Introduction
Every sourcing decision in woven fabrics begins with one line on the specification sheet: composition. "100% cotton" tells you only the headline. The useful questions are underneath: What kind of cotton? What happens to the hand-feel, shrinkage, pilling and price if 2% elastane or 35% polyester is added? How can I verify what the mill actually wove? And what does the law require my label to say in Berlin, Boston or Sydney?
Fiber content drives roughly half of a fabric's behavior — moisture absorption, breathability, wrinkle recovery, strength, dye behavior, thermal character, care requirements and cost. The weave, yarn and finishing drive the other half, which is why two "100% cotton" fabrics can feel like different species: a 90 GSM combed voile and a 400 GSM canvas share the same fiber but nothing else.
This guide gives apparel and home-textile buyers a practical grip on the six fibers that dominate cotton-rich woven sourcing from China — cotton, polyester, viscose/rayon, linen, nylon and elastane — explains how blend ratios move the needle on the properties you care about, shows how composition is identified (from a quick burn test to ISO chemistry), and summarizes EU, US and UK labeling rules. Our related guide explains where these numbers live on the document you negotiate: how to read a fabric specification sheet.
1. Natural vs Man-Made Fibers: the Two Families
All textile fibers fall into two families, and the family predicts a lot of behavior:
- Natural fibers grow on plants or animals: cotton (seed hair), linen/flax and hemp (bast/plant stem), wool, silk. They absorb water readily, breathe, dye with familiar cotton or wool dye classes, tend to wrinkle, and can be attacked by mildew and moths.
- Man-made (chemical) fibers are extruded. They split into cellulosic regenerated fibers — viscose/rayon, modal, lyocell (Tencel), made from dissolved wood pulp, so they behave partly like cotton — and synthetic fibers — polyester (PES), polyamide/nylon (PA), acrylic, polypropylene — made from polymers. Synthetics are strong, thermoplastic (they melt and can be heat-set), low-absorption, wrinkle-resistant and prone to oil-based soiling and static.
Elastane (EL, spandex, Lycra® is a brand) sits with the synthetics but is used only in small percentages as a stretch engine. In the cotton and cotton-blend wovens a Keqiao mill ships for shirts, trousers, jackets, quilts and home textiles, the recurring cast is cotton, polyester, viscose, linen and 1–5% elastane; nylon appears mainly in blended performance and stretch fabrics.
2. Fiber-by-Fiber Profile
Cotton — the reference fiber
Cotton is a cellulose seed fiber. Comfort properties are excellent: moisture regain is about 7–8% in standard atmosphere and it can absorb far more water before feeling wet; it conducts heat and air, feels comfortable against skin, and accepts reactive and vat dyes for deep, fast shades. Its weaknesses: it wrinkles easily, shrinks when relaxed in water unless sanforized or pre-washed, dries slowly, can mildew when stored damp, and costs are tied to volatile cotton futures and lint quality. Staple length matters — long-staple/combed cotton (including Pima/SUPIMA and extra-long staple types) spins finer, stronger, neppier-free yarns for premium poplin; carded open-end yarn is cheaper and duller. Organic and BCI/regenerative programs add chain-of-custody requirements and premium rather than a different physical fiber.
Polyester (PES) — strength and stability
Polyethylene terephthalate filament or staple is the world's most-used fiber. It is strong wet and dry, abrasion-resistant, dimensionally stable (very low shrinkage after heat setting), quick-drying, wrinkle-shedding and inexpensive. Its comfort deficits: low moisture absorption (regain ~0.4%), static, a slick or papery hand in cheap constructions, oil-stain affinity, and pilling when staple-spun in blends. In wovens, polyester is blended with cotton for easy-care shirting and uniforms (TC 65/35, CVC 60/40), used as filament for linings and satins, and used in microfiber and recycled (rPET/GRS) qualities. Dyeing requires disperse dyes at high temperature; polyester cannot be dyed with cotton reactive dyes, which matters when a blended fabric needs cross-dyeing in two shades.
Viscose / Rayon — the fluid drape fiber
Viscose (called rayon in US nomenclature; modal and lyocell are improved regenerated-cellulose cousins) is wood pulp reborn as filament. It breathes and absorbs like an exaggerated cotton — regain ~13% — with fluid drape, silky luster and a soft, cooling hand. Its weakness is the price of that drape: wet strength drops sharply, it shrinks and creases easily, and poor-quality constructions can bag or distort; it also needs gentle wash care or dry cleaning in fine garments. Linen-viscose and cotton-viscose blends are mainstream in women's and summer wovens; sand-washed finishes on linen-viscose are a popular Keqiao line (see our linen-viscose buyer's guide). Viscose is cellulose and dyes like cotton, but burns like paper too, which is why hand identification of viscose vs cotton needs a microscope, not a lighter alone.
