Why Tanners Once Used Urine and Dung: Tanning Before Chemistry

Old tanners used urine to loosen hair and dung to soften hides. In the sources we read, both belong to the preparation of the hide, before the tanning itself. The dung worked because bacteria in it make enzymes that act on the skin, and modern tanneries use purified enzymes instead.

This page is part of our guide to leather tanning and production. It explains what each step did and what replaced it. It is history, not a how-to.

The old steps and what replaced them

Urine: loosening the hair

Before a hide can be tanned, the hair has to come off. The SATRA Bulletin, from a footwear and leather technology body, says skins were soaked in urine, or left to putrefy for several months, so the hair loosened. A medieval historian writing in 2026 says that tanners soaked or sprinkled hides with urine, lime or ashes to speed this up.

Urine had to be collected. The SATRA article says urine pots stood on street corners for tanneries and laundries.

Why urine worked is less well documented. One general history site says urine contains urea, which breaks down into ammonia, and that ammonia breaks down organic matter. That site cites no sources, so treat it as an explanation, not a finding.

Lime was the other hair remover, and its timings varied. An Italian guidebook gives fifteen days in lime, while Venice's 1401 statutes call for one or two days, then a week back in lime.

Dung: what bating and puering did

After dehairing, tanners softened the skin in a bath of dung, partly to clear away excess lime. [Wikipedia's article on bating](https://en.wikipedia.org/wiki/Bating_(leather)) describes bating with hen or pigeon manure, soaked for a few days, and puering with dog dung.

The dung did the work through bacteria. They produce enzymes, and Wikipedia says aged dog feces was more potent than fresh because bacteria on it release the enzyme trypsin. SATRA adds that tanners often kneaded skins in the dung barefoot for two or three hours.

Another medieval account describes the same step with a warm infusion of bird guano or animal dung to remove excess lime, or fermenting barley with stale beer or urine. That historian does not use the word "bating" for it.

Not every tradition did this. Wikipedia reports that puering and bating were not used in all early methods, and that tanners in 12th-century Egypt and in Yemen used acacia tannins instead.

Why tanneries sat outside town

Tanning was an "odoriferous trade", and tanneries were pushed to the edge of town. Bristol banned tanners from working within its walls in 1344, and a London inquiry in 1355 found tanners' waste, including the excrement they used, dumped near the Fleet prison.

Tannery smell today has other causes: putrefying hides and trimmings, hydrogen sulphide, ammonia and volatile organic compounds. For the modern plant, see what a tannery is.

What replaced dung

Puering with dog dung fell into disuse after pancreatin, an enzyme preparation, became available on an industrial scale in 1895-1897. Today the enzymes are purified, and the process no longer needs bacterial fermentation. Conventional bating uses ammonium salts together with proteolytic enzymes.

Wikipedia calls bating the one step where enzymes cannot be replaced by chemical processes. Chemistry took over elsewhere, such as the lime and sodium sulphide used for unhairing. Our guide to how leather is produced follows the whole chain.

Where dung is still used

SATRA says Fez tanneries still use pigeon dung.

National Geographic's 2013 film shows a worker in a Fez tannery kneading skins in a vat of pigeon droppings and water for almost three hours. A worker there says the droppings "bite" into the skin; the sources above credit bacterial enzymes, so read that as a worker's description, not a chemical explanation.

Where this leaves a leather buyer

Nothing in these old methods tells you how a modern jacket was made. Leather Collection's product pages do not state a tanning method, so we cannot say how any piece was prepared. For a look at the craft region behind much leatherwork, see Leather Collection's page on Sialkot craftsmanship.

To see how these steps fit into tanning as a whole, read what it means to tan leather. For hands-on methods, see how to tan hides into leather and how to brain-tan a deer hide. We do not give home instructions with urine or dung.

FAQ

Why did tanners use urine? To loosen the hair on hides before scraping. One uncited explanation is that urine turns to ammonia.

Why did tanneries smell? They were called an "odoriferous trade". Today's odors come mainly from putrefying hides, hydrogen sulphide, ammonia and volatile organic compounds.

What are the different types of leather tanning? Plant tannins, chromium(III) salts, wet white with aldehydes or metal salts, and alum tawing. See what it means to tan leather.