How Leather Is Produced: The Chain from Hide to Finished Leather

Leather is produced by taking the hide or skin of an animal, curing it so it doesn't rot, and processing it in a tannery: cleaning and unhairing, tanning with chromium salts or plant tannins, then dyeing, oiling, drying and finishing. In a UNIDO model, one tonne of salted cattle hides yields about 255 kg (about 560 lb) of finished leather. Most leather comes from cattle, at about 65% of all leather produced.

This page is part of our guide to leather tanning and production. It follows the whole production chain, with numbers for what goes in and what comes out. For each tannery operation in detail, see how leather is made: from raw hide to finished material.

The production chain at a glance

Where the hides come from

Almost all of the world's leather is made from the hides of animals raised for meat. By share of leather produced, cattle make up about 65%, sheep about 13%, goats about 11% and pigs about 10%.

Whether leather is only a by-product is disputed. The FAO describes hides as mainly a by-product of the meat industry, so hide supply barely responds to demand for leather.

Veganuary argues that leather is a profitable trade in its own right. For the ethics, see is leather ethical?.

Curing: keeping the hide from rotting

Left untreated, bacteria would spoil the hide's collagen, so it is cured first. Salt draws out water so bacteria cannot grow. Wet-salted hides are packed in salt for about 30 days, and brine-curing takes about 16 hours.

Salt has a cost later. Soaking salted hides in the tannery produces 7-9 m³ of salty effluent per tonne, and normal treatment doesn't remove the salt. Chilled, unsalted hides cut the chloride load from about 85-113 kg to 5-10 kg per tonne.

Inside the tannery: four stages

UNIDO groups tannery work into beamhouse, tanning, post-tanning and finishing.

1. Beamhouse. Hides soak, then lime and sodium sulphide loosen the hair. Ammonium salts and enzymes delime and bate them, and a pickle readies them for tanning. This removes the hair and the flesh layer, leaving the collagen-rich corium.
2. Tanning. In chrome tanning, chromium(III) salts bond to the collagen and the hide turns greyish-blue ("wet blue"). In vegetable tanning, plant tannins do the same job more slowly: two weeks in tannin vats at one US tannery. About 85-90% of leather is chrome tanned.
3. Post-tanning. The hide is split and shaved to thickness, then retanned, dyed and fat-liquored with oils and waxes.
4. Finishing. The surface is sprayed, coated or waxed, pressed or ironed. Each hide is graded and machine-measured, because leather is sold by area.

Splitting can happen before tanning (after liming) or after it, in the blue. Most tanners prefer splitting after liming because it means less chrome-containing waste.

What goes in and what comes out

UNIDO's mass balance follows one tonne of wet-salted cattle hides (39 hides) through a model chrome tannery making shoe-upper leather.

The model dates from 2000, and UNIDO notes that real tanneries can differ considerably. Even so, the point stands: most of what enters a tannery leaves as something other than leather.

Waste, water and chemicals

• Liming effluent is the most polluted stream in the tannery, at 9-15 m³ per tonne of hide, according to a UNIDO pollution-load study.
• Chromium. Chromium(III) is much less toxic than chromium(VI), but poor waste treatment can turn one into the other. One peer-reviewed study found about 40% of the chromium used in industrial tanneries ends up in wastewater.
• Smell and gas. Hydrogen sulphide and ammonia are released during deliming, and rotting fleshings add odor.
• Solid waste. Hair, flesh, trimmings and shavings make up much of the material that doesn't become leather. UNIDO says cleaner processes can turn some of it into by-products.

Audits such as the Leather Working Group standard check tanneries on effluent, restricted substances, chromium VI and traceability. For the wider picture, see how environmentally friendly is leather?.

Where leather is produced

Italy accounts for about 67% of the value of European leather production and about 25% of the global value. Pakistan's trade authority counts about 800 tanneries and puts the country's share of global leather production at 0.9%.

Its processing is concentrated in Sialkot, Kasur and Karachi. See leather from Pakistan and Italian leather.

From finished leather to a product

The finished leather goes to makers, who buy it by area and then cut it into panels. How much of a hide ends up in the product depends on its grade and marks. Clean upper leather cuts at about 75-85% yield, and a lower selection with more natural marks at 60-70%.

Made-to-order jackets from Leather Collection are made and shipped from the company's facility in Pakistan. Each product page names the animal, but the category pages do not state the tanning method.

Related pages

• What is a tannery?: the plant itself, its types, chemicals and smell.
• How suede is made: what happens to many split layers.
• Vegetable-tanned leather hides: what to know: buying hides from veg tanneries.

FAQ

Is leather from horses or cows?

Mostly cows: cattle hides make up about 65% of leather. Horsehide is used for some very durable leathers, including shell cordovan.

Is real leather waterproof?

That depends on the tannage and finish. Vegetable-tanned leather discolors in water, and if soaked then dried it shrinks and hardens. Chrome-tanned leather holds its color and shape better.

Can you recycle leather?

Leather scraps and fibers are shredded and bonded onto a backing to make bonded leather. In US trade rules, bonded leather must not be sold as plain "leather". Tannery solid wastes can also become by-products.

Do cows need to be killed for leather?

Leather comes from hides of animals raised for meat or hunted. Whether the hide is a by-product or a driver of the trade is disputed.