Linen (flax) — crisp and cool
Linen is a bast fiber, long and irregular. It is the strongest of the common natural fibers, highly conductive and cool to touch, very absorbent (regain ~12%), naturally lint-free and slubby, with an unmistakeable crisp, textured hand that softens with washing. It wrinkles notoriously, has low elasticity (it creases and stays creased), sheds lint when new, and costs more than commodity cotton. Pure linen also tends to shrink more than cotton in the first washes unless well pre-washed. Blending 30–55% linen with cotton keeps the dry, breezy character while taming cost, wrinkle rage and shrinkage — the linen-cotton shirt and dress cloths are among the most practical warm-weather wovens on the market.
Nylon / Polyamide (PA) — toughness and stretch recovery
Polyamide fibers (nylon 6 and 6,6) are synthetics prized for exceptional strength-to-weight, abrasion resistance, elasticity and recovery. They absorb slightly more moisture than polyester (regain ~4%), accept acid dyes in bright shades and are common in performance taffetas, taslan, ripstop, swim and active linings. In cotton-rich woven apparel, nylon appears in compact blended stretch fabrics and in sewing/embroidery threads rather than as the dominant fiber; it is thermoplastic, melts around 210–220 °C and can glaze under a too-hot iron.
Elastane (EL / Spandex / Lycra®) — the 2% that changes everything
A polyurethane segment copolymer with extreme elongation (5–7×) and recovery. Used at 1–5% in wovens: 1–2% gives comfort stretch in shirting and chinos; 2–3% gives the stretch in stretch corduroy and stretch twill; 3–5% plus a compatible weave construction approaches power stretch. Elastane is always delivered wrapped or co-spun with another fiber in woven yarns (core-spun cotton around an elastane core). It raises cost, adds a heat ceiling (do not set commercial irons above roughly 150 °C; heat damages spandex), imposes bleach restrictions (chlorine degrades it), and complicates recycling claims — a fabric with 2% elastane is not "100% cotton" even if it looks and feels like it.
| Fiber | Family | Moisture regain (typical) | Hand/character | Weaknesses | Care ceiling |
|---|---|---|---|---|---|
| Cotton | Natural (cellulose) | ~7–8% | Soft, breathable, familiar | Wrinkles, shrinks if untreated, mildews wet | Hot iron ~200 °C |
| Polyester | Synthetic | ~0.4% | Crisp/slick, stable, quick-dry | Static, pills, oil stains, heat-set shine | Low-medium ~150 °C |
| Viscose/rayon | Regenerated cellulose | ~13% | Fluid drape, soft, cool, lustrous | Weak wet, shrinks, creases | Gentle; medium iron damp |
| Linen | Natural bast | ~12% | Crisp, cool, slubby, strong | Wrinkles heavily, initial shrink/lint | High ~200–220 °C damp |
| Nylon | Synthetic | ~4% | Tough, smooth, elastic | Melts/glazes, UV aging, static | Low ~110–150 °C |
| Elastane | Synthetic (PU) | ~1% | Invisible stretch engine | Heat/chlorine/oil damage; small % only | ≤ ~150 °C, no chlorine bleach |
3. Blend Ratios: How the Percentage Moves Performance
Blending exists because no single fiber does everything. Typical woven blends and what the ratio buys:
| Blend | Common ratios | What the blend delivers | Typical end use |
|---|---|---|---|
| Polyester–cotton (TC/CVC) | 65 PES /35 C (TC); 50/50; 60 C/40 PES (CVC) | Easy care, less ironing, strength, lower cost; more cotton = more comfort and breathability | Uniforms, workwear, budget shirting, bed linen ranges |
| Cotton–elastane | 98/2, 97/3 | 10–30%+ stretch with cotton look; improves fit and crease recovery | Stretch poplin shirts, chinos, stretch corduroy |
| Linen–cotton | 55 L/45 C, 30/70, 70/30 | Dry texture and coolness with controlled shrink, softer hand, better price | Summer shirts, dresses, relaxed trousers |
| Linen–viscose | 55/45, 50/50 | Drape and fluidity added to linen character; sand-wash enhances softness | Women's dresses, skirts, loose trousers |
| Cotton–viscose | 70/30, 50/50 | Drape and luster with cotton's wet stability; softer than pure cotton | Blouses, dresses, lining-adjacent cloths |
| Nylon–cotton/elastane | small PA + 2–4 EL | Toughness, recovery, abrasion in stretch fabrics | Performance trousers, outdoor-adjacent wovens |
| Recycled/other fibers | rPET, recycled cotton, hemp blends | Sustainability claims (need GRS/RCS chain of custody) | Eco collections, certified programs |
Three ratio truths worth internalizing. First, the majority fiber sets the dominant care and labeling regime, but a 2% minority can set the heat ceiling (elastane) or the dry-clean recommendation (metallic/finishing fibers). Second, hand-feel can be engineered by finishing — sanding, peach, enzyme, silicone and compacting can make a poly-cotton feel far more natural than its ratio suggests, which is why hand alone never verifies composition. Third, ratios are by mass, conditioned — a 55/45 linen-cotton is 55% linen by weight, and percentages must match the label within legal tolerances.
