Who would imagine that a fabric made from a tree could be soft and flowing, cool and comfortable, and need little ironing? Who would imagine that a pair of jeans could feel like they were made of silk, rather than denim? And who would imagine that a sheer, silk-like shirt could be chucked into the automatic washing machine, rather than being washed by hand?

We are used to the idea of something soft yet strong coming out of a silk-worm's bum and something warm and fluffy coming off a sheep's back, but we have the prejudice that any fabric whose manufacture involves toxic chemicals is going to be synthetic, and therefore hot, sweaty and uncomfortable to wear. One exception is lyocell, a material that has natural origins and many unique properties. It should not be confused with viscose, which is quite different.

What Is this Fabric Made from?

Lyocell drapes well, is extremely soft to the touch, but yet is hard wearing and machine washable - an odd combination in a fabric.

Most people assume that there are two kinds of fibres: natural ones, like cotton, wool and silk; and artificial ones synthesised out of petrochemicals like nylon and polyester. Lyocell falls somewhere in-between. The raw material for lyocell is cellulose, which is broken down chemically and reformed as fibres. Trees are 50% cellulose, cotton is 90% cellulose, so lyocell is more accurately described as a recovered or regenerated fibre.

How Lyocell is Made?

Lyocell is a completely new kind of fibre, the first to be developed for over 30 years. It is formed by dissolving cellulose fibre, in the form of recycled paper, in the solvent referred to 'amine oxide'¹. Basically this involves chopping up large rolls of paper very finely and stirring them into a vessel full of the clean solvent.

Dissolution in amine oxide alters the chemical and surface properties of the cellulose, which is reformed into fibres by passing the solution through very finely machined holes in a steel plate. These holes are called 'spinneretes' - which is the same term used for the silk-producing organs on spiders and caterpillars - and their precise design and manufacture is critical to the successful formation of filaments.

Advantages and Disadvantages of Lyocell

One of the great selling points of lyocell is the environmentally friendly nature of the manufacturing process. The raw material is low-grade recycled paper. The solvent is almost completely recycled, with almost no losses to the environment. This has as much to do with the fact that it is highly toxic and costs about £15,000 per tonne, as it has to do with any environmental altruism on the part of the manufacturers.

It is very strong when wet - stronger than cotton. It also doesn't stretch or shrink when wetted or dried, unlike cotton or viscose.

The main disadvantage of lyocell fibre is its relatively low surface energy, which makes it difficult for dyes to bind to it. This is not to say it is impossible to dye - but the dyes required are more expensive. This tends to make the finished product more expensive.

It also has a tendency to fibrillate during processing and wearing. Fibrillation is what causes the effect known as 'pilling', where small balls of fibre form on the surface.

However, this is a relatively small price to pay for the unusual properties of this fibre.

So Who Invented it?

The original process was devised by Akzo Nobel and then licensed to Courtaulds during the 1970s. Akzo Nobel weren't in a position to develop it further and Courtaulds then developed a stable and controlled process to produce the first lyocell fibre in the late 1980s - their brand name is 'Tencel'.

Subsequent work by Courtaulds led to the development of Tencel A100. This is a non-fibrillating version of Tencel. Dye yields for Tencel A100 are excellent in comparison to other fibres including standard Tencel, cotton, viscose and most other fibres, producing brighter and more vibrant colours through using less dye. Colourfastness is also good.

Where Can I Get Some?

Lyocell is the generic name for the type of fibre. The trade name under which it is most commonly available is Tencel, a trademark of the manufacturer, Acordis (formerly Courtaulds, now a part of Akzo Nobel). Lenzing also makes an alternative lyocell fibre.

Many garments are available in these fabrics, from major clothing outlets. Tencel should not be confused with Tactel, which is a DuPont product with quite different characteristics.

The future of the fibre looks set to be interesting. In theory lyocell could come to replace much of viscose and polyester production and can even substitute for cotton. The process is environmentally friendly (at least as far as it is possible to be), whereas polyester is made from oil and viscose involves regenerating the fibre in an acid bath. The process is also more compact and reliable than cotton production, which is prey to weather conditions and also uses large areas of expensive land.