Pick up two jackets of the same cut and colour, even the same price, and you may be holding two entirely different materials. The difference is not the hide itself but what happened to it afterwards. Tanning turns perishable skin into durable leather, and today there are two principal ways to do it: with chromium salts, or with the tannins of trees. Knowing which is which tells you more about a piece than almost any label.
Vegetable tanning is the older method by thousands of years. Hides are soaked in pits or drums of tannin drawn from bark, wood and leaves (mimosa, quebracho, chestnut), and the process takes weeks, sometimes months. The result is firm, warm in colour and responsive to the world around it: it darkens in sunlight, absorbs oils from the hand, and moulds to whatever it carries. This is the leather of saddlery, belts and the wallets that look better every year. The Japanese call this deepening of colour and lustre 経年変化 (keinen henka), "change through the years", and vegetable tannage is where it shows most beautifully.
Chrome tanning arrived in the late nineteenth century and transformed the industry. Basic chromium sulphate penetrates the hide in a day or so, producing an intermediate the trade calls "wet blue" for its pale blue-grey colour. Chrome leather is soft, light, water-resistant and colour-stable, and it takes dye in almost any shade. By common industry estimates, the large majority of the world's leather is now tanned this way. It is not a lesser material: a supple lambskin jacket or a pair of dress gloves depends on exactly the qualities chrome delivers. But it ages differently. It tends to stay as it was, rather than becoming something new.
Pakistan shows both paths side by side. In Kasur, south-east of Lahore, and in the tanning clusters of Sialkot and Karachi, most production now runs through chrome drums, supplying gloves, garments and footwear to buyers around the world. Chrome made that scale possible, and it has also left real questions about effluent and water, which the better tanneries are answering with treatment plants and independent environmental audits. Alongside them, a smaller number of workshops still practise slow vegetable tanning, and those are the ones we seek out when a client wants leather that will earn its patina.
How can you tell at a glance? Look at a cut edge. Vegetable-tanned leather is usually the same tan brown right through, and its edge can be burnished smooth with water and friction. Chrome leather often shows a grey or bluish core, and its edges are usually painted rather than polished. Vegetable leather smells of wood and earth; chrome smells faintly of the workshop, or of very little at all. Many modern leathers are combinations, chrome-tanned and then retanned with vegetable extracts, which is why asking the maker is always worth it.
Neither method is right for everything. The real question is what you want the piece to become. Chrome makes a promise of consistency; vegetable tanning makes a promise of change. At LONDON COM we choose between them the way a cook chooses between a hot flame and a slow oven: deliberately, and with the finished thing already in mind.