Composition states which fibres a cloth contains and in what proportion by weight, listed in descending order. "65% Polyester 33% Viscose 2% Elastane" is a complete and precise statement about content. What it is not is a description of the fabric.
What the percentages actually change
Read the dominant fibre first: it sets breathability, moisture behaviour, care requirements and much of the cost. A cloth that is majority cotton behaves like a cotton cloth even with a substantial synthetic content.
Then read the minority fibres, which are usually there for a specific reason. Polyester in a wool blend improves crease recovery and reduces cost. Viscose in a linen blend adds drape. Cotton in a linen blend softens the hand. None of these are dilutions; they are engineering decisions.
Elastane deserves its own paragraph
Two to three percent elastane transforms a fabric out of proportion to its share. It adds comfort stretch and recovery, changes how a garment fits through a day, and simultaneously changes shrinkage, pressing behaviour and the sewing setup. A cloth with elastane needs a different needle, a different stitch and different heat settings.
It also has consequences the buyer inherits later: elastane degrades with high heat and with chlorine, so a garment with elastane cannot carry the same care instructions as one without. If a composition line shows elastane and the care label does not reflect it, someone has not read the specification.
What composition does not tell you
- Not stated
- Yarn count — the biggest driver of hand and price
- Not stated
- Construction — woven or knitted, in which structure
- Not stated
- GSM — weight, and therefore application
- Not stated
- Finish — washing, brushing, coating, mercerising
This is the practical point. Two cloths can share an identical composition line and be entirely different products: 100% cotton describes both a 90 GSM voile and a 400 GSM canvas. Composition is one line of a specification, not the specification.
Reading a line in practice
- Dominant fibre: sets the character and the care.
- Minority fibres: ask what each is there to do.
- Elastane: assume it changes shrinkage, pressing and care.
- Then ask for count, construction, GSM, width and finish.
A supplier who answers all five without hesitation is describing a real article. One who can only quote the composition is describing a category.
Where composition becomes a legal statement
Fibre content is regulated in most markets, and the percentages on a label carry legal weight rather than being a marketing description. Tolerances are narrow, the declaration has to reflect what is actually in the cloth, and a garment mislabelled at the fibre stage is a problem that follows the brand rather than the supplier. For a buyer this has a practical consequence: take the composition from the supplier’s technical documentation for that specific article, not from a category page or a previous season’s spec, and confirm it has not changed when an article is reordered.