Definition of Vegetable Tanned Leather
When we talk about vegetable tanned leather, we are referring basically to a raw leather, generally bovine or sheep, which has undergone a chemical transformation (called tanning) which is characterized by the fact of using only substances that are found in nature, such as tree barks or flowers (the so-called tannins). The purpose of tanning is to make animal skin (putrescible material and in its raw state not usable) rot-proof and usable for the creation of tools and objects useful to man.
Vegetable Tanning: Features
Vegetable tanning is one of the oldest methods of leather tanning and consists in transforming a raw animal skin into a material that respects its original characteristics as much as possible, using, as chemical reagents, only substances found in nature (in particular in the bark of some trees) called tannins. The so-called "vegetable tanned leather" derives from this complex transformation process.
Vegetable tanning is a natural process that respects the animal and the environment and exploits the substances present in nature to give unique characteristics to the leather. Furthermore, this process takes place without upsetting the leather and without treating it aggressively. Finally, we would like to underline the fact that the raw hides used for tanning are a recycled material as they derive from cattle and sheep raised not for their skin but for the food industry. This aspect means that no animal is killed in order to benefit the tanning process.
For all these reasons, vegetable tanned leathers not only do not contain toxic substances that are harmful to humans and the environment, but are also usually well tolerated by people allergic to heavy metals.
History of Vegetable Tanning
Vegetable tanning has very ancient origins, some examples of natural tanning date back to 2000 years ago even if the greatest development took place during the Middle Ages and until the end of the nineteenth century almost all leathers were vegetable tanned.
This process is based on the use of water and a class of tanning reagents contained in the bark of different plants (such as oaks, birches, chestnuts and acacias, etc.) commonly called tannins. In the past, vegetable tanning was a very slow process and required the hides to be tensioned with a loom and immersed for 1-3 months in a solution of water and tree bark, frequently checking the tanning state. Furthermore, the leather tanned in this way was not very flexible and was generally used for shoes, bags and belts. Over the centuries the expert master tanners have jealously handed down, from generation to generation, the secrets of this precious artisan process, which today has become a perfect mix of ancient recipes and advanced technology.
Until the sixties, vegetable tanning took place in tanks (slow tanning in tanks), in which the hides were immersed in solutions of tannins at progressively increasing concentrations and lasted about 30 days. Today the so-called rapid tanning in drums is mostly used which, thanks to the movement of rotation and flapping, allows to obtain a more flexible leather and to reduce tanning times which are between 36 and 48 hours.
Tannins in Vegetable Tanning
Tannins, as anticipated, are the tanning agents that characterize the vegetable tanning, they are obtained in nature mainly from the flowers and the bark of the trees. The use of tannins, available in both liquid and powder form, is therefore one of the foundations of vegetable tanning as it gives that unique feature that makes the treatment immediately distinguishable.
According to the International Glossary of Leather Terms, vegetable tanning is: "Leather tanned exclusively with vegetable tanning materials or with said materials and the addition of small quantities of other ingredients used only to facilitate the tanning process or to improve or modify tanned, but not in quantities such as to significantly alter the essential characteristics of the product's vegetable tanning".
Vegetable tannins are phenolic substances contained in trees or flowers with different concentrations, they take their name from the plant from which they are derived, we will therefore speak of chestnut tannins, sumac, quebracho, mimosa, oak, etc. All the tannins give the skin a more or less intense brown color and a different flame depending on the plant of origin. The mechanism according to which they bind to collagen to give the tanning is completely different from that of chromium, in vegetable tannins it is a hydrogen bond that is established between the phenolic groups of the tannin and the peptide groups of the collagen. Finally, the amount of tannins used varies greatly according to the product to be made, ranging from 15-20% for small leathers intended for lining or small leather goods, to 40-50% for sole leathers.
