This is Part 2 of a five part series on Leather.

In Part 1 of the series, we dove into the significance of leather from a historical point of view as well as looked at the subdivision of leather (areas of the animal hide) and what the 24 most common types of leather are.

The second part of this series will focus on the leather tanning process. At a tannery where leather is processed into its final form, there are four common types of leather tanning processes, which result in: Vegetable-tanned leather, Chrome-tanned leather, Aldehyde-tanned leather, or Rawhide.

What is Leather Tanning?

Tanning leather is an important part of the leather making process as it prevents the hide from rotting and determines the durability and final characteristics of how the leather can be used. When leather goes through the tanning process, its protein chemical compounds are stabilized, which prepares the leather for manufacturing.

Although there are four distinct common tanning methods (each of which creates a different type of leather in texture, durability, and aesthetics), the two most popular forms of tanning used are Vegetable Tanning and Chrome Tanning.

Details of leather wallet by Jozef Jankola

What is Vegetable Tanned Leather?

The vegetable tanning process involves the use of tannins, as well as other ingredients from vegetable matter to tan the hide. Some of these vegetable matters include bark prepared in mills, wood, leaves, roots, fruit, and other similar natural elements.

The process begins with a strong chemical- lime, which burns off all the remaining hair from the hide. Once that is completed, the hide is pickled and put into a barrel of tannin. They are then tanned, dyed, pressed and sorted out.

The colors of vegetable tanned leathers are earthy in rich tones, like brown, olive, and grey hues. They also have a sweet woody fragrance that can remain even with years of use.

Over time, a patina develops on the leather with exposure to sun and the natural environment, which can also give any type of bag made with vegetable tanned leather a particularly unique and appealing aesthetic. When one thinks of leather that gets better with age and usage, the type of leather that’s probably being referred to is vegetable tanned leather.

What are the advantages of using Vegetable Tanned Leather?

The biggest advantage of this tanning method is the sturdiness of vegetable tanned leather and its natural, organic look and feel. Unlike Chrome-tanned leather, which can at times feel more artificial due to its handfeel, smell, and range of possible dye colors, vegetable tanned leather is the closest to the original natural state of the animal hide.

Another benefit to using Vegetable Tanned Leather is that its tanning and production process is more environmentally friendly than other common tanning methods. This is a result of the natural materials used in creating the changes necessary to the hide, like vegetable matters and natural organics.

What are the disadvantages of using Vegetable Tanned Leather?

While Vegetable Tanned Leather is great for creating leather goods that feel more natural, earthy, and environmentally conscious (though some advocates of vegan leather may disagre), this type of tanning method also comes with certain tradeoffs in time, efficiency, cost, and durability.

Because vegetable matters and other natural types of tannins are used in the tanning process, there isn’t much emphasis placed on using non-natural chemicals like water resistance sprays that can help make a bag weather resistant and more usable. Vegetable tanned leather, therefore, does not fare well in any rain, which is why it easily create permanent water drop stains if exposed to a wet environment.

The production process for vegetable tanning also takes about 2 months from start to finish, which is about fifty times longer than creating chrome tanned leather. This increased production time also contributes to the higher cost of vegetable tanned leather.

What is Chrome Tanned Leather?

Chrome tanned leather, also known as “wet blue,” is the most common type of leather tanning method due to its cost, efficiency, and versatility. 85%+ of bags that feature leather are probably made with chrome tanned leather, since this type of leather is far more pliable and supple than vegetable tanned leather. While some bag shapes and folds might be impossible to make with vegetable tanned leather due to the leather’s sturdiness, with chrome tanned leather, there’s much more room for creativity in bag making.

With the chrome tanning production process, leather hides are soaked in acidic salt baths before being treated with chromium agents, hence the name ‘chrome tanning’. The chemical reactions between the chromium agents and the leather hide create a blueish color during the process, which is also where the nickname ‘wet blue’ stems from.

Seeing is Believing by Carlos Caicedo

What are the advantages of using Chrome Tanned Leather?

One of the clearest benefits of the chrome tanning process is that it’s cheaper and more efficient than vegetable tanning. Tanneries that up to date technology and equipment can complete the entire tanning process in as fast as a day, compared to the average sixty days that it requires to tan and dry vegetable tanned leather.

Many brands that use chrome tanned leather are therefore able to purchase leather at a lower price than that of vegetable tanned leather, which often results in more affordable and lower costs for consumers purchasing their bags or other leather goods.

The versatility of chrome tanned leather is also unmatched compared to other tanning methods. With chrome tanned leather, a wider range of dyes can be used, from simple shades of black to more esoteric colors, like blue or yellow.

Versatility also extends to shape and form structure, which means that a bag that requires more complex folds, like a handbag, or uniquely shaped backpack, can be made with the supple and pliable nature of chrome tanned leather, whereas with the much stiffer vegetable tanned leather such shapes likely wouldn’t be possible. The same type of versatility can be said when chrome tanned leather interacts with water as it does not discolor or lose its shape as drastically as vegetable tanned leather.

What are the disadvantages of using Chrome Tanned Leather?

The main drawback of this tanning method is the possible harmful effect that the manufacturing process can have on the environment. While vegetable tanned leather involves vegetable tannins and other organic and natural sources, chrome tanned leather involves synthetic chemicals like chromium that can potentially be pollutants in the air, water, and soil.

If the natural brown finishing and earthy smell and aesthetic of leather is something that is sought after, then chrome tanned leather can at times come off feeling too manufactured and artificial.

What is Aldehyde Tanned Leather?

Aldehyde Tanned leather, also known as wet white, involves the use of glutaraldehyde and oxazolidine compounds. When the leather is tanned with these chemicals it turns to a white color, and its applications can mainly be seen in car interiors and shoes for infants.

Even compared to chrome tanned leather, aldehyde tanned leather is a quicker method of tanning; the white color makes it easier to dye and the leather it results in is water absorbent, soft, and machine washable. This kind of cost efficiency and durability gives aldehyde tanned leather an advantage over the other two tanning methods mentioned, which is why it’s often seen in car interiors and shoes for infants.

Similar to chrome tanned leather, aldehyde tanned leather involves a chemical process that can also be damaging to the environment.

What is Rawhide Leather?

Rawhide is made by soaking thin skin into lime and then stretching it while it is dry. The result is a stiffer and more brittle type of leather compared to the other 3 forms mentioned.

The applications of rawhide leather are most commonly seen in things like leather shoelaces, or tools like a sling shot, since these objects rely on leather being very sturdy and stiff in order to function as designed.

Conclusion

In this second part of our four part series diving into the world of leather, we examined what are the common tanning methods and how each tanning method creates a unique result in the look, feel, and utility of the leather.

The next part of the series will examine the classification of leather and the different types of quality and grade, like what the difference between full grain and top grain leather is.


Everything You Need to Know About Leather Series

Part 1: How is Leather Made & What Are Common Leather Types?

Part 2: Vegetable Tanned Leather or Chrome Tanned Leather?

Part 3: The Grades of Leather & What They Mean

Part 4: Why is Full Grain Leather Considered the Best of the Five Types of Leather?

Part 5: How to Care For Your Leather Bag