What is veg-tanning?

Vegetable tanning, or veg-tanning for short, refers to the type of tannin used in the leather-making process. The two main methods of tanning are chrome-tan and veg-tan. Veg-tanning is the oldest recorded tanning method, using plant derivatives as an all-natural tannin. These tannins are commonly found in tree bark or leaves. The primary tannins used in veg-tanning are sumac, oak, quebracho, hemlock, mimosa, and chestnut. Pergamena exclusively uses a chestnut tannin for our smaller hides because of its archival qualities. However, we use a combination of chestnut and mimosa for our larger hides like cows or buffalo.

Why chestnut?

Why did we choose to use primarily chestnut for our process? While there is a very long scientific explanation for this choice, in short, chestnut tanned leather is more archival because of its durability. There are two classifications of vegetable tannins: Pyrogallol and Catechol. Chestnut and oak are pyrogallol tannins, while other tannins like quebracho and hemlock are catechol. Catechol tannins are susceptible to Red Rot. If you have ever handled old leather, especially an old book, and it starts to crumble into a reddish-brown powder, this is red rot. We decided to use Chestnut tannins to meet the archival needs of our conservators, bookbinders, and book artist clients while still providing a veg-tan leather that is as long-lasting and durable as possible for our interiors, furniture, and fashion clients.

What makes veg-tan different from chrome-tan?

There are multiple differences between veg and chrome tanned leathers. Primary among them are the environmental impact, tanning process, and inherent leather characteristics.

Chrome-tan, as the name would imply, uses chromium as its tannin. Chromium is a heavy metal and, if not treated carefully, can be very detrimental to the health of the environment and surrounding community. As of 2021, chrome-tanning accounted for about 75% of the leather production in the world. Additionally, most leather production happens in countries with minimal environmental regulations. To read more about this, check out our 2021 industry report blog post.

While there are many differences in the chrome vs. veg-tanning process, the main differences are the tannins used and the time required to complete the tanning. Chrome-tanned leather can be completed in a day, whereas veg-tan historically has taken weeks and up to months to complete. With modern technology, our veg-tanning process can be consolidated down to about two weeks.

Finally, there is a big difference in the characteristics of veg-tan and chrome-tanned leather. Both have pros and cons and are best suited for different applications.

Veg-tanned leather tends to be denser and stiffer, will patina over time, and has that beautiful leather smell we all love. Veg-tan leathers are absorbent, whereas chrome-tan leathers are not. This absorbency means that veg-tan leather will soak up the oils of your hands and patina gracefully over time. It’s this quality; however, that can also be problematic. Unfinished veg-tan leathers will stain easily, and things like rain or spills can permanently change the color of your unfished goods. (We offer both finished and unfinished leather, depending on how adventurous you might be feeling for a project.) Ultimately, veg-tan leathers tend to have more natural character, come in darker, earthy colors, and require more upkeep, but in exchange will age far more richly and wear much better than chrome-tan leathers.

Chrome-tanned leathers are lighter, softer, water resistant, and more uniform. Because of the difference in tanning processes, undyed chrome tan leather is a light blueish grey color, lighter than the cream/khaki color of our undyed veg-tan. This means chrome-tanned leather can be made in bright, vibrant colors. Due to the uniformity, lower cost, lower weight, and availability of chrome-tan, it is the leather of choice for most mass-produced leather goods.