘porc suede’.

Deer

Deerskin originates from the hunt and is therefore considered an extremely high-class leather. As it is very soft and renowned for being pleasant to wear, it is often used to produce leather trousers and smooth leather jackets. Today, the majority of this leather comes from farmed animals.

Elk

Every piece has a story to tell. Just like a book, it is possible to “read” the structure of the leather. Blemishes are evidence of biting and fights for food and territory; small scars the signs of insect bites. And the tiny “holes” that look like pin pricks are the natural pores of particularly strong guard hairs. After tanning, elk leather is fully pigmented and not simply sprayed with dye. This retains the natural nuances of colour, the scars and insect bites – consciously preserving the traces of raw nature.

Reindeer

Reindeer belong to the deer family but are farmed in the far north (Alaska, northern Norway, Lapland, Finland, North America and Spitzbergen), often in large herds of domesticated animals. The wild reindeer found in Canada are known as Caribou. The skins of these animals are usually chamois tanned.

Wild buck

Wild buck leather is a somewhat traditional term used for the leather of the wild goat. This fine material has a long tradition in the manufacture of Bavarian traditional dress. Perfectly positioned in the middle, wild buck leather has the elegance of cowhide while being less expensive than deerskin. The chamois-tanned version of wild buck leather is an even more favourably priced (although far from “cheap”) alternative to deerskin. One advantage is the lighter weight of the leather compared to deerskin.

Peccary

Thanks to a life lived in the wild, the leather of the peccary often bears scars and other defects that can be regarded as signs of authenticity. Peccaries are wild pigs from the Amazon. They are medium-sized mammals that belong to the pig family. These animals are 90 to 130 cm long and usually weigh between 20 and 40 kg. Peccaries live in Central and Southern America, as well as in southwest North America.
Peccary leather is used for high-quality gloves due to its suppleness.

Proper care

In this section we would like to give you a few basic rules for handling high-quality leather clothing. Follow these rules and you can’t really go wrong when cleaning and caring for leather clothing. The most frequent mistakes happen during cleaning. However, caring for leather can also lead to some undesired results if the wrong materials are used.

Therefore: ALWAYS find out what type of leather you are dealing with and test out all cleaning or care methods on a part that is not visible (e.g. inside) before applying to the entire item!

Mistakes are most likely to happen when cleaning or caring for open-pored aniline leather (fully pigmented leather) or suede. Particular care should be taken with these leathers. Often water is enough to increase the size of the mark or make it more noticeable. Therefore, always test first whether liquids are absorbed and create large, dark patches (marks).

Surface-dyed smooth leather (semi-pigmented leather) can be treated without any problems using conventional leather cleaners and leather care products. However, it is still necessary to use these with care! A common response is to try and remove marks with a damp cloth or leather cleaner. However, doing this for too long or too intensively can damage the pigmentation of the leather. It is best to avoid the use of products containing solvents where possible, as these can attack the pigmentation of the leather more quickly and tend to make the “damage” worse.

If the mark is fresh or some liquid has just been spilt on open-pored leathers, it is best to apply a cotton cloth (without rubbing) to absorb the liquid before it dries, then dab carefully to absorb any remaining moisture from the leather. This prevents or reduces the likelihood of a clear edge forming. Do not rub at it firmly as this can damage the surface finish. We recommend avoiding the use of special stain removers and other household cleaners. If you think that such products are required, always consult a leather specialist.

Our advice:

Test first (on a hidden area) – then attempt to treat the mark itself. Reproducing the “damage” on the inside of the article and testing the cleaning or care process there first is recommended. In the case of heavy soiling, it is always best to consult a specialist (e.g. the German leather industry association Verband der Deutschen Lederindustrie e.V. recommends LCK leather care products for this purpose). High-quality, open-pored grades of leather are significantly more sensitive to rubbing and liquids. Leather is the oldest form of clothing and over time, items develop a natural, characteristic patina.

A couple of basic rules

Important! Always check whether the leather absorbs moisture or not. Water will penetrate absorbent leathers (aniline leather or raw leather) and will darken the leather when rubbed. Water droplets will run off of non-absorbent leathers (surface-dyed smooth leather). Leathers that absorb moisture are more delicate.
Always carefully test a hidden area (inside, collar) first. With high-quality, aniline-dyed leathers or suede leathers in particular, there is a risk of the spot worsening.
Leather should be impregnated regularly. Despite impregnation, specifically aniline leathers or rough leather upper parts are never fully water-tight and should not be worn in the rain.
Allow leather that has become wet to dry slowly and carefully at room temperature. Avoid any direct heat sources and do not leave it to dry in the sun. This can result in the leather shrinking or drying out too much. After drying, it is a good idea to gently soften or full the leather by working it with your hands.
Garment leather can be washed with suitable leather detergents, but please read the care instructions on the label inside the garment and ensure you use the detergent correctly.
Always carefully brush off any dirt from the surface before starting any care treatments!
Never try to remove any marks that are no longer fresh by rubbing heavily. This can damage the surface of the leather.
Do not try to remove marks with strong solvents (acetone, nail-varnish remover, turpentine, etc.) or with scouring agents, as this will often increase the extent of the damage.
Also avoid using unsuitable products such as shoe polish, cosmetic creams, floor polish, etc.
Your garment will acquire natural signs of use over time. This is normal and part of the patina of a leather, emphasising the natural look of the garment.
Leather clothing must always be stored in a light, airy place. If you are no longer wearing the item, it is best to store it in a cotton or linen clothing bag – leather needs to “breathe”.