As previously mentioned, the vast majority of leather is now chrome-tanned leather. The method itself was invented in 1858 to keep up with rising leather demand at the backend of the Industrial Revolution. Instead of natural vegetable tannins, a solution of chemicals — predominantly the acid, chromium sulphate — is used to tan the hide. The basic principle is the same (modifying the hide’s protein structure), but the process is considerably quicker and cheaper, relying more on automated machinery than manual labour.
Chrome tanned leather has its own unique set of properties. Firstly, because it can be dyed with chemical agents, chrome leather is available in a wider variety of colours than vegetable tanned leather. Thinner and softer in texture, it’s generally more resistant to heat and water — although also prone to cracking and unlikely to have the longevity of vegetable leather. Importantly, because chrome leather is not as porous as its organically produced counterpart, it will struggle to display a patina over time. And if you’re after seeking that quintessential leather smell, you will be disappointed (expect a chemically-infused scent, or very little smell at all).
One downside to vegetable tanning is that it uses a lot of water; depending on where the tannery is located, this can have a marginal or sizeable impact. Many tanneries are located by streams or rivers for this reason.
Chrome tanning, however, poses a genuine risk to eco-sustainability, particularly in developing nations with limited industrial regulation. The main threat stems from the dumping of chemical by-products — often chromium and lead — that can toxify rivers with carcinogens, kill local wildlife and render agricultural land unsuitable for farming. That said, newer methods are starting to gain traction. ‘Chrome free leather’, although still chemically tanned, makes use of chemicals that are far less harmful to the environment.