Leather

Tanning is one of the oldest crafts practiced by humans; vegetable-tanned leather footwear dating to roughly 5,500 years ago, found in the Areni-1 cave in Armenia, is among the oldest leather artifacts ever recovered, and vegetable tanning remained essentially the only method used for millennia. Vegetable tanning uses tannins extracted from tree bark, leaves and other plant matter and typically takes weeks, producing a firm leather that is prized for belts, saddlery and leathercraft.

Chrome tanning is a 19th-century development. After chromium (III) solutions began being used in the 1840s to preserve medical sutures, tanners adapted the same chemistry to hides, and chrome tanning emerged as a commercial process later in the 1800s. It can tan a hide in under a day rather than weeks, producing a softer, more stretchable leather suited to handbags and garments, and today accounts for the large majority of leather produced worldwide.

Not all material sold as "leather" is the same. Full-grain leather retains the complete grain layer of the hide with nothing sanded, buffed, or removed from its surface, keeping the tight, natural fiber structure intact; this is why it is generally regarded as the strongest and longest-lasting grade, and why it develops a patina rather than simply wearing out. Top-grain leather also comes from the outer hide but has had the top layer sanded and often refinished, making it thinner and more uniform, though somewhat less durable over time.

Further down the quality scale, split leather is cut from the lower layers of the hide left after the top grain is removed, and is used for suede or coated to imitate higher grades. "Genuine leather" is not a formal grade at all but a marketing term that is often applied to this lower-tier material. Bonded leather sits at the bottom, made from scraps and fibers of leather bonded together with polyurethane or latex, sometimes containing only a small fraction of actual leather content.