Tanning (or tannage) is the process that turns a rawhide into a leather. This is a process known to mankind for millennia. The earliest evidence of the use of treated leather by humans dates back to around 7,000 BC. For almost 9,000 years, the technology of processing rawhides has remained unchanged. The main role is played by vegetable tannins, which are most often extracted from the bark and leaves of various tree species (oak, chestnut, and acacia). Hence, the name of this type of rawhide treatment – vegetable tanning. Soaking the animal rawhide in tannins lasts for weeks, and in some cases even months.
These tannins also give the incredible aroma of the final leather product, which is an inspiration for many of the most elite perfume brands in the world. The use of natural extracts preserves and even enhances the unique qualities of the leather. The vegetable-tanned leather is a living product. It changes over time. It changes its shape, its shade, its glare. Each product made of vegetable-tanned leather, over time takes the form of its contents. The shoes are shaped on our feet, the wallet – on the credit cards and banknotes, the belt gradually fits better to our waist. Vegetable tanning is also the only process of leather processing that allows it to develop a patina over time or in other words – to enrich the shades of its color, to form a natural wax sheen on its surface.
However, all this has its own price. The whole process of turning the rawhide into a leather suitable for making luxury clothes, shoes and wallets is very time-consuming, laborious and expensive process. The industrial revolution solved this problem by replacing the vegetable tannins with chromium compounds. This allows shortening the processing time of rawhide from a few weeks to several hours. The price is also significantly reduced and the product becomes available to the general consumer. Unfortunately, the innovation goes hand in hand with one huge drawback, namely the toxic effects of chromium on the environment and humans. Chromium compounds are detrimental not only to the water bodies where wastewater is discharged, but also to the people who work with it. The final leather product loses many of its qualities. Tanning with chrome makes the leather softer and short-lived. The leather loses its ability to develop patina.
Nowadays, the processing of leather by vegetable tanning occupies only 8% of world production in this segment. It is concentrated in small family workshops, each of which keeps its secrets about the exact proportions and composition of vegetable tannins, the duration of individual operations, the methods of natural dyeing. Many of these families have set up communities to monitor and improve each other’s product quality and to certify the leather products created by processing their rawhides or skins. One of these organizations is the vegetable tanned leather consortium Pelle Vegetale from Tuscany, Italy.
Because vegetable tanning of the leather is a slow and difficult process that requires a large amount of manual labor, the cost of the final product is very high. This makes this type of leather available only for high-end brands. Vegetable-tanned leather is a material that is completely inapplicable in the so-called “fast fashion”. Products from this type of leather are designed to exist for a long time. The high value of this type of leather is one of the reasons why most such products are manufactured entirely by hand by experienced craftsmen and artisans, passing on their skills from generation to generation.
The leather treated with the tannins from the oak leaves bears the marks of time and fortunately, is still here to present day.