About Vegetable Tanning
The leather tanning process dates back all the way to 6000 B.C.—humans needed durable, protective clothing and housing, and turned to animal hides to meet these needs. However, hides by themselves would not last the test of weather or time, so they discovered various ways to tan the hides in order to strengthen and preserve them. Historians have found four different ancient leather tanning methods: alum tanning, oil tanning, brain tanning, and vegetable tanning.
The only ancient method still in existence today in the modern era is vegetable tanning, which is the process of using tannins or naturally-occurring plant polyphenols to preserve, strengthen, and color leather.
Tannins, or tantric acids, are pale-yellow to light-brown organic substances in bark, wood, roots, leaves, and fruits of plants. The tantric acids from oak trees, chestnut trees, and mimosa trees are widely used for vegetable tanning, but there are hundreds of other plants that could be utilized to derive tannins. (Fun fact: in addition to tanning leather, tannins can also be used to make ink or natural dyes, to clarify wine and beer, and are even to treat certain medical conditions.)
The various sources for tannins create different colors—tannins from chestnut wood and sumac leaves give a light creamy shade while tannins from mimosa bark and quebracho wood give a pinkish to rich reddish tan.
The traditional process of vegetable tanning leather with these tannins is fairly time consuming—it requires soaking these leather hides in the tannins for months.
Today, vegetable tanned leather is only 10% of the leather market, as global production has shifted to the cheaper, quicker, (but controversial and environmentally hazardous) process of chrome tanning.
There is, however, still a market for vegetable tanned leather, as this natural form of tanning is better for the environment and results in a high quality, textured, unique leather. Veg-tanned leather also has a distinct and authentic character with its variances in colors and a natural, woody, earthy smell. Plus, veg-tanned leather is biodegradable. Vegetable tanning also creates a sturdier leather, which makes it especially useful for shoes and upholstery.
And what many love about the appearance of veg-tanned leather is that it develops a patina—the naturally occuring brown color that forms on objects over time, which can increase the value and aesthetic appeal.
Historically, cold water was used to extract tannins from plants, but today boiling water is used to more quickly extract the tannins. The tannins are then sold to tanneries in either powder or liquid form. Tannins in powder form have twice the level of concentration as the liquid form, so powders are generally preferred.
Photo Credit: Wickett & Craig
In order to prepare the hides for tanning, hair and wool must be removed and the hides are rehydrated.
Once the hides are prepped and ready to be tanned, they are put into large pits, or vats, to soak into concentrations of tannic acids for weeks.
Tanneries could have dozens of pits (U.S. vegetable tannery, Wickett & Craig uses 72) that each have different levels of tannin concentration. Typically, the pits at the top have the strongest concentrations, and the pits at the bottom have the lowest concentrations. The vegetable tanning begins with placing the hides in the pits at the bottom with the weakest level of tannin concentration and then are moved progressively upwards to pits with higher concentrations.
Photo Credit: Wickett & Craig
The process of tanning the skin typically takes weeks and the pits must be tended to (i.e. replenished and recirculated) to ensure maximum tannin absorption.
After the hides have soaked in the pits for a few weeks, some tanneries take the hides out and lay them flat, layering the hides on top of each other with layers of bark placed in between.
Once the tannins are set in, excess moisture is removed and the leather may be split and shaved to achieve the desired thickness.
After this, the tannery will apply their own unique blend of conditioning oils and waxes to smooth out the leather and increase the color concentration and durability of the leather. Then, the leather is fully dried out. The tanneries will stretch out the leather and clamp it to ensure there are no wrinkles, and then the hides are air-dried in a temperature-controlled space.
Photo Credit: Wickett & Craig
To finish off the process, tanneries will give one final conditioning treatment and may even iron the leather to smooth it further before sending out their completed vegetable tanned leather.
Brands Using Vegetable-Tanned Leather
When Woolly founders, Jake Fromer and Jeff Heil started out four years ago in the basement of their Portland rental, they were making wallets with felted wool (hence, the name, Woolly). They soon realized, though, wool gets worse over time. And when putting a product like a wallet out there in the world that’s meant to be used every day for years, durability is key.
From Jake and Jeff's backgrounds in design and materials innovation, they knew about vegetable tanned leather and all of its advantages. Not only is the veg-tanning process much better for the environment than chrome tanning, but it produces a more authentic leather material that lasts longer and darkens beautifully over time. This “patina” effect is quite incredible—the leather actually gets better the more you use it—and no two wallets end up looking the same. There are few materials that work this way, so Woolly is proud to use one of them in their products. So proud, in fact, that they often must fend people off who come up to them at craft fairs wanting to buy their year-old, worn-in example wallets instead of the brand new ones. “Sorry, that one’s not for sale!” they'll say.
In many ways, Woolly is breaking from tradition in the handmade leather goods industry. The brand uses technology and a fresh perspective to make products that move past the traditional aesthetic and production techniques of their peers for a more modern look and feel. But Woolly does it without forgetting the importance of using quality materials, ethical sourcing and making products that last—some of the values Woolly shares with a rising generation of more conscious consumers.
Woolly proudly sources their leather from Wickett and Craig, one of the few remaining vegetable tanneries in the US. In their own small way, Woolly is helping to carry forward this ancient and important tradition, which has been used to create beautiful leather goods for thousands of years.
Woolly's collection on Made Trade includes: wallets, keychains, luggage tags, and apple watch bands
Woolly Products We Love:
Zemper exclusively uses the highest grade vegetable tanned leather and materials they can find. This leather is crafted through the world's oldest and most labor intensive tanning process, vegetable tanning. The process of vegetable tannin utilizes environmentally safe, natural tannins found in a select few plants throughout the world. As opposed to the far more common chrome tanning process, which uses harsh chemicals to tan hides in as quickly as 24 hours, vegetable tanning can take up to 6 weeks to produce a single batch of skins. Zemper has chosen to not use chrome tanning because of it's toxic chemicals that break down the binding collagen in skins, and often find their way into local water systems through illegal dumping. The trade off of ethics for efficiency is common, but Zemper is committed to the traditional, natural, thoughtful process of vegetable tanning.
Only a small handful of tanneries still practice vegetable tanning, and yet it is used by the best leather workers in the market for its tendency to develop a rich patina with use, its durability of form, and durability that makes it last lifetimes. Everything made at Zemper is sourced ethically and with sustainability in mind. Zemper sources their vegetable tanned leather from two tanneries: Wickett and Craig in Pennsylvania in the U.S. and from Conceria walpier in Tuscany, Italy. Zemper also uses 100% linen thread and solid copper and brass hardware. Zemper's veg-tanned pieces are all cut and hand-stitched in Portland, Oregon.
For the team at Zemper, their balanced designs and hopes to create something that will outlast them run hand in hand with their devotion to passing on a healthy world for future generations. The team at Zemper firmly believes that if they can leave something beautiful behind in this world, then they have done their job.
Zemper's collection on Made Trade includes: tote bags, wallets, and belts
Zemper Products We Love: