Ledergerbung
How does a tanning process for leather goods work
Ledergerbung: Wie funktioniert ein Gerbverfahren für Lederwaren
Leather tanning is the crucial step in leather production , which preserves the raw, perishable animal skin, transforms it into durable leather and gives it flexibility and a pleasant feel. There are different processes for this transformation. These include the so-called "real tanning", which includes vegetable leather tanning and chrome tanning. Alum tanning and tanning with fat, for example, are classified as "fake tanning".
A leather manufacturer usually buys the already tanned leather hides for further processing. The pure raw material, the animal hide, is initially a perishable, organic product. Only through processing does the raw material become a resistant and durable end product that can be made into a leather bag, shoes or a leather couch. This transformation requires a complex processing process that - depending on the type of leather and tanning process - takes several weeks to months.
WHAT HAPPENS DURING LEATHER TANNING?
The most common tanning methods are chrome tanning and vegetable tanning, which are often combined with each other or with so-called synthetic leather tanning.
During the tanning process, the animal hide is transformed into more resistant and less perishable raw leather by adding various process chemicals. The tanned leather is then used in the subsequent manufacturing process, for example in the clothing or automotive industry.
The main tanning process primarily makes the leather durable. Other desirable characteristics, such as special softness, dyeability and grain resistance, are added to the already tanned leather through the retanning process.
WHAT TYPES OF TANNING ARE THERE?
There are a variety of tanning processes, some of which are very old. Not all of them are suitable for industrial use. The most important tanning methods can be roughly divided into "real tanning" and "fake tanning".
"REAL TANNING":
During the tanning process, the skin fibers and tanning agents form an irreversible, permanent bond. The real tanning process makes the leather particularly durable.
mineral tanning, especially chrome tanning
75 - 80% of leather worldwide is tanned with chrome. German and European tanners generally work under strict conditions and can guarantee that the chrome-tanned leather is of a quality that is harmless to health.
Vegetable/vegetable leather tanning
Here the leather is tanned with oak or spruce bark, quebracho wood, tara pods, olive leaves, rhubarb roots or mimosa bark. If you value sustainability, you should also pay attention to the origin of the tanning agents, because vegetable tanning is not always more sustainable than chrome tanning!
Synthetic leather tanning
Synthetic tanning agents are artificially produced and usually used in combination with mineral or vegetable tanning. Leather that is only synthetically tanned is very sensitive to moisture, heat and UV radiation.
"FAKE TANNING":
These types of tanning create an unstable bond between leather and tanning agents, which can easily be disrupted by environmental influences such as heat or moisture.
alum tanning
Dyeing with aluminum salts produces a whitish colored, very sensitive leather.
tanning
Leather tanning with fish oil is considered to be the oldest known tanning process. During a production period of three to four months, the oxidation of the oil produces leather with a yellowish color.
WHICH TANNING TYPE IS THE MOST COMMON AND WHY?
Chrome tanning is still the most common method for tanning leather because it is the most time-saving and, according to Andreas Meyer, Managing Director of the Association of the German Leather Industry , it is not as bad as its reputation.
"Many people are afraid of chrome-tanned leather because it is said to be harmful to our health," he explains, "but in fact there are no statistics to support this."
Chromium 6 is highly toxic in liquid and gaseous form and should never be inhaled or swallowed, but it is converted into chromium 3 through proper processing with appropriate reducing agents, which only takes place in German tanneries. "Anyone who is sensitive to leather treated in German tanneries either has a chromium or leather allergy," says Meyer. However, the leather is certainly not dangerous to health.
WHICH TANNING METHODS IS MOST FRIENDLY FOR OUR ENVIRONMENT?
Vegetable tanning of leather does not require any chemicals, but chrome tanning is much more effective and saves time than vegetable tanning. "That is why, contrary to its reputation, chrome tanning is sometimes even more environmentally friendly than vegetable tanning," says Andreas Meyer. According to the expert, vegetable tanning, which is much more complex, uses a lot of energy and in order to achieve the leather properties desired by consumers, such as a soft feel and UV resistance, chrome often has to be used in the retanning process. "German tanners now work with such good wastewater technology that chrome tanning can definitely hold its own against vegetable tanning in terms of sustainability," says Meyer.
WHERE DO THE SKINS THAT ARE PROCESSED IN GERMAN TANNERIES COME FROM?
Not only the tanning process, but also the origin of the hides that are processed into tanned leather play a role. A large proportion of the hides processed by German tanners are of European origin. According to Meyer, southern European bull hides are particularly suitable for processing in the furniture or car industry due to their large surface area. Northern German bull hides are popular for accessories and the clothing industry. "At our German companies, traceability to the slaughterhouse can always be guaranteed," promises Andreas Meyer. This means that you always know exactly where the processed animal hide comes from. Of course, this is not always the case with foreign companies.
If you value sustainability, fair working conditions, animal welfare and quality, you can get leather tanned to high standards from German tanners that meets our health standards and our demands for high quality and durability.
HOW MANY TANNERS ARE THERE LEFT IN GERMANY?
"The profession of tanner has a disreputable reputation in this country," regrets Andreas Meyer, "most young people prefer to sit behind a desk."
But it is a craft rich in tradition that is often passed down within the family. What is striking is that there are few dropouts. "Once you start tanning, you never stop," laughs Meyer, "that's saying something!"
In Germany, the tanning process is subject to strict regulations that protect animals and humans and ensure the quality of the leather. "These regulations are important," explains Meyer, "but meeting them has become almost impossible for smaller (family) companies." This is why tanners often join together to form larger associations. Today, there are still around twelve larger tanneries in Germany with over 50 employees. In order to produce more cheaply, many companies have their leather tanned abroad. However, German tanners can usually guarantee better quality and environmental standards. This is why it is worth investing in leather products that have been tanned in Germany or Europe.
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