The Chemistry of Fashion: Leather Tanning

As part of our continuing education as fashion designers, once upon a time we took a leather chemistry course.  This was, hands-down, the hardest educational course we’ve ever tackled, but at the same time it was also one of the most incredibly useful courses we’ve taken.  It was offered through the American Leather Chemists’ Association and we think some version of this should be incorporated into every fashion designer’s curriculum.

Why would we think that? Well, for starters, we learned a lot about what to look for in buying leather: how to evaluate the quality of the leather, how to determine what process was used in tanning the leather, and even how to evaluate the tanning itself.   We also learned quite a lot about the process of tanning leather from the point where the skin or hide is removed from the animal to the point where it is ready to ship as a finished commodity.

Knowing how your commodities get produced and made available for you as a designer to use in your garments is critically important from the financial point of view.  But we think it is equally important for designers to know about the materials they are using in their designs especially if they want to be able to source and use sustainable, ecologically friendly commodities.

Producing leather from raw skins has traditionally been very damaging to the environment.  For one thing, leather tanning requires huge amounts of water starting at the point where the animal parts ways with its skin to the point where it becomes ‘leather’.  The process also generates both physical waste from the biomass by-products released during tanning and from the various chemicals used to tan the leather such as chromium salts.

In the past, this physical waste (tanning salts, biomass) was released with the waste water.  Since tanneries are usually sited on waterways (easy access to enough water), this usually meant the waste water was just dumped into the water source below the tannery.  Pity anyone who lived downstream of the tannery! Not only does the rotting biomass (removed during the early part of tanning) stink as it degrades, but as the biomass is degraded by microbes, excess carbon dioxide is released into the waterways, disturbing the natural balance and causing things like algal blooms and fish die-off.  If that weren’t bad enough, though, the tanning chemicals (like sulfuric acid and chromium salts) are released along with the waste water.  These chemicals are quite toxic and have been linked with everything from birth defects to cancer.

Thankfully, leather chemists and organizations like the ALCA are working to find new ways of tanning leather that don’t use as many toxic chemicals and that enable better retention and capture of the waste chemicals.  Leather tanning today is a much safer process than it was even twenty years ago, and as new technologies and processes emerge, we expect that the tanning process will become even safer.

As designers, we need to understand how our design choices will have an impact, not only on the purchasing consumer, but also on the environment in which our consumer lives.   It is therefore critically important that we learn as much as we can about the commodities we select to develop our designs in.  It is no longer enough to create simply pretty or dramatic fashion.  We also need to design intelligently and thoughtfully, with full awareness of what we are selecting, and the impact those selections have.