Leather production involves a complex process called tanning, which chemically alters animal skin to prevent decomposition. Chrome tanning is a popular method that involves wet blue processing and finishing. Tanneries now recycle liquids and refrain from dumping chemicals to reduce pollution.
The process of turning an animal hide into leather includes a complex series of steps from hide to finished product. These steps are often referred to as “tanning” because of the most distinctive part of the process, which uses the tannic acids found in plant matter to chemically alter the animal skin so it doesn’t decompose or rot. While it’s possible to make leather at home, it’s a smelly and complicated process, so many people prefer to send their hides to large commercial places, called tanneries, to be processed.
Animal skin is made up of three layers: the epidermis, which is the outer layer; the dermis; and subcutaneous tissue, which is a type of fat or fatty tissue. When making skin, you only want strong, flexible dermis, which is partly made up of collagen fibers. Collagen is excreted by cells and forms a network of useful filaments. When leather is processed, these fibers are held in place, while everything else is stripped away.
Chrome tanning
There are various tanning methods, and one common process is called chrome tanning, which is popular because it generally takes less time to complete. The process can be divided into two fundamental phases: the wet blue processing phase and the finishing phase, both of which can be achieved in the tannery.
Completion times vary greatly depending on the size of the hide, the tanning process used, and how busy a tannery is if the hide is sent to be processed.
Wet Blue Processing
Before starting the tanning process, the leather is preserved with salt to prevent it from rotting. When the leather is ready to start working, it is immersed in water to soften it and remove any dirt or salt. A special knife that is built on a roller is used to remove excess meat and fat, and tannic chemicals, such as lime and sulfur, are added to the soaking water to make the water alkaline; this will consume the pet hair. Collagen fibers begin to swell, as excess protein precipitates.
When this process is complete, the water is brought to a stable pH and the swell subsides, so enzymatic cleaners can be added to remove any remaining organic debris. Once the debris has been removed, the hide is pickled in a highly acidic solution, which prepares it for tanning. The tanning agents form bonds with the collagen of the hide, making it resist bacterial attack, and the hides are removed from the wet blue processing vat for finishing, after being run on rollers to remove excess water.
Finish
As the skin emerges from the wet blue stage, it is shaved smooth and even, at which point it is split to the desired thickness. The leather is retanned with different materials depending on whether it needs to be firm or soft, and it is also dyed in the desired colour. After dyeing, the leather is oiled so that it remains supple and supple. Finally, the leather is dried, mechanically treated to make it supple, and buffed so that it has a smooth and attractive surface. At this stage, one option is to emboss the leather with patterns before the final stage, which is the application of a finishing coat of polymer or wax to protect the surface of the final product.
Source of pollution
Leather treatment used to be a highly polluting industry, but tanneries have responded to public outcry over odor and pollution problems. Tanneries now recycle the liquids used in the tanning process and refrain from dumping chemicals. Tanning still carries a strong smell, but in most parts of the world it is no longer accompanied by environmentally unfriendly business practices.
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