Milk fibre; azlon (azlon is the generic name for all fibres made from regenerated proteins)
Inventor: Antonio Ferretti (1889–1955)
Patented: 1935
Commercially available from: 1936, Snia Viscosa, Italy
Trade names: Lanital; Aralac; Merinova; Fibrolane A; Chinon K-6 (modified casein fibre)
Commonly used starting materials: Casein from skimmed milk; and for modified casein fibre: acrylonitrile (derived from petrochemicals) and ammonia. For a simplified visual explanation of the process from starting materials to usable fibre please go to Fibre conversion processes: casein fibre.
Principal characteristics: soft, with a warm handle; good thermal insulation; light and comfortable to wear with a silky feel; it readily attracts water, making it vulnerable to mould in damp conditions when relative humidity exceeds 70%; in its original form it had poor wet strength.
Principal uses: initially developed as a wool substitute. Today it is often blended with other fibres and used for underwear and clothes worn against the skin. Global production is very small, and the fibre is expensive.
Environmental impact: depletion of fossil fuels, a non-renewable resource, due to the high-energy requirement for acrylonitrile production. Use of toxic chemicals and volatile substances that can harm the environment if not handled carefully. More positively, the fibre uses waste milk which would otherwise be poured away.
Care and signs of degradation: casein fibres are susceptible to microbiological growth. They accept dyes well but have poor wash-fastness. Casein fabrics need to be stored at a relative humidity level above 40%. Lower relative humidity can result in brittleness and breakage of fibres.
Recyclable? Potentially. Acrylic, which is also made with acrylonitrile, can be recycled in a way that prevents the materials from degrading. This means the process does not require the input of new materials. However, it is accepted by very few recycling contractors.
Biodegradable? Yes, when it is made with formaldehyde. No, if made with acrylonitrile.
Potential narratives:
- research into the production of alternative fibres as substitutes and in the pursuit of sustainability.
- the politicisation of textiles: the use of Italian manufactured milk protein fibre as a nationalist symbol by the Italian fascists in the late 1930s and during World War Two is an interesting example of this.
Documented garment exemplars:
- Purotatto top of MicroModal (lyocell) regenerated cellulose and casein fibre - see 2020s