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2020.07.24 Fashion

Tanning leather

Shoes, jackets, belts… so many fashion items use leather as their primary material. And even if it can sometimes be quite complicated to recognise what makes a good leather, the most important thing of all is to recognise what is leather, period! Indeed, the fabrication of leather is a genuine skill, one which goes through many stages, with each one being just as important as the next.

Just after the soaking phase (cleaning the skin), and before the wringing and finishing phases, tanning is the stage that allows a simple hide to become leather. It is a particularly important step that entails a process, more or less slow, that uses tanning agents. Let’s take a look at this crucial step that not many people know about.
How does the tanning process work?
Tanning is an integral part of the overall skill set it takes to make leather, no matter what type of hide is being used. It comes just after the soaking phase, which consists of cleaning the skin of its hairs and diverse residues. As such, tanning allows for taking a hide and turning it into a material that is supple and resistant, and prevents its decomposition. How? By dehydrating it with tannins, whose origins (chemical, natural, etc.) constitute a critical choice during the tanning process. We’ll come back to this. At any rate, the tanning phase itself already sheds some light on the characteristics of different potential leathers: more supple, more impermeable, etc. The soaking and the finishing refine these effects, but tanning is the true first step, in both aesthetic and qualitative terms.

Indeed, it is at the end of this phase that we can affirm if a hide is no longer a hide but a piece of leather!
Tanning agents
Tanning agents are the base of tanning. By affixing them to the hide, they make the skin rot-resistant and prevent organic decomposition. This is precisely the wheelhouse of designers like Alice Balas, who works side by side with tanners in order to make pieces that are as durable as possible, and very often Made in Paris. Nowadays, two principle tannins tend to be used, each with different origins:

Chrome Vegetable tannins.

It should be pointed out that there are other types of tannins, but they make up a minimal part of the market.
Chrome tanning
This type of tanning is the most common all over the world, representing 80% of the market. This process can easily be done in under 24 hours, as opposed to vegetable tanning which can take several months. Practical, economic, multi-purpose; chrome is the method used by numerous fashion brands.

The first step entails dissolving chrome sulfate in water. Using a rotating drum, the liquid penetrates the leather-to-be, and is then affixed to the hide thanks to different ingredients like baking soda. This is called “pickling.” However, even though this approach is the most widely used, its is nonetheless quite harmful to the environment.
Vegetable tanning
Vegetable tanning is estimated to be used by some 10% of the world market. This method, which is longer and costlier, uses plant-based agents like bark, pits, and even mimosa and sumac, among others. These agents are presented in concentrated powders to which oils are sometimes added to develop the suppleness of the leather.

Concretely, the hides used in vegetable tanning are left for 1 - 2 weeks (sometimes longer) in 5 - 8 tanks full of concentrated solution. After a few weeks, the solutions become more and more concentrated, and allow for making the highest quality of leather possible. Hence, one can conclude that using vegetable tanning means that it can take several months to develop the best product.

More and more brands are beginning to switch to vegetable tanning, like Jules & Jenn, Nat & Nin, and Balzac Paris. But there are other ways to transform a hide!
Other types of tannings
Even if chrome and vegetable tanning remain the most broadly used processes, there are other ways of taking a hide and transforming it into leather.

One of these is synthetic tanning, which consists of using synthetically produced agents to reproduce vegetable tannins.

Another type is aluminium tanning which, like chrome tanning, is a mineral tanning process.

Chamois tanning is a little used technique that uses fish oil as its tanning agent.

Combined tanning is a singular technique that combines two different techniques (for example, chrome and vegetable) to make the leather as complete a product as possible. By associating two processes and two types of results, the leather will be more stable and more sturdy.

It goes without saying that these types of processes are more expensive and less mastered than the vegetable and chrome tanning processes, which is why they are not used as much.

Hence, we can see that leather possesses many elements that make it more or less qualitative and more or less durable. And it is quite easy to understand that the type of tanning process plays a role in the overall quality of the final product, so why not give it a second thought?
Photography : Alice Balas / Comme un camion