The vegetable tanning treatments, besides being absolutely natural, have the great merit of giving the product traces of lived, a very high quality that allows an aging without ruining the product. It also allows, through a careful choice of tannins, to obtain warm leather tones that tend to resurface over time. Choosing a product made with leather from vegetable tanning means owning an article that is the expression of an ancient unique philosophy.
Vegetable Tanning Production Steps
The vegetable tanning processes is quite long and complex and can be divided into two broad parts: "wet" processing and "dry" processing. The "wet" processing includes all phases where the water is involved, instead the "dry" processing refers to the finishing stages. The whole tanning process is made of 5 macro-phases:
- Riviera works
As anticipated, all tanning processes require continuous use of water and since prehistoric times the processing was carried out near rivers. The processes with water, or wet, begin with the so-called riviera phase, from the French "riviere" (river), precisely because until the last century they were actually carried out along the waterways. This preliminary phase has the purpose of preparing the leather for the next phase and is almost the same in the two types of tanning: the mineral one, with metal salts (mainly chromium salts) and the traditional one, vegetable tanning. The preliminary stages of tanning process, also called "riviera works" are:
- Hair removal
Once the riviera phase is over, the leather is not yet tanned, but it already has a certain degree of stability that allows it to be preserved for a certain period of time. Here the paths between mineral and vegetable tanning are clearly separated, since different products are used, even if the goal is in any case to prevent the deterioration of the leather by stably fixing the different tanning products: vegetable tannins, of natural origin, in the case of vegetable tanning process and the salts of some chemically produced minerals in the case of chrome tan process.
Subsequently, the tanning and re-tanning phases begin: at these stages the leather is tanned with water mostly in large barrels, called drums, which by rotating facilitate the penetration of tanning products, fat-liquors and any dyes. Once tanned, the leather is obviously still damp and with the drying begins the fourth phase, that of dry processing and finally we have the various phases of product refining, based on the requirements to be obtained.
In reality, once dried, vegetable tanned leather needs few refining processes, simple mechanical operations are enough to soften and stretch it, and then it can be immediately used for the production of finished products. If it is not even colored, it retains the original colors of the peel of the plants used: it goes from a light beige color using the various types of mimosa, to a more reddish brown beige with the use of quebracho, up to a more intense brown with the use of chestnut peel. Often a "cocktail" of the various tannins is made to get what you want.
Advantages of Vegetable Tanning
The main advantages of vegetable tanning are:
- The use of only natural substances in the tanning process
- Each skin is different from the other and has characteristics of uniqueness and un-repeatability
- It is suitable for people with allergies
- It has an almost zero environmental impact
- Unique and unmistakable smell
- It is easily customizable with the most varied techniques: engravings, prints, colors, etc.
- It reaches high thicknesses, up to 6 millimeters, which other tanning cannot reach
- Greater resistance and durability, the skin does not age but improves over time
- It is eco-sustainable
- It is an excellence of "Made In Italy"
- Higher selling price than other treatments
- Added value perceived by the end customer
Disadvantages of Vegetable Tanning
Instead, among the main disadvantages we have:
- Length and complexity of the manufacturing process
- More expensive production raw materials
- Higher process cost
- Difficult to standardize
- More limited range of colors
- Natural sings and differences between one leather and another are present and often confused with leather defects when in reality they are an added value
Where to buy vegetable tanned leather?
Buyleatheronline.com is the biggest online leather supplier with a worldwide shipment service at affordable rates. On our website you will find plenty of kinds of vegetable tanned leather hides for sale and skins suitable for the production of quite every item: from the the leather for belts to the finest Italian veg tan shoulders for perfect bags and accessories. Moreover, if you are a passionate of tooling, carving and engraving, you will find the most suitable kinds inside the dedicated category to Leather for tooling, carving & engraving.
All our leathers are produced and tanned in Italy, which represents a guarantee of quality and environmental sustainability, as the Italian tanning sector follows the most stringent pollution standards and guarantees that the leather is 100% eco-sustainable.