What is Vegetable tanned leather?
This is a topic which isn't talked about nearly enough and not something most people know anything about. There's a good chance that if you're interested in Silvermoon and its products, you already are aware of vegetable tanning in some way, but we thought it was still worth bringing up as part of our ethos as a brand.
Leather gets its strength and durability because it has been tanned. Raw hides require quite a lot of work to become leather, such as removing hair and fat, but of particular import here is how it is tanned. Tanning is the process by which a tannin binds to collagen proteins. The purpose here is that it protects the collagen protein, which gives the hide its strength.
What does vegetable tanning mean then?
What makes it vegetable tanning is that the tannins involved are sourced from vegetable matter, specifically tree bark, as has been done for literally thousands of years. The process of milling bark and then tanning leather in pits is very tedious and time consuming. Depending on the tannage it can take between 30 days to 6 months for Shell Cordovan. The alternative, chrome tanning, is a very modern inception, having been invented in 1858, to keep up with the increasing demand for leather. Chrome tanning typically takes about a day. So why use a method which is much more difficult and slow? They yield two very different results.
Advantages of Chrome tanning
The obvious advantage is speed and price, requiring just a day to tan. Chrome tanned leather is typically very soft and spongy and can be split thinner while retaining its strength. Chrome tanned leather is also typically less vulnerable to water and heat. The tanning process allows for chemical dyes to be used allowing chrome tanned leather a very large variety of colour choices. It's typical that people think chrome tanned leather is nicer because it is softer and better looking, at least initially.
Disadvantages of Chrome tanning
Chrome tanned leather does not open up in the way vegetable tanned leather does and thus is not stuffed with waxes and oils and must be coated with a protective layer. It is because of this coating that Chrome tanned leather will not take on any or barely any patina. It will look largely the same regardless of use, which again many people find appealing. However, we objectively think a deep rich patina on an old and well cared for item to be far superior. Chrome tanned leathers do not have the longevity that vegetable tanned leathers have because of the absence of all the oils and waxes and are very prone to drying out and cracking after only a few years. Chrome tanned leathers do not have that classic "leather" smell and typically smell harsh and chemically if not at all, again because of the lack of oils and waxes. Chrome tanned leather also will no biodegrade like vegetable tanned leather does. The chrome tanning process also uses many chemicals which are harmful to the environment when disposed of.
Advantages of Vegetable tanning
Vegetable tanned leather is typically quite dense and robust and is very strong, hence is used for bearing great weight such as in saddlery and industrial uses. Oils and waxes are "stuffed" into the hides after tanning which keeps the leather moisturized and protected. Because Vegetable tanned leather uses plant products to tan, it is much ecologically friendly. The leather will biodegrade when disposed of. There are no top coatings applied to the leather, allowing oils to make their way into the leather forming what is called a patina. There is a wide variety of ways to tan and finishes which can be done. From fully untreated leather with no coating which can take on dyes with well saturated colours and will patina very easily to very waxed leathers with very muted and subdued colours. Though some tannages are able to have relatively vibrant colours and there are still new ones being invented. Finally, it just smells amazing.
Disadvantages of Vegetable tanning
It is very labor intensive to produce and thus expensive. It requires an abundance of water and space for pits to tan. Vegetable tanned leather is typically thick and stiff requiring "break in" which over time will work the fiber structure of the leather to bend in a repeated way. It is because of this stiffness that the leather is not well suited for applications such as clothing or furniture upholstery, though there are some specific vegetable tanned leathers which defy that principle. Depending on the tannage, vegetable tanned leather can be susceptible to water, softening and perhaps even tearing if under load. Some tannages are more water resistant, such as wax stuffed leathers. Vegetable tanned leathers are typically only available in very earthy and subdued colours, the typical being a plethora of browns.
Wild card - Combination Tanned leathers
Recent developments have seen leathers which try to bridge the gap between old world vegetable tanning process and new world chrome tanning processes which miss vital traits of vegetable tanned leather. These are known as combination tanned leathers. Made famous by Horween Leather Company in Chicago they came up with a combination tanning process for their Chromexcel leather.