TL;DR Vegetable tanning is a natural form of tanning leather that dates back thousands of years. The process of vegetable tanning is slow and methodical and is much safer for people and the environment than conventional chrome tanning.
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 harsh 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 occurring 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.
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.
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.
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 on Made Trade Using Vegetable-Tanned Leather
Dedicated to quality, versatility, and sustainable standards, Nisolo creates excellent sustainable shoes and accessories using vegetable-tanned leather. They responsibly source their leather from tanneries committed not only to the ethical treatment of animals but also to using earth-friendly systems of waste disposal. Nisolo’s artisan makers all receive healthcare, beyond fair wages, and work in safe and healthy working conditions.
Purse & Clutch employs artisan seamstresses, leatherworkers, and weavers in Guatemala, Ethiopia, and Mexico to craft their handbags and accessories. The artisans all receive a living wage, work in healthy working conditions, and craft their products in slow, small batches.
Abby Alley creates handcrafted jewelry and versatile bags using locally sourced materials. Globally-minded and committed to providing economic opportunities, Abby Alley employs women artisans in Kenya and Tanzania who receive fair wages and work in safe and healthy environments. The artisans’ expert craftsmanship ensures unrivaled quality and durability, ensuring their pieces can withstand the wear and tear of everyday life for years.