Natural animal fibers, which consist mainly of keratin, take two forms: continuous fibers (filaments) and staple fibers.
Staple animal fibers are animal hairs which are commonly known as wool.
Four main species supply wool suitable for textile use:
- Ovine: different breeds of sheep. They produce most of the wool sold on the market.
- Goats: different breeds of goat. Depending on their specific characteristics, they produce mohair, cashmere and angora. (Rabbit hair is sometimes referred to as angora. However, rabbit farming is becoming increasingly rare following animal welfare concerns.)
- Cattle: yaks
- Camelids: camels, llamas, alpaca, guanacos, vicuñas, etc.
The only natural continuous fiber is silk.
This filament forms the cocoon of certain butterflies (notably the Bombyx of the mulberry tree).
Read also: Natural Plant Fibers
Wool is a special kind of mammalian hair. Consisting essentially of keratin, it protects Bovidae from bad weather.
An animal fleece is all the usable hair of an animal. Traditionally, wool refers to sheep fleece. However, fleeces from other animals, such as mohair wool (Angora goat) or cashmere wool (cashmere goat), are also known as wool.
This article focuses on sheep’s wool, which accounts for most of the world’s wool production.
Sheep are thought to be one of the first domesticated species; humans have been working with wool for around 10,000 years. Until the end of the 18th century, wool production was confined to European and Mediterranean regions. It then spread to the Southern Hemisphere, notably to Cape Town, Australia, New Zealand and La Plata which subsequently became the world’s leading producers.
The Merino breed of sheep, which produces the wool of the same name, has been developed through selection and cross-breeding to obtain the highest quality wool. The qualities of Merino wool include softness, fineness, evenness, elasticity, crimp and whiteness. The first Merino sheep were introduced to Australia in 1797. The country is now the world’s leading exporter, with wool production made up of 70% Merino wool.
Production and Processing
Intensive sheep farming is mainly practiced in countries in the Southern Hemisphere. A flock, which is on average 15,000 to 20,000 heads, is made up mainly of females and castrated males. Breeding is carried out by rams selected for the quality of their wool.
A sheep is shorn annually in spring and produces a fleece weighing 3-5kgs. The climate has a major influence on the quality of the wool. In dry areas, it will be more brittle (tender) and in wet areas, thicker and more resilient (sound).
The fleece is made up of two types of hair: guard hair (coarse surface hair) and down (fine, short, wavy hair). The latter is used as a textile fiber. The entire fleece after shearing retains its wax-like coating. This “wool grease” is a mixture of sweat, waxy ester (a protective greasy substance called lanolin) and various impurities (staining, vegetable matter, etc.).
Once the wool has been sorted and washed, it is delivered in bales (weighing 190kg in Australia) to brokers for initial classification. The aim is to create homogenous batches using batches from a large number of farms. Additional laboratory tests are carried out to provide certificates. With a certificate and sample of the wool, a buyer can gauge the quality of bales (the visual aspect, feel, fiber length and tenacity – tender or sound).
Classification and Characteristics
Sheep’s wool is divided into two categories: short-fiber (carded) wool and long-fiber (combed) wool, destined to be combed for long-fiber spinning.
The characteristics of wool vary greatly from one species of sheep to another. It is classified into four categories corresponding to the original breeds:
- Ultra fine wool (less than 26 microns): Merino
- Wool from fine crossbreeds (27-31 microns): Rambouillet, Bluefaced Leicester, Corriedales
- Wool from medium crossbreeds (23-34 microns): Columbia, Targhee, Finnsheep, Suffolk
- Thick crossbred wool (over 36 microns): Lincoln
The finest (highest quality) fibers are used for clothing, the medium fibers for household linen, and the thickest for carpets.
In addition to the type of wool (carded or combed) and the breed of sheep, fibers are classified by style (the area of the body from which they come, such as the fleece or the belly) and color (whiteness is traditionally favored).
The fineness and length of the fibers depend on the species. Thermoregulatory properties of the different wools relate to the altitude and temperature, for example, of the environment of the species. They also depend on the area of the body on which they have grown.
Wool is the only naturally curly fiber with a consistent elasticity and ability to be smoothed out. The fiber has shape memory when subjected to heat, steam, pressing or felting.
It is an extremely versatile fiber which, depending on how it is spun, woven, knitted and finished, can take on a wide variety of aspects: fine and fluid, soft, lustrous (after calendering), fluffy (after brushing), etc.
It is hydrophilic (it can retain 33% of its weight in water vapor), insulating and thermoregulating. Another advantage of wool is its easy-care attributes: it requires fewer washes than other fibers. Odors (from perspiration or other sources) are simply removed by airing the garment.
It is also anti-static, resistant to noise and vibrations, and flame retardant. Its long fibers make it easy to recycle, and it is naturally biodegradable.
The scaly structure of wool fiber makes it susceptible to felting. Felting is caused by a combination of four factors: water, heat, soap and mechanical movement. If left unchecked, felting can become a major drawback in the caring of finished products. If exposed to a lot of sunlight, wool discolors and can weaken. When wet, its strength decreases and it is prone to shrinkage. Rustic wools can also irritate the skin.
An overview of the properties of other animal hairs:
- Cashmere (cashmere goat): a supple, notably soft and light fiber with excellent thermoregulatory properties.
