Leather is made in five stages: curing the raw hide, prepping and de-hairing it, tanning, re-tanning and dyeing, then finishing. Curing salts the raw hide so it stops rotting on the way to the tannery. Prep soaks it soft and strips the hair. Tanning is the step that turns a hide that would rot into leather that will not. Re-tanning and dyeing set the firmness and the color. Finishing dries it, softens it, and seals the surface.
The one stage that decides almost everything about the finished leather is tanning, and there are two ways to do it. Veg-tan takes months and uses bark. Chrome-tan takes a day and uses salts. That is why one patinas and the other does not.
Stage 1: Curing the raw hide
A raw hide starts to rot within hours of coming off the animal, so the first thing a tannery receives is a hide that has been cured. Curing packs the hide in salt, by brine or dry salt, which pulls the water out and stalls the bacteria that break it down. A cured hide keeps for weeks and ships without spoiling. Nothing about the leather is decided yet; curing only buys time to get the hide to the next stage intact.
Stage 2: Prepping and de-hairing
This stage is wet, and it happens in the part of the tannery called the beamhouse. The hide is soaked to rehydrate it, then run through lime, which swells the hide open and loosens the hair at the root. A machine scrapes the hair off the grain side and the fat and flesh off the underside, the flesh side, the rougher back of the hide. What is left is a clean, swollen, colorless hide ready to take a tan. Chrome leather gets two extra steps here: bating, an enzyme bath that relaxes the swollen hide back down, and pickling, an acid-and-salt soak that preps the fibers to bond with chromium.
Stage 3: Tanning
Tanning is the step that makes leather leather. A clean hide is still raw collagen, and raw collagen rots. Tanning works a chemical into the fibers that locks them so they will not putrefy, stiffen into rawhide, or break down. There are two common methods, and they produce different materials.
Vegetable tanning uses tannins drawn from tree bark and wood, oak, chestnut, quebracho, and mimosa among them. The hides soak in progressively stronger tannin liquors, and the process is slow: weeks in drums, and historically months in pits. Veg-tan comes out firm and dense. It holds a tooled stamp, it can be wet-molded to a shape, and it darkens with use into a patina, the deeper color and sheen leather earns from oil, light, and handling. Belts, holsters, saddlery, and strops are veg-tanned for that firmness.
Chrome tanning uses chromium salts, basic chromium sulfate, worked into the hide in a rotating drum. It is fast: a hide can go from pickled to tanned in about a day, coming off the drum as a pale blue-grey sheet the trade calls wet blue. Chrome leather is soft, flexible, water-resistant, and holds dye in bright even color. It does not firm up or take a tooled stamp the way veg-tan does, and it does not patina the same way. Most leather made today is chrome-tanned, because it is faster and cheaper and the result is supple straight off the drum.
The short version: veg-tan takes months and uses bark, chrome-tan takes a day and uses salts, and that is why one patinas and the other does not.
Stage 4: Re-tanning, splitting, and dyeing
A tanned hide is leather, but it is not finished leather. Three things happen before it looks like the material in a wallet or a belt.
Splitting and shaving. A thick hide is split into layers through its thickness. The top layer carries the grain, the dense outer surface where the fibers are tightest; the lower layer is the split, the looser flesh-side leather that becomes suede or a backing. Then a shaving machine evens the leather to a target thickness, measured in ounces, where one ounce is about one sixty-fourth of an inch, so a 9-ounce belt leather is about an eighth of an inch thick.
Re-tanning. A second, lighter tanning step tunes the temper, how firm or soft the leather is, and fills it out so it cuts and finishes evenly. This is where a tannery dials a hide toward stiff strap leather or soft garment leather.
Dyeing and fatliquoring. The leather is dyed, either drummed through so the color runs all the way into the leather, or sprayed on the surface. Then it is fatliquored: oils are driven into the fibers so that when the leather dries it stays soft and bends instead of cracking. Skip the oil and the leather dries board-stiff.
Stage 5: Finishing
Finishing dries the leather and sets the surface. The wet leather is dried under vacuum or hung on frames, then softened by staking, a flexing that breaks the stiffness out of the fibers. From there the finish depends on the grade. A full-grain, aniline finish gets little more than a light topcoat, so the natural grain and the marks from the animal's life stay visible. A heavier pigmented finish sprays color and a sealing coat over the surface, which evens the look and hides marks but buries the grain. Buffing, embossing, and glazing happen here too. When the finish is set, the hide is graded, measured, and shipped.
Vegetable vs chrome tanning, side by side
| Vegetable-tanned | Chrome-tanned | |
|---|---|---|
| Tanning agent | Tannins from tree bark and wood | Chromium salts (chromium sulfate) |
| Time | Weeks in drums, historically months in pits | About a day |
| Temper | Firm and dense | Soft and supple |
| How it ages | Darkens into a patina | Holds its color; does not patina the same way |
| Takes tooling/molding | Yes | No |
| Typical use | Belts, holsters, saddlery, strops | Garments, upholstery, soft bags, footwear |
A note on leather grades
How leather is made is a separate question from what grade you end up with. Full-grain, top-grain, genuine, and bonded describe how much of the hide's grain survives into the finished piece, not how it was tanned. For that, see full-grain vs genuine leather.
Ezra Arthur makes its wallets, belts, and bags from full-grain leather. Shop our leather goods.