The process of producing leather is called tanning. With the use of natural or mineral materials the structure of the hide is stabilized so that it becomes durable. The history of Corf bags goes back to a tannery founded in 1842.
The living circumstances of the cattle determine the quality of the leather
The quality of leather depends on the quality of the hides and thus on the living circumstances of the animals. The best hides come from animals living in regions with a moderate climate and continuous availability of food and water. Such areas are for instance southern Germany, Switzerland, Austria or Bihar in the North of India.
The quality of hides is more even if the animals live in a controlled pasture. Hides from cattle living free on big farms in South America may show an uneven structure due to the changing conditions of the climate.
The preparation for tanning
Normally hides are kept in storage for a certain time before the tanning process can start. To prevent putrefaction, they must be salted. Later the first step in the tannery has to wash the hides and eliminate the salt.
Afterwards the hair is removed, and the skins are cleaned by a machine with a rotating cylinder with blades.
The original thickness of a hide is 3-4 mm. For leather bags normally only a thickness of 1.2 to 1.8 mm is needed. Therefore, the hides are split into two or even three parts. The upper part has the even surface as condition for the good look of the leather and the tearing resistance required for the production of a business bag.
Tanning means eliminating putrefying ingredients from the hide and adding vegetable or mineral agents to make the hide durable and elastic. Till the end of the 19 century tanning agents consisting of leaves or barks were used. The content of the tanning agent can vary from approximately 8% in the bark of oak trees to 30% in the bark of Mimosa.
The choice of the tanning agent determines the look and the strength of leather. Vegetable tanned leathers have a slightly brownish tan. For our Hunting series the leather will get a light anillin finish so that the structure of the skin remains visible and the bag will get a beautiful patina during use.
Vegetable tanned leather is less flexible. For soft shoulder bags and purses the touch of the leather is important. This leather will be tanned by using chrome sulfate. Chrome tanning substituted vegetable agents at the end of the 19nth century. Nowadays tanners often combine vegetable and chrome tanning to reach the softness and elasticity required for the final product.
The tanning agents must penetrate through the full substance of a hide to achieve a good quality of the leather. Vegetable tanning took up to three months as long it was done in pits.
In the beginning of the 20th century tanners started using rotating drums. The movement of the hides in the drums accelerated the penetration of the tanning agents, so that in combination with the use of chrome sulfate the process could be reduced to two or three days.
Tanning in rotating drums
The tanning in drums today is often combined with dyeing (see below).
Coloring and Finish
The final stages of the tanning process decide about the characteristics of the leather and depend on the kind of product for which the leather will be used.
- Leather for belts or saddles should be strong and durable,
- Leather for bags should be soft, but also have a "body" – meaning a bag should keep its shape
- Leather for clothes should be very soft.
The dyeing is important for the quality of a leather bag.
For top grade leathers the natural look of the skin should remain visible even after the dyeing. For this purpose, anillin colors are used which allow to see the structure of the surface. If the quality of the skin is very irregular and the surface rough pigment colors are applied. These will cover small defects and irregularities.
Pigment dyes also protect the surface of the leather and may make it water repellent. But a pigmented leather also loses the natural touch. So, in most cases the dyeing is done combining anillin and pigment colors. The more even look of a leather pigmented leather makes cutting easier and also the assembling of the components of a bag.
Coloring of leather with a spraying machine
Corners, handles and the bottom of leather bags are first to show signs of use when the color has been worn out. This is less visible if the leather has been dyed through in the drum.
After the dyeing most leather is slightly printed. This also helps to make the surface more even. Using pigment colors and printing the leather will lose some of its elasticity. To restore the softness the skins will be milled in rotating drums.
Also check our article "Leather colors and finish"
Leather is natural and sustainable
Hides are by-products of the meat production. Animals are kept because of their meat. Hides are left over, and by tanning they are transformed into a valuable material. For centuries leather has been used for many items meeting the basis needs – from clothes to belts, shoes and bags.
Modern technology helps to control any negative impact on the working environment during the tanning process. The sustainability of leather is based on the fact that it is a natural product which has not to be produced by chemical processes based on crude oil.
Unlike artificial leather or nylon no resources as crude oil is required.
Also, the chemical and organic compounds required during the tanning process nowadays are disposed or reused in a way avoiding any pollution.