tanning

TANNING REFINED: RAW HIDES ARE BECOME LEATHER
Recourse to tanning processes that are thousands of years old serves health and the environment

Vegetable-tanned leather as the basis of a holistic, ecological approach to shoe production.

From waste product to valuable raw material

The early people had to make great sacrifices and constant efforts to extract food, aids and materials from the harsh nature in order to survive. The prey was therefore utilized as completely as possible: our ancestors learned to produce valuable and useful clothing and equipment from the fur and skins of the animals, which were actually initially waste. To do this, they had to develop methods to make the fresh skin of slaughtered animals, which was quickly perishable and at risk of putrefactive processes, durable and usable - tanning is what turns raw hides into sought-after, versatile leather.

Apparently, people initially learned that simply drying the skin alone doesn't help and only results in a hard, brittle consistency. Smoking and chewing the raw material was the first successful approach to preservation - and at some point it was discovered that vegetable substances could be used for methodical tanning with better quality. This ultimately gave rise to a craft: Tanners in antiquity and later in the Middle Ages used pits in the earth into which the hides were sunk together with a decoction of fats and suitable plant substances over a long period of time, often many months. The finished leather then served as a valuable raw material for other crafts to produce equipment, accessories, clothing or shoes.

Natural leather goods based on vegetable tanning

Natural goods manufacturers not only rely primarily on vegetable tanning for leather products, but also take a holistic approach to material extraction, processing, use and disposal. An important approach is to shorten transport routes in order to avoid painful delivery conditions for the slaughtered animals and to be able to dispense with the preliminary preservation of the raw hides. For this purpose, cooperation with agricultural businesses that are committed to species-appropriate husbandry is sought. In addition to ethical considerations, there are also very pragmatic reasons to avoid factory farming and improper animal transport, as these leave traces in the animal skin: the leather quality suffers due to large-scale wounds. In contrast, the skin of animals kept in a species-appropriate manner shows other, specific characteristics such as scars from thorns or insects, which makes this skin unmistakable and gives the products made from it an individual touch.

When using traditional tanning processes, barrels or pits with plant extracts are used, which should come from renewable sources - such as the fruits of the Peruvian Tara tree or the Turkish Valonea oak. In both cases, the trees remain intact after the fruit is harvested. The tanning process, which can take 20 to 30 months, is based on the release of tannins, which have a preservative and antiviral and antibacterial effect. The leather resulting from such tanning has the typical bitter smell and feels soft.

Chemical industry: increasing efficiency – but also risks

With the emergence of the chemical industry in the middle of the 19th century, the tanning trade also became a separate industry aimed at efficiency. The use of chromium salts brought with it an unimaginable increase in productivity: since then, the tanning process no longer took weeks, months or even years, but within just a few hours, a foul-smelling raw material that was at risk of decomposition was transformed into a valuable material. This progress almost caused the old plant-based tanning methods to be forgotten. Today it is estimated that less than 20 percent of the leather used in clothing production still comes from tanning processes using purely plant-based materials.

In addition to advantages, progress also brought problems - above all, chrome tanning, which now dominates the global market, can cause risks for people and the environment along the entire process chain. The wastewater from such tanneries is enriched with dangerous substances, including salts and heavy metals, which can kill microorganisms and also larger living beings.

Chromium III or Chromium VI – an existential difference

For chrome tanning, chromium III salts are used, which are comparatively harmless - at least compared to chromium IV (so-called chromate), which is considered a thousand times more toxic. If chrome tanning is not carefully carried out and monitored, the intentionally used chromium III can produce the undesirable and very dangerous chromium VI, which is said to have allergenic and carcinogenic effects.

The disposal of the waste generated during processing and the leather products after the end of their useful life is also seen as problematic. In particular, in Germany it is important to dispose of tens of thousands of tons of old shoes, jackets and upholstered furniture made of leather containing chromium every year in such a way that the environment is not harmed as much as possible - because burning can also produce chromate.

Strict environmental protection in Germany: Tanning abroad to circumvent this

In Germany, tanneries have to comply with legally defined limit values ​​- this means that environmental damage caused by chrome tanning can be limited with the help of highly developed wastewater technology. However, the strict local environmental protection combined with relatively high labor costs has an impact on the price of the finished leather, which is why tanneries abroad are largely used, especially in the so-called Third World. This means that most of the raw hides produced in German slaughterhouses are exported - the finished leather is then imported again.

In the leather-producing countries of the third world or in the so-called emerging countries there is usually a lack of sewage treatment plants, so that toxic wastewater is discharged into bodies of water without being filtered and threatens to poison the groundwater. Wells can therefore become permanently unusable: agriculture and the people living and working in the area are damaged, as is their environment. Furthermore, there are hardly any occupational safety regulations there - even children often have to work long, hard and for little money under undignified and dangerous conditions. Even basic protective equipment such as breathing masks or gloves are usually missing. As a result, many suffer from allergies, metabolic, respiratory or skin diseases.

Rawhide export and customer expectations: Additional use of harmful substances

In order to protect raw hides from decomposition, particularly as a result of mold and rot during longer transport, preservative substances must be added to them in advance. In Europe, salt or brine is usually used to bind the water from the still wet skins - but this then has to be washed out again. The over-salination of wastewater in the regions concerned also poses a serious ecological challenge.

Preservatives that are considered dangerous, such as trichlorophenol or tetrachlorophenol, are used for ship transport to more distant destinations. Once they arrive at the tannery, the raw hides must first be freed of hair and meat residue, for which many different chemicals and soaps are used.

Customers' high expectations of the color and structure of the leather also require the use of additional chemicals for surface treatment - including the coating. This means that the actually breathable leather is sealed with the help of substances that are ecologically and health-threatening. The only examples that are mentioned here are polyurethane, acrylic resins and fluorocarbon compounds.