Leather has been a valuable material for humans forever. It has been used for clothing, shoes, bags, furniture, and other products. But, how is leather made? One crucial step in the process is called tanning, which involves turning animal hides or skins into durable and flexible leather. What is leather tanning? In this post, we will look at leather tanning, the various methods of tanning leather, and its impact on the environment.
What is Leather Tanning?
Tanning is the process of converting animal hides or skins into leather. The primary purpose of tanning is to make the hides more durable, pliable, and resistant to decay. Without tanning, animal hides would quickly decompose, rendering them unsuitable for use. (Which is why leather may not be biodegradable, although it is of animal origin.)
The tanning process involves removing hair, flesh, and fat from the hides, soaking them in a tanning solution, and drying and finishing them to produce high-quality leather.
Leather Tanning Methods
There are two primary methods of tanning: vegetable tanning and chrome tanning.
Vegetable tanning is an ancient and traditional leather tanning method that uses natural tannins (derived from plants) to tan the animal hides. This process takes longer than more modern processes, but produces leather that is durable, firm, and has a unique character. About 10% of all leather is vegetable-tanned.
Chrome tanning is a modern and faster method that uses chromium salts to tan the hides. It’s also cheaper. This process produces leather that is softer, more pliable, and has a uniform color.
Chrome Free Tanning
Chrome-free tanning exists. This is when leather is tanned without chromium. The hides end up with a white color, and are therefore called ‘wet white.’ The manufacturing process, equipment, and results are the same as chrome tanning. There is also a smaller environmental footprint.
The problem is that chrome-free tanning has a very high production cost, which is why it hasn’t been adopted more widely.
Leather Tanning Process
The leather tanning process can take anywhere from a few hours to several months, depending on the type of tanning and the thickness of the hides. It involves these steps:
1 / Soaking
The hides are soaked in water to remove any dirt or salt.
2 / Liming
The hides are treated with lime and other chemicals to remove hair and flesh.
3 / Deliming and Bating
The hides are soaked in an acidic solution to remove lime and soften the leather.
4 / Tanning
The hides are soaked in a solution of tannins to create the leather. Vegetable tanning involves tannins from plant sources, such as bark, leaves, or fruits. In chrome tanning, the hides are soaked in a solution of chromium salts to create the leather.
5 / Dyeing
The leather is dyed with natural or synthetic dyes.
6 / Finishing
The leather is dried, softened, and finished with oils or waxes.
The Environmental Impacts of Leather Tanning
At first glance, leather may seem like an eco-friendly and sustainable material choice. After all, it involves animal byproducts, which are completely natural. However, the process of leather tanning is one that has significant environmental impacts.
1 // Impact of Chromium
The leather tanning process involves the use of chemicals to transform raw animal hides into durable, flexible leather. Chromium, used in the most common method of tanning, is highly toxic to humans and the environment. The chromium used in the tanning process can seep into local waterways and contaminate soil, harming local ecosystems and wildlife. (Remember hexavalent chromium from Erin Brockvich?)
It is worth noting that traditional tanning methods that use natural tannins are eco-friendly, while chrome tanning produces wastewater that can be harmful to the environment if not treated properly.
2 // Impact of Other Chemicals
In addition to chromium, other chemicals used in the leather tanning process include sulfuric acid, sodium sulfide, and formaldehyde. These chemicals pose significant health risks to workers in tanneries and surrounding communities. Exposure to these chemicals can cause respiratory problems, skin irritation, and cancer.
3 // Deforestation
The leather industry also has a significant impact on deforestation. Many of the animal hides used in the tanning process come from cattle ranches that have cleared large swaths of land for grazing. This deforestation contributes to climate change and the loss of biodiversity in these regions.
4 // Animal Abuse
It must be said, the leather industry is directly responsible for the abuse and torture of millions of animals every year around the world. The Food and Agriculture Organization estimates that about 3.8 billion bovine animals are used in leather production each year, (these are 2015 numbers). Most of these animals are raised in horrible conditions, with little importance given to their well being.
Sustainable Alternatives to Chromium-tanned Leather
There are a few ways in which the leather industry can work towards more sustainable operations.
1 / Vegetable-tanned leather
Since vegetable-tanned leather uses natural tannins found in plants, instead of harmful chemicals, it is a more eco-friendly option and is often used by luxury fashion brands.
2 / Recycled Leather
Using recycled leather involves taking scraps of leather and repurposing them into new products. Recycling leather reduces waste and helps to mitigate the impact of the leather industry on the environment.
3 / Ethical Sources of Leather
Finally, the leather industry can work towards more sustainable sourcing of animal hides. This can be achieved through the implementation of better animal welfare practices and a move towards using hides from animals that are raised humanely on sustainable, regenerative farms.
This post was about leather tanning and its impact on the environment
Tanning is a crucial step in the leather-making process. It involves the conversion of animal hides into leather, making them more durable, flexible, and resistant to decay. Tanning has been around for centuries, and there are different methods that are still in use today.
The leather industry has a massive impact on the environment and local communities. There are a few solutions that can be implemented to reduce this impact. By adopting more sustainable tanning practices, using recycled leather, and sourcing hides from sustainable farms, the industry can work towards a more environmentally-friendly existence.
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