4. Identifying What You Actually Received
Three levels of certainty, cheapest first.
Level 1 — The Burn Test (screening only)
Ravel a few yarns from warp and weft (blends can differ by direction!), tease fibers from the yarn, and hold with tweezers in a flame away from drafts. Cellulose (cotton, linen, viscose) ignites quickly, burns with a yellow flame and smells like burning paper, leaving fine gray ash. Linen behaves like cotton but with less curl; viscose burns fast with very little ash. Protein fibers (wool, silk) burn slowly, self-extinguish, smell like burning hair and leave crushable black bead ash. Synthetics curl away from the flame, melt and drip, and form hard round beads — polyester gives a sweetish chemical smell and hard black/cream bead; nylon smells faintly celery-like with a hard gray bead; elastane does not support flame alone and melts rubberily. A blend burns and leaves both ash and hard bead — the bead's presence flags synthetic content even when the mill said "100% cotton."
Limits: burn tests cannot separate cotton from linen or viscose reliably, cannot quantify percentages, and finishes/sizing distort smell and flame. Use it as a dock-side lie detector, not a certificate.
Level 2 — Microscopy (qualitative ID)
Under a compound light microscope (100–500×) with longitudinal and cross-section mounts, fibers are identifiable by shape: cotton is a flattened, twisted ribbon with occasional convolutions; linen is cylindrical with cross-markings ("nodes") and narrow lumen; viscose has smooth, glassy longitudinal striations and irregular cross-sections; polyester and nylon are smooth, uniform rods with round or lobed cross-sections; wool shows scales; silk is smooth twin triangles. A trained lab distinguishes cotton/linen/viscose mixtures qualitatively and estimates blend presence — a common ISO reference is ISO 137 for wool and the fiber-identification family of methods, AATCC 20 in the US.
Level 3 — Quantitative Chemical Analysis (the enforceable result)
For percentages you put on a legal label, laboratories dissolve each component in sequence with selective reagents and weigh the residue under controlled conditioning: ISO 1833 series (e.g. sulfuric-acid methods for cotton/viscose/polyester systems, acetone for acetate, etc.) or AATCC 20A. Common Keqiao and international labs issue a composition report with percentages by weight and method; results carry a small agreed tolerance (analytical and manufacturing variability, often around ±3 percentage points in commercial practice, stricter under EU rules — see below). When ordering: test warp and weft separately if you suspect one-direction blends, condition samples properly, and test bulk production rolls sampled by an inspector, not show-room swatches.
Quick non-destructive tells
- Water drop: cellulose absorbs immediately; polyester beads and spreads slowly.
- Iron/heat test on a scrap: polyester and nylon can glaze or shrink under high heat; cotton/linen take it.
- Stretch check: persistent bidirectional stretch beyond weave give implies elastane in one or both yarn systems.
- Wrinkle recovery: crush in hand for 30 seconds; high-polyester blends spring back, linen stays, cotton partially recovers.
5. Labeling Laws: What Composition You Must Declare
Composition is one of the few textile attributes governments force you to label accurately. Requirements differ by market but share a backbone: label all fibers by generic name, descending percentage by weight, with tight tolerance against reality.
European Union — Regulation (EU) No 1007/2011
Textile products sold in the EU need labels or markings giving full fiber composition in the official language(s) of the member state. Only the harmonized fiber names in the regulation's annexes may be used (e.g. "cotton," "polyester," "elastane," "viscose" — not marketing-only names). Rules that matter to buyers:
- Percentages are by total fiber weight; a tolerance exists only for unavoidable manufacturing variation or agreed additives — about 3% of total weight is the practical allowance; labels must not systematically overstate.
- Fibers under 5% may be listed as "other fibres" individually or collectively (except wool, which has special thresholds), but elastane present at functional levels should be declared explicitly for consumer trust and care accuracy.
- Decorative fibers below thresholds, anti-static components and similar have specific exemptions/declaration rules — check the regulation for multi-component garments.
- Multi-component products follow rules on label content per component (outer fabric, lining, filling).
- Animal-origin non-textile parts (fur/leather) carry separate "contains non-textile parts of animal origin" labeling where applicable.
United States — Textile Fiber Products Identification Act (TFPIA), enforced by the FTC
Labels must show the generic fiber names (the FTC-approved list: cotton, polyester, spandex, rayon, