Leather Tanning Process

We’ve been working together with the Sheong Shi Tannery in Kolkata since 2010 to improve, expand and promote the production and use of eco-friendly leathers. We have noticed that the interest in sustainable leather tanning processes has increased in the last years. This is great news, because it means that the industry is becoming more concerned with their environmental impact. Curious how our leather is made?

Wet White Tanning

The Sheong Shi Tannery uses a process called ‘wet white tanning’ for all their eco-leathers. This method of tanning is a safer, more environmentally friendly process free of harmful chemicals, like chromium, heavy metals, formaldehyde, short-chain chlorinated paraffin, volatile organic compounds or alkyl phenol ethoxylates. To verify this, the leather is tested by SGS, an independent inspection agency.

The tanning process of eco-leathers is comprised of a combination of synthetic tanning agents and natural vegetable extracts. It’s so clean that leftover leather can be recycled and used as fertilizer, unlike chromium-tanned leather. The name of this tanning process derives from the fact that, after the process, hides look white instead of blue like the chrome-hides do.

As the eco-friendly leathers aren’t treated with heavy chemicals, they can only be preserved for 6 weeks, so it can’t be held in stock by Patrick, compared to his other leathers. This is one of the reasons why the production is more difficult to manage and also why the production-time of our bags is so long, the process of just tanning the leather can take up to 8 weeks!

The Tanning Stages

After the preparatory stages when the hide is prepared for tanning by removing many of the unwanted raw skin components, the hide is ready for the tanning. Tanning is the process that converts the protein of the skin into a stable material that will not decompose and is suitable for a wide variety of end products, such as leather bags and accessories. The hides are loaded into a drum and immersed in the tanning liquor. They soak while the drum slowly rotates and the tanning liquor slowly infiltrates the full hide. Regular checks by the workers are necessary to see if the penetration is even.

After the tanning, the skin goes into the crusting phase when the hide is thinned (which is called shaving), re-tanned and lubricated. Most importantly, in this phase, the skins are dried, softened and receive their color.

The last phase of the tanning process is the finishing, where surface coating is applied. Our eco-friendly leathers hardly have any finishing, this leaves them very open to change during use and gives them their vintage look over time. It incorporates the fat on our skins and the shine because of rubbing against our clothes.