Among the many types of tanning available on the market, vegetable tanning stands out as the most traditional, natural, and eco-friendly of all. It is called “vegetable tanning” because the raw materials used in the tanning process (i.e., the so-called tanning agents) are tannins, natural substances produced by trees that serve to defend the plant against attacks by external bacteria. These tannins are extracted from various parts of plants, including wood, bark, pods, fruits, and leaves. The most commonly used tannins are derived from chestnut and quebracho wood, Tara pods, and the bark of mimosa and acacia trees.
Vegetable tanning of hides has a very ancient history, dating back as far as prehistoric times: in fact, for millennia, leather processing was a necessity, as hides were a byproduct of meat processing that was difficult to dispose of.
And so, at some point, humans realized that to halt the decomposition of the hide and make it easy to work with, it was necessary to soak it in a soluble solution (based on tannins) that would transform the animal’s hide into leather.
In ancient times, tanning involved finely grinding tree bark, which was then left to act on the hides in a pit after adding water—this dissolved the tannins, allowing them to be absorbed by the hides.
Today, the traditional method of vegetable-tanning consists of what is known as “slow vat tanning,” a long and labor-intensive process that involves immersing the hides in large vats and takes about three months to complete. Thanks to new technologies and techniques refined over the years, a second processing method has become widespread: this is rapid barrel tanning, which, with the aid of rotating drums, has shorter processing times than traditional vat tanning and produces leather that is softer and therefore better suited for use in leather apparel.