- Mohair (Angora goat): a fiber that is ultra-soft, shiny, light, fluffy and bulky.
- Yak: a fiber that is ultra-soft, resistant, light and thermoregulating
- Dromedary (domesticated): a fine, silky fiber. It is anti-static, repels dust and is a very good thermal insulator.
- Camel: a softer, finer and more abundant fiber than that of the dromedary.
- Llama (domesticated): a particularly soft, warm fiber (warmer than alpaca).
- Alpaca (domesticated): a particularly warm and soft fiber (softer than llama).
- Guanaco (wild ancestor of the llama): a fiber that is finer than that of the llama.
- Vicuña (wild ancestor of the alpaca): a luxurious fiber, superior in quality to that of the alpaca.
Impacts of production
Washing the wool before spinning requires the use of water, chemicals and energy.
Conventional wool production is also criticized for not respecting animal welfare, in particular the practice of mulesing. Now banned in several countries, the aim of this practice is to prevent the development of parasites that damage the animal’s health and wool production. ‘Mulesing free’ labels guarantee that the wool does not come from herds that have undergone this operation.
Read also: What are the fundamentals of animal welfare?
Silk is a filament produced (drooled) by butterfly caterpillars.
Only two butterflies produce silk that can be used in industrial spinning. The Bombyx mori worm produces the silk filament used mainly in the textile industry. The tussah silkworm, from the Antheraea pernyi butterfly, produces wild tussah silk.
The oldest fragments of silk date from around 2570 BC. Synonymous with luxury, its production was exclusively Chinese for centuries. It was exported throughout Asia and from the 4th century BC, Persian merchants used the Silk Road to spread trade in silk across Europe.
European production became industrialized in the 19th century, with Lyon becoming a hub of the silk trade. However, the European silk industry suffered a major decline due to several factors: silkworm epidemics, shortages, increasingly efficient Asian production and the arrival of artificial fibers.
Today, silk production represents a tiny proportion of global textile fiber production (0.15% in 2021). Nevertheless, its unique status makes this exceptional fiber a market worth several billion U.S. dollars.
China remains the world’s leading producer, accounting for over 60% of the market. It is followed by India and Uzbekistan.
Production and Processing
Silk production begins with silkworm rearing, or sericulture. This ancient and demanding practice is listed as an Intangible Cultural Heritage by UNESCO.
Sericulture encompasses all operations: growing the mulberry tree (the environment and food of the Bombyx mori butterfly), the rearing of the silkworm to obtain the cocoon, reeling the cocoon and spinning the silk.
Silkworm rearing takes an average of 32 days, during which time the worms grow and fatten through five stages, feeding on prodigious quantities of mulberry leaves. Specific conditions are essential to the good health of the worms: temperature, humidity, light and hygiene prevent the onset of the many diseases that can affect rearing. When the caterpillar reaches its fifth stage, it climbs into the branches to form its cocoon and transform into a chrysalis.
Eight to ten days after the cocoons have been created, they are removed from their support and sorted. The ‘blaze’, which holds the cocoon in place, is then removed. Next comes the stifling stage, during which the cocoons are placed in ovens at 70°C to 80°C, which kills the chrysalis without damaging the cocoon.
Next, they are placed in boiling water to be unwound. The cocoons are constantly stirred to find the end of the yarn, called slime. These first very fine yarns are reeled together in groups of around 10. As they cool, the yarns are welded together by sericin (the soluble varnish that envelops them). The yarns thus obtained are raw silk.
Next comes the molding process, which involves assembling several raw silk yarns and twisting them together. The twisting may result in the creation of different types of yarn (e.g. silk crepe, organza and grenadine).
Silk is divided into several qualities.
Raw silk is the highest quality. It uses only a third of the yarn’s original length and produces a fine, shiny yarn. Wild silk (shantung) from non-domesticated Bombyx species such as tussahs, has a thicker, more irregular yarn.
The second quality, known as chappe silk, is made from silk floss (waste after reeling). A third quality, bourette silk, is characterized by very short fibers and the presence of knots.
The grade of the silk is expressed by a series of two numbers (e.g. 9/11, 16/18, 20/22). A 9/11 silk, for example, indicates that the titre of the silk yarn is 9 to 11 deniers.
Silk is renowned for its softness, fineness and shine. It is also one of the most robust fibers.
Depending on how it is spun, it can have good elasticity and be easily crease resistant. Its ability to absorb water means it can take vivid colors. Silk is also a good moisture regulator, and naturally eliminates dust and dirt.
Silk is a poor conductor of heat and tends to collect static electricity. It also has a tendency to shrink, and is sensitive to sunlight and sweat.
Impacts of production
Although silk is a natural and biodegradable material, its cultivation is not without impact. Intensive sericulture involves the use of chemicals, pesticides and fertilizers, as well as working conditions that do not always meet international standards. Animal welfare campaigners also criticize the treatment of the worms (with antibiotics and hormones), as well as the fact that they are scalded with boiling water while still developing.
Alternatives to conventional silk are emerging, such as organic silk and peace silk, which is produced without killing the chrysalises.
The textile manual, Fashionary, 2020
Le dictionnaire des textiles, Maggy Baum et Chantal Boyedieu, 2006