Modal is not polyester, and the difference is the tree
Modal confuses people, and reasonably so. It is not picked from a field, it comes out of a chemical process, and the resulting fabric feels closer to a synthetic than to a cotton jersey. So it is fair to ask whether a brand promising no polyester is quietly doing something similar under a nicer name.
The short answer is no, and the difference is where the carbon comes from.
Two different starting points
Polyester is polyethylene terephthalate. It starts as petroleum, is polymerised into a plastic, and is extruded into filament. When it degrades it degrades into smaller pieces of plastic. There is no stage at which it stops being plastic.
Modal starts as beech pulp. The cellulose is dissolved, forced through a spinneret and regenerated back into fibre. The chemistry is industrial and the fibre would not exist without it, but what comes out the other end is still cellulose, the same polymer that makes up cotton and linen and the tree it came from. It is biodegradable. It does not shed plastic when you wash it.
That is why the category is called regenerated cellulose rather than synthetic. The material is natural, the process is manufactured, and both halves of that sentence are true at once. Viscose, rayon, lyocell and modal are all variations on the same idea.
Where the honest edge is
Calling modal natural without qualification would be overstating it, so here is the qualification.
The older viscose process uses carbon disulphide, which is genuinely hazardous to the people working with it, and historically much of the industry was not careful about that. Modal is a modified process with higher recovery rates, and lyocell is a further step with a closed-loop solvent system that recovers upward of ninety-nine per cent. Producer matters enormously here. A modal from a mill with proper recovery is a very different object from one produced without it, and the label will not tell you which you have.
Forestry matters too. Beech is a renewable input only if the forest is managed as one, and some viscose production has been traced to ancient and endangered forest. There are certification schemes that address this. They are not perfect and they are considerably better than nothing.
A fibre is not good or bad. A fibre made a particular way, by a particular mill, from a particular forest, is good or bad. Most marketing is written to stop you asking which.
Why we use it at all
Modal does something cotton does not. It is finer, it drapes rather than holds, and it keeps that drape through repeated washing where a cotton jersey of the same weight would gradually go slack. For a fitted garment that is the difference between something that follows a body and something that hangs off it.
Our winged tee is ninety-five per cent modal and five per cent elastane. The elastane is synthetic and is there for recovery. We could have left it out and the garment would have fitted worse and stretched out at the seat within a season. That trade is stated on the product page rather than buried, because a standard you only mention when it is convenient is not a standard.
What we will not do is print the word natural on a modal garment and leave it there. It is regenerated cellulose. It is not plastic. Those are the two facts that matter, and they are enough on their own without dressing them up.
Sources
Everything above that is a claim about the world rather than about us is checkable here. If we have got something wrong, we would like to know.
- Lenzing, Chemicals used in fibre production the producer’s own account of the solvents in each process.
- Closed-Loop Technologies in the Viscose Process, Birla Cellulose carbon disulphide in viscose against NMMO with water in lyocell.
- CanopyStyle the initiative auditing whether dissolving pulp comes from ancient or endangered forest.