Tradition and implications: chromium and chrome-tanned leather

Ever since the world has started turning to sustainability and eco-friendliness, chromium has been in the spotlight. Chrome-free leather (also known as FOC) is being advertised as better, smarter and more sustainable of its counterpart, but are we sure that chromium is the real opponent to fight against?

In this article we look into the matter trying to better understand chromium and chromium-related concerns.

 

In the history of leather processing, tanning has not gone through major transformations. Until the 19th century, vegetable tanning was the most popular technique – alum and other methods were occasionally used, but they were not even close to the prevalent one. Things changed in 1858, when two European technologists (Friedrich Knapp from Germany and Hylten Cavalin from Sweden) invented chrome tanning, which was later patented by the American chemist Augustus Schultz.

The innovation immediately took hold: the new process was significantly faster than the old, vegetable-based one – that is why chrome tanning quickly became the most common leather processing technique. The coeval discovery of fatliquoring (also known as “regreasing”) along with the development of synthetic dyes took care of the rest, confirming chrome tanning as the most popular method. The leather resulting from this kind of processing took the name “wet blue”, with reference to the characteristic hue of the chrome-tanned hides.

 

Before we dive into further considerations, an essential distinction should be made between chromium (III) and chromium (VI). While the first is harmless as well as an important nutrient that the human body needs in order to process certain sugars, proteins, and fats, the second is a carcinogenic substance that can cause ulceration and fatal poisoning.

Chromium (VI) is definitely harmful, but it generally occurs when leather is processed under improper tanning conditions, or when chrome-tanned materials are disposed of without appropriate handling or kept under high heat conditions without being regularly reviewed.

Today, chromium (III) salts are employed in around 85% of global leather production (as per 2014). Almost all leather shoes and clothing are produced using chrome-tanned material, while FOCs are gaining ground in the upholstering sector. The differences between chrome-tanned and vegetable-tanned leather are many: chrome-tanned leather is stronger, lighter, and softer, and it can be waterproofed more easily.

 

Unfortunately, the justified concerns about chromium (VI) have led to a general suspicion towards chrome-tanned leather, and producers are likely to pay the price. Advertising FOC products by the words “produced without chromium and pollutants” is devious, because it equates both kinds of chromium (III and VI) and associates chrome tanning with unhealthy practices. The media covering transgressions involving chromium (VI) may have caused some confusion as well, giving the impression that chromium is harmful per se.

 

Today, chromium tanning still dominates the market. Alternative tanning methods are spreading, but at the moment none of them seems able to replace it completely.