5 October 2021
Leather-making is a science rooted in craftsmanship. Despite its artisan image, there’s a good case for arguing that leather-making is simply applied chemistry. Especially today, when tanners and chemical specialists invest vast amounts of time and money in researching, improving and perfecting the chemistry of leather making.
Originally, leather tanning occurred naturally or was done by man using natural resources in a process that was the precursor of today’s ‘vegetable tanning’. But leather production has always looked for more efficiency and better performance. Since 1840, chemistry has taken over the role of tanning agent from traditional tannins, alum and oils. In old footage and reports, you’ll often find stories about the downsides of chemicals, but today, this is a very different story.
Chemicals and leather production
Much of the contemporary research by chemistry suppliers and tanners focuses on minimizing the impact of chemicals on human health and the ecology. Over the last three decades, safe chemical management and sustainability have become the hallmarks of a responsible tannery with high-quality products.
For chemistry management within leather production, one of the major challenges is the diversity of methods. The process steps may be broadly the same, but each type of leather application and industry require different technologies. Chemicals, either aqueous or spray, are used to clean the hide, modify its structure and add the desirable characteristics to the final leather. The craft side of the industry further complicates things, as each tannery follow its own distinct processes and recipe. An automotive tanner will not use the same methods for its leather as a shoe-leather tanner or automotive competitor. This makes perfect sense, as each tanner relies on their signature look and feel for their product.
There are three main tanning systems in use today, namely:
• Wet blue tanning (chromium-based)
• Wet white tanning (alternative tanning solutions)
• Vegetable tanning (tanning based on plant-based technologies).
Industrial tanning methods have, for a long time used Chromium (III), which is a highly effective tanning agent (chrome tanning often takes less than a day). It’s use is tightly controlled to avoid and eliminate any formation of Chromium (VI). Chromium (III) is a non-toxic material that is found in many everyday items such as stainless steel cutlery. Aldehydes, aluminum or other compounds are used in wet white tanning, which yields softer leather. In recent years, a big switch to biotechnology, using natural oils and other food by-products as resources, has emerged to enable more circular processes.
Salt and water……to read the rest of this article from One 4 Leather, click on One 4 Leather – Chemistry and Sustainable Automotive Leather