Leather Origins and Making
What Is Leather Made Of? Collagen, Tanning Agents and Finishes
Leather is mostly collagen from animal skin, locked by a tanning agent and finished with oils, dyes and coatings. See each component and what it does.
Leather is made mostly of collagen, the protein fiber network in an animal's skin. A tanning agent stabilizes that collagen so it no longer rots. The tannery then adds oils, dyes and often a surface coating.
This page is part of our guide to where leather comes from and how it is made.
What is in a piece of leather
| Component | What it does | Fact |
|---|---|---|
| Collagen fibers | The structure itself; about 70% of the skin's dermis | – |
| Tanning agent | Locks the collagen so it resists heat, chemicals and microbes | – |
| Fats, oils and waxes | Fixed to the fibers in fatliquoring to keep leather supple | – |
| Dyes | Give the color during crusting | – |
| Fillers | Dense chemicals that make some leathers harder and heavier | – |
| Finish coating | Sprayed, rolled, polished or embossed on some leathers | – |
| Water | Leather is dried to set levels, commonly 14% to 25% | – |
Which part of the skin it is
Leather comes from the dermis, the layer under the thin epidermis. Its top, the grain, has thin, loose bundles of mainly type III collagen. The deeper reticular layer, or corium, has thick type I bundles that give leather its tensile strength.
That split matters on labels. Top-grain leather keeps the grain, while split leather is the corium left after the top is cut away. Suede is made from the napped underside of the skin; see where suede comes from. For the makeup of a fresh raw hide by weight, see hides and skins in leathermaking.
What is taken out first
Tanners strip away most of what is not collagen. Liming removes unwanted proteins, unhairing takes off hair, fleshing removes the layer under the skin, and degreasing removes natural fats. Bating enzymes remove proteins such as elastin and albumin but must not damage the collagen.
The tanning agents compared
Chrome tanning was invented in 1858 and by the 20th century made about 85% of all leather.
Reactions, the American Chemical Society's video series, explains how tanning stabilizes collagen with plant polyphenols or chromium(III), and what fatliquoring adds. It gives about 90% for chrome-tanned leather today, a little higher than the 85% figure above.
| Agent | Result | Fact |
|---|---|---|
| Chromium salts | "Wet blue"; about a day; the most common method | – |
| Vegetable tannins (tree bark) | The oldest known method | – |
| Aldehydes | "Wet white"; the main chrome-free type | – |
| Alum (tawing) | Not a true tan; reverts to rawhide if soaked long enough | – |
Made of leather, or made to look like it
Bonded leather is shredded leather scraps glued with polyurethane or latex onto a fiber mesh, with 10% to 90% leather fiber. Faux leather has no collagen at all: it is plastic, such as PVC or polyurethane, on a fabric base. For the full list of materials sold as "leather," see what leather is made from.
Riding gear from Leather Collection is made from cowhide leather, with kangaroo as an option on some suits.
FAQ
What is the main ingredient of leather?
Collagen, the main structural protein of skin. Tanning stabilizes it so the material stays flexible and does not rot.
Are leather cows used for meat?
Cowhide is a product of the food industry, taken from cattle raised for meat. See where leather comes from.
HitKB Editorial Team
HitKB articles are researched from published sources, cited in the text, and reviewed before publication.