VEGETABLE GEGERBTES LEDER

Leather is a raw material that is closely linked to human history. The processing of hides has been known for thousands of years to make clothing, blankets and even shelters. In order to make it supple, to preserve it and to protect it, preservation processes known as tanning have been developed. Classic leather tanning uses a process that uses many aggressive chemicals; this is not the case with vegetable tanning, where the leather is processed in a much more natural way.

Vegetable tanning ensures that the raw material is stabilized and the rawhide becomes a strong, robust and shiny leather. Bark, twigs, leaves and even fruits are used in the stages of the tanning process, which can last between one and three months.

There is a real difference between vegetable tanning and classic tanning, because classic tanning requires the use of chemicals. The method most widely used in the fashion industry today is also the most controversial: it is chrome tanning. Chromium is used in almost 85% of all leather tanning. It is a very aggressive chemical process that is far from the natural look one imagines of the leather used in fashion. The use of chromium salts is extremely harmful to the environment and to humans. Despite this, it is the most common method in the textile industry because the process is faster, uses less resources and, of course, is cheaper. It is also a tanning process that requires significantly less know-how.

We decided a long time ago to use the principle of vegetable tanning as much as possible, even if it is more expensive. Leather is the element that gives the character of a Melvin & Hamilton shoe and with which the brand name is associated. High-quality vegetable tanned leather allows for varied, original and novel shades and colors that you will not find anywhere else. Chemical tanning with chrome kills the properties of the hide and the leather becomes a dead, rigid material without character. While vegetable tanning preserves the suppleness, shine, structure, etc. In other words, the personality of the leather. This natural process takes the time to prepare the hide for a second life and give it perfect strength and durability.

Vegetation is a source of anxiety

Old-tanned leather, tanned leather, tanned leather, vegetable-tanned leather or vegetable-tanned leather are terms for leather tanned in a pit or tanning barrel with oak bark, spruce bark, quebracho wood, tara pods, olive leaves, rhubarb roots, mimosa bark or coffee bean shells. The tanning agent is then a vegetable tanning agent. Vegetable-tanned leather is sometimes also referred to as natural leather.

Vegetable tanning has been around for more than 5,000 years and was the main tanning method for many centuries. From decorations on a sarcophagus, we know that vegetable tanning was known in Egypt in the 4th millennium BC. Thanks to the discovery of Ötzi in the ice of the Alps, we know that around 5,000 years ago, different types of leather were produced for different purposes. There is no exact information about where exactly vegetable tanning originated, as it was developed independently in different cultures. It is believed that various ancient civilizations such as the Egyptians, Greeks, Romans and Indians developed vegetable tanning techniques.

It is assumed that today only 10 - 12% of all leather is vegetable tanned. The cost and quality advantages of the health-damaging chrome-tanned leather have reduced the proportion of vegetable tanned leather to a niche. Before chrome tanning, tanning with vegetable tanning agents was the dominant tanning method. In the niche where vegetable tanned leather has the edge over other tanning methods or where leather lovers prefer this natural tanning agent, vegetable tanned leather is strong and will continue to have its place.

Vegetable tanned leather can usually be recognized by its brown color. Since vegetable tanning dominated long before chrome tanning, old leather in particular is often vegetable tanned. Today, particularly solid leather is still vegetable tanned. For example, for the leather soles of high-quality shoes. Vegetable tanned leather can also be shaped, embossed or punched very well due to its shape retention. Leather can consist of up to 45% tanning agents. Vegetable tanning agents in particular are absorbed more strongly by leather and therefore fill it better, are therefore also heavier and can be better processed into solid leather.

The active ingredient in vegetable tanning is tannins, which are polyphenols of gallic acid. These are stored by the plants to keep away predators whose digestion is negatively affected by tannin intake. Tannins can be found in varying concentrations in very different plants; in addition to the plants already mentioned, they can also be found in wine, chestnuts, hops, sumac, black and green tea. In food, tannins are perceived as dry, rough and furry. For example, the taste of a red wine is fundamentally determined by which tannins it contains and in which concentration. Many tannin-containing plants need up to 30 years of growth before they produce a sufficient amount of tannin. Other plants are richer in tannin when they are still young. There are around 300 different types of plants worldwide that can be used to produce tannin.

• Oak can be used for all types of leather. The bark of younger oak and spruce trees is used because it contains more tannin.
• Chestnut makes a hard and reddish leather.
• Mimosa bark and acacia make leather more flexible and supple.
• Valonea is a Mediterranean, wild oak species that grows mainly in Turkey and Greece. Its fruit cup with tannin-rich scales (also called trillo) has a tannin content of 32%. You can use Valonea Haptik to make soft, firm and tough leather. Leather tanned with Valonea is more lightfast than other plant tanning agents.
• Maletto bark comes from a type of eucalyptus (Eucalyptus occidentalis) found in Western Australia, which grows up to 25 meters tall. The tannin content of the bark is extremely high at 46 - 49%. Since the plant has become rare, the tannin is hardly used anymore.

tannin

Not every plant contains the same amount of tannin. Tannin is primarily a substance that is released when the plant reacts to stress (such as when it is attacked by parasites).

Even within a plant, the tannin content varies depending on the component:

• The bark of oak contains about 10% tannin (in older trees only 5%), and up to 70% in galls. The resulting leather is light brown.
• Spruce bark contains 15% tannin, but spruce wood contains a maximum of 1%. Here too, the leather turns light brown.
• Chestnuts can reach 10% tannin in the wood of old trees. The leather is medium brown and tough.
• Willow bark has 10% tannin and produces yellowish leather.
• The bark of old birch trees contains 10% tannin. The leather is also yellowish, soft, but hard-wearing.
• Valonea has a very high tannin content of 32%. The leather becomes tough and firm.
• The gall apple contains 55-65% gallic tannic acid and the knopper 25-28% tannins. Both are growths on oak trees caused by the gall wasp laying eggs. Tannin-containing growths form around the larva. The countries of origin are Hungary, Yugoslavia and Austria.

The dry matter of the vegetable tanning extracts delivered to the tannery consists of approximately 75% tannins, which are absorbed by the skin to be tanned, and 25% non-tanning agents. Over 90% of the tannins contained in the tanning extract are absorbed by the leather during the tanning process.