There are many ways to tan leather, but the most widely used are chrome-tanned and vegetable-tanned leather. The difference between chrome and vegetable tanning is the way the moisture is extracted from the raw hides. In chrome tanning this is done using chemical compounds (chromium based) while a vegetable-tanning process uses only natural ingredients.
“The difference between chrome and vegetable tanning is the way the moisture is extracted from the raw hides”
The majority of the leather produced is chrome-tanned (80-90%), but the finest leather goods are made with vegetable-tanned leather. Vegetable-tanned leather is preferred for leather goods because it’s perceived to be better for the environment, it’s highly durable and it has the ability to develop a beautiful patina.
There are two simple tests you can try to determine whether the leather is chrome, or vegetable-tanned. Usually a chrome-tanned leather looks more synthetic, smells less organic and feels more flimsy compared to vegetable-tanned leather, but sometimes telling them apart can be tricky.
“There are two simple tests you can try to determine whether the leather is chrome, or vegetable-tanned”
Test 1: Put a small narrow strip of leather in boiling water. If the leather instantly curls up, it is vegetable-tanned. A chrome-tanned leather will just float around in water.
Test 2: Burn a piece of leather with a lighter. If you have a vegetable-tanned leather, it will not burn in flames and the ashes will be grey or black. A chrome-tanned leather will burn more easily and its ashes are green.
When a hide arrives at the tannery it is around 2cm thick. This is split into several layers which are sold as different types of leather. It is the outmost layer, just below the hair, that we are after and this is called the full grain. Full grain leather is the strongest, most durable leather and the only part that will develop a beautiful patina over time.
“To identify full grain leather you need to look closely at the surface for ‘the grain’”
To identify full grain leather you need to look closely at the surface for ‘the grain’ (pores) of the leather, this is where the hair once grew. A magnifying glass could help at this stage. If you see these small pores looking like small craters, then you have found a full grain leather.
If the surface is completely smooth and lacks a natural structure, you have what is called a corrected grain or a lower layer split. On a corrected grain the top layer (a couple of mm) has been removed by sanding and buffing to remove imperfections. The corrected grain is often used for cheaper leather goods and is nowhere near the full grain leather in terms of durability.
source : https://www.carryology.com/