When we talk about tanning leather, we don’t mean leaving it out on the beach to get browned in the sun. Tanning is the process of turning an animal hide or skin into durable, usable leather. Once the animal skin has been stripped of its fur and degreased, the water needs to be processed out of it, or it will start to rot. However, draw the water out too fast and you wind up with a dry, brittle skin, basically useless for making stuff.
Enter tanning: the ancient process stops the decomposition of organic material (and we’re talking centuries old ancient – there’s evidence that neolithic civilizations in Pakistan were tanning leather over 5000 years ago!). It also determines the quality, durability, and look of the material that makes up all the best boots.
There are plenty of ways to tan leather but in the world of boots you’re usually looking at one of two methods: vegetable tanning, which is how humans have been doing it for centuries, and the relatively modern process called chrome-tanning. Which is the best bet for your boots? Let’s take a look.
What Is Vegetable Tanned Leather?
Vegetable tanning, also known as veg-tanning, uses vegetable matter like roots, leaves, twigs and bark which are high in a compound called tannin (not coincidentally where the process gets its name) that dehydrates the skins by replacing the water molecules and bonding with the collagen. Hides are stretched out on wooden frames and soaked in vats of increasingly concentrated tannin compounds, eventually resulting in a flexible and durable leather.
Here’s the downside: vegetable tanned leather takes time to produce: usually somewhere between 30 and 60 days. And, in addition to the time commitment, vegetable tanning also requires the careful attention of a craftsman. Both these factors mean that this kind of leather comes with a heftier price tag.
The good news is that higher price is worth it — veg-tanned leather can last for years, even decades of heavy wear. And while this kind of leather can feel a bit stiff out of the box, it ages beautifully, acquiring a natural patina, and over time it molds to the foot and softens up without cracking.
Leather after chrome tanning. Photo courtesy of Horween Leather Company.
What Is Chrome Tanned Leather?
Chrome-tanning, veg-tanning’s younger, faster cousin, replaces all the organic stuff with a man-made compound called chromium(III) sulfites. And ever since they were discovered in the 1890s, something like 90% of all the world’s leather is made using this method.
Why? Speed, of course. The process takes only a day, and results in a greyish-blueish, semifinished leather which is stretchier than its organically processed counterpart, in addition to being much easier to produce. The leather is then waxed, oiled, shaved, lubricated, or dyed to produce the finished product. Chrome-tanned leather is easy to dye, and holds color well over the lifetime of the piece.
So overall, it’s a quick, cheap, easily automated process that results in a thin, colorfast and supple leather — so what’s the downside? Well, for one, chrome-tanned leather can have a shorter lifespan. The chrome process is quick because the chemicals involved literally dissolve out parts of the hide, which makes the final product thinner, but means cracking and wearing out can happen more quickly. Plus, very cheap chrome-tanned product can come with a weird chemical odor that lingers for a long time.
Aside from the leather itself, there’s also the environmental impact of the process to consider. What do you do with the (distinctively, disturbingly blue) vats of chromium water when you’re done with them? Many tanneries just dump them into local water sources, leading to contamination of drinking water and a whole host of health problems for the people who live nearby. Take, for example, Kanpur, India — considered the leather capital of the world for the high concentration of tanneries there — where respiratory problems, renal failures, dermal issues, and birth defects have become the norm.
Viberg vs. Alden, boots often compared because they both use high quality Chromexcel.
Combination Tanned Leather
If you’re wondering, “Isn’t there a way to get the best of both worlds?” then you might want to think about veg-chrome combination tanned leather, which uses elements of both processes. Far and away the most popular veg-chrome hybrid is Chromexcel®, a leather devised by Chicago’s Horween Leather Company that’s used in boots as cheap as Thorogood’s Dodgeville and as pricy as Viberg’s Service Boot. It accounts for the majority of the leather they produce.
But plenty of other tanneries use elements of both processes and that can look like vegetable tanned leather undergoing a retanning process with chrome tanning agents, or it can involve a combination of both chrome and vegetable tanning agents before it’s been dyed and finished, or (like Chromexcel) it undergoes a chrome salt “bath” before undergoing vegetable “retannage.”
So it’s hard to paint all veg-chrome tanned leather with the same brush, but while it’s tempting to say you’re getting the best of both processes it’s worth remembering that Horween doesn’t rank too highly on independent measures of environmental friendliness — chrome tanning can still be tricky in any amount.
So what’s best for your boots? Well, according to Jason Pecarich, owner of luxury heritage menswear boutique Division Road, that depends what you’re looking for.
“Chrome tannages yield flexible, supple and durable leathers which give out of the box comfort while remaining hearty for decades. Vegetable tanned leathers are more natural and full feeling and leave the grain more pronounced, patina more dramatically, and are easy to coax into shapes using heat and moisture meaning they mold a little more to the foot. Neither is better than the other, they are just different and have different qualities in wearing and how they develop.”
So whichever leather you decide to go with is ultimately up to you. Combination tanned leather is a nice compromise as far as durability and quality goes, but if it’s not an option then veg-tanned leather, though it may come with a slightly heftier price tag, will wear better and last longer. Sure, you could go for the cheap stuff, but if you want a durable boot with a beautiful look that you don’t have to feel guilty about, veg-tanned leather is the only way to go.