Vegetable tanned leather refers to the tannage, or method of tanning the cowhide into leather. It’s called “vegetable” because of the natural tannins used in the tanning process like tree bark. Vegetable tanning or veg tan as it’s sometimes called, is one of the oldest methods of tanning known to man. It has literally been around for centuries. But less than 10% of the world's leather is tanned this way today.
What makes vegetable tanning so unique is it can be used to make thicker leather and results in more body and character - perfect for bag making. Vegetable tanned leather also tends to age better and develops a rich patina over time. And it has that awesome classic leather smell.
Here's a great video from Wickett & Craig that provides an overview of the process:
First, the hides have to be prepped. So they spend a couple days rehydrating the hides and removing the hair. The whole hide is cut into two pieces called sides.
The split hides are then put into large vats filled with natural tannins. Some of these natural tannins include tree bark. The hides spend a couple of weeks soaking in this tanning liquor and must be frequently tended to in order to ensure full absorption. The hides are then removed, excess moisture is taken out and they are shaved to the desired thickness (from the backside).
For vegetable tanned leather that isn’t dyed, this is nearing the end of the road. That type of veg tan leather has a pale almost pinkish color to it. But dyed veg tan leather is further dyed to create the rich color and character that makes the leather so unique.
The tanned hides arrive at this step as a blank canvas and ready to be infused with rich color and character. The hides are dyed in enormous drums that look something like a wine barrel on steroids that rotates in the air.
The leather may then be hot stuffed, which is a special process that literally stuffs the leather hide to its core with waxes and tallows that give it a rich color and make it more durable.
After that, the hides are dried and staked. Staking is a process that softens up the leather just a bit.
In this stage, the hides are sprayed another time with waxes and a sealant for protection.
The entire process is very time and labor intensive, taking up to six weeks to complete.