Vegetable tanned (or veg tanned) leather is tanned using the all-natural tannins and other chemicals found in vegetable matter such as tree bark prepared in bark mills and other such sources. It is supple and brown in color, with the exact shade depending on the mix of organic matter and the color of the skin. It is the only form of leather suitable for use in leather carving or stamping.
Vegetable-tanned leather requires a little more care and attention than leather tanned using minerals or chemical. It is not stable in water; it tends to discolor, and if left to soak and then dry it will shrink and become less supple and harder. In hot water, it will shrink drastically and partly gelatinize, becoming rigid and eventually brittle. Boiled leather is an example of this, where the leather has been hardened by being immersed in hot water, or in boiled wax or similar substances. Historically, it was occasionally used as armor after hardening, and it has also been used for book binding.
The most important organic tanning agents are the vegetable tannins present in tanning liquors. They are prepared from certain parts of plants by aqueous extraction. Their tanning power has been appreciated for a long time and Babylonian texts have recorded their use.
The use of vegetable tannins in the manufacture of leather predates recorded history, and there is creditable evidence that they were in use in Egypt as far back as 3000 B.C.
Vegetable tanning materials occur in nearly all forms of plant life. They are used commercially where the amout of tan is high and large quantities can be extracted economically. Other considerations are color and particular properties of the tan extracted. This is the conversion of a raw or green hide into leather.