Leather is a popular material for creating so many items that has been made for thousands of years. Almost everyone owns some kind of leather item and at some point they are curious about how it is made.
Leather is made from animal skins through a process called tanning. The process is made up of up to 25 steps, which take from days to months depending on the technique used. In addition, the skins can have varied colors, textures and finishes.
It is fascinating how many different techniques are used in the production of leather and the tanning process. It's also amazing how some of the current methods are the same as they were thousands of years ago.
Leather manufacturing can be done in many different ways. Rudimentary tanning can be done by one person, with some knowledge and time. For thousands of years, this was the method used to turn animal skins into leather for shoes, clothing, and tools.
It worked, in simple terms, by cleansing fresh skin and treating it with natural vegetable acids, called tannins. The acids helped stabilize the animal hide from rotting, and also strengthened the material. The skins were dried and the result was a very basic leather.
Vegetable acid tanned leather is still very common today, although the processes to make it have become much more refined and industrialized. But even with those advances, vegetable tanning is a slow process that can take weeks or months to produce a finished piece of leather.
The demand for leather goods has increased over time, so came the demand for a process that was faster than vegetable tanning.
Chrome tanning takes only a few days and allows more control over the qualities of the finished leather. This has made it a preference for the leather goods production industry as they can produce leather faster and to the desired specifications. Chrome tanning relies heavily on chemicals.
In today's more industrialized processes, the chemical solutions used in each step are typically piped or poured into containers that can be emptied through pipes or into nearby drainage areas and then filled with the next solution. This saves the huge overhead of having a container for each step and also saves the effort of frequently moving skins.
We present the following steps that tanneries must do to convert hides into leather:
Raw hides and skins must be preserved to prevent deterioration before the leather-making process can begin. Preservation methods include salting, chilling, freezing, and the use of biocides.
Cured hides or hides are immersed in water for several hours for several days. This allows them to reabsorb any water they may have lost in the curing process or during transport. It also helps clean them of salt and dirt.
It is a method by which wool can be removed from sheepskins using a sulfur-based mixture.
Liming removes the epidermis and hair. This also results in an alkaline swelling of the skin to cause a controlled breakdown of some of the chemical cross-links in collagen.
After liming, the skin is passed through a machine to remove fleshy tissue. Hides can be split into layers at this stage or after tanning.
The main action is to gradually neutralize the alkali of the skin, avoiding rapid changes in pH that could cause distortion or breakage of the tissues.
A prolonged descaler can significantly improve the removal of any limescale, dirt (miscellaneous debris) and residual components broken down during liming. The shake, based on the use of enzymes, completes this process so that the skin is flat, relaxed, clean and ready for pickling and tanning.
Weak acid and salt solutions are used to bring the hide to the weakly acidic state required for most tanning processes. Stronger pickling solutions are used to preserve the hides so that they can be stored or shipped in a stable manner for periods of several months.
Solvents or water-based systems may be used to remove excess oil prior to tanning.
Tanning converts the protein in the raw hide or skin into a stable material that does not rot and is suitable for a wide variety of purposes. The tanning materials form cross-links in the collagen structure and stabilize it against the effects of acids, alkalis, heat, water and the action of microorganisms.
A machine cuts the thicker leather into two layers. The non-surfaced grain layer can be chamoised or have an artificial grain surface applied.
An even thickness is achieved by shaving the leather using a machine with helical blades mounted on a rotating cylinder.
Neutralization removes residual chemicals and prepares the leather for further processing and finishing.
Leather dyeing in a wide variety of colors plays an important role in meeting fashion requirements. Some leathers are only surface dyed, while others require fully penetrated dyes.
Oiling introduces oils to lubricate the fibers and keep the leather supple and smooth. Without these oils, leather will become hard and inflexible as it dries.
The leather is stretched and smoothed. This process also reduces the water content to approximately 40%.
Leather normally dries down to 10-20% water content. This can be achieved in a number of ways and each method has a different effect on the finished leather.
The purposes of finishing are to level color, cover defects, control gloss, and provide a protective surface with good resistance to water, chemicals, and abrasion.
The leather will be classified before shipment to the customer. This classification can consider the intensity and uniformity of color, the feel of the leather, smoothness, visual appearance, thickness, design effects and natural defects such as scratches.
Now that you know the long process that leather must go through to reach your hands in the form of exquisite leather goods, tell us, do you prefer natural leather or do you see no difference between synthetic products? We're sure you notice a huge difference in quality, right?