Here is a detailed explanation of the historical use of liquefied pigeon droppings in leather tanning, focusing on the 19th-century practices in Morocco and Victorian England.
Introduction: The Value of the Unpleasant
In the 19th century, leather was a ubiquitous material, as essential to daily life as plastic is today. It was used for shoes, belts, horse tack, industrial drive belts, bookbinding, and armor. However, transforming a raw, rotting animal hide into supple, durable leather required a long, complex chemical process.
One of the most critical—and most repulsive—steps in this process involved the use of liquefied pigeon droppings. This substance, known in the trade as "pure" or "bate," was a highly valued commodity in both the ancient tanneries of Fez, Morocco, and the industrial slums of Victorian London.
The Science: Why Pigeon Droppings?
To understand why tanners used bird feces, one must understand the chemistry of tanning.
- De-hairing (Liming): Before a hide could be tanned, the hair and flesh had to be removed. This was usually done by soaking the skins in a solution of lime (calcium hydroxide) or urine. While effective, the lime left the skin highly alkaline, swollen, and brittle. If tanned immediately in this state, the leather would be hard and prone to cracking.
- Bating (The Pigeon Step): The hides needed to be neutralized and softened. This is where the pigeon droppings came in. The droppings were mixed with water to create a slurry.
- Ammonia: The droppings were rich in ammonia, which acted as a neutralizing agent against the alkaline lime, bringing the pH of the skin down.
- Enzymes: More importantly, the feces contained proteolytic enzymes (bacteria produced in the bird's gut). These enzymes digested specific proteins in the skin (like elastin) without destroying the collagen fibers that give leather its strength.
The result was a skin that was "flaccid" and silky to the touch, ready to absorb the vegetable tannins (usually oak bark or sumac) that would preserve it permanently.
Context 1: The Tanneries of Fez, Morocco
In Morocco, specifically in the city of Fez, the Chouara Tannery has been operating since the 11th century. The methods used in the 19th century—and which are still largely used today—relied heavily on pigeon droppings.
- The Vats: The tanneries are composed of a honeycomb of stone vessels filled with various colored liquids. The white vats contained the mixture of cow urine, quicklime, water, and salt (for stripping hair). The adjacent vats contained the pigeon droppings.
- The Process: Tanners would stand waist-deep in the murky mixture of water and pigeon feces, kneading the skins with their bare feet for hours. This manual agitation ensured the enzymes penetrated the fibers of the hide thoroughly.
- The "Moroccan Leather" Reputation: This specific process was crucial to the creation of "Morocco Leather"—a soft, pliable goatskin often dyed red or yellow, which was prized worldwide for bookbinding and luxury goods. The wild pigeon droppings were considered superior to other manures because of their specific chemical potency.
Context 2: Victorian England and the "Pure Finders"
In 19th-century London, the demand for leather was driven by the Industrial Revolution. Bermondsey, a district in South London, became the capital of the leather trade. However, sourcing enough chemical agents for this massive industry created a bizarre micro-economy.
The "Pure Finders"
The demand for dog and pigeon excrement was so high that it spawned a specific profession: the Pure Finder. Documented by the sociologist Henry Mayhew in his seminal work London Labour and the London Poor (1851), these were impoverished individuals who scoured the streets for feces.
- The Name: The substance was called "pure" because of its cleansing and purifying effect on the leather.
- The Collection: Pure finders—often elderly women—would roam the streets with a bucket and a glove (or sometimes just their bare hands), collecting fresh droppings. While dog dung was the primary commodity (known as "album graecum"), pigeon droppings were also highly sought after, particularly for finer, more delicate leathers.
- The Economics: A bucket of "pure" could fetch a decent price from the tanyards of Bermondsey. It was one of the few ways the destitute could earn a living, highlighting the stark contrast between the luxury of the finished leather goods and the squalor required to produce them.
The Decline of the Practice
The use of pigeon and dog droppings began to decline in the late 19th and early 20th centuries due to the advancement of chemical engineering.
- Hygiene and Health: As germ theory became understood, the health risks to tanners standing in vats of feces became unacceptable. The risk of anthrax and other infections was high.
- Artificial Bates: In the early 1900s, chemists synthesized artificial bating agents using pancreatic enzymes from animals (like trypsin) and ammonium salts. These provided a consistent, controllable, and sanitary alternative to the unpredictable chemical makeup of bird droppings.
Summary
The use of liquefied pigeon droppings in 19th-century Morocco and England serves as a fascinating example of pre-industrial chemistry. It was a process born of trial and error that utilized waste products to create luxury goods. Whether in the sun-baked vats of Fez or the smog-choked tanneries of London, the ammonia and enzymes found in pigeon feces were the secret ingredient that made Victorian leather the material that built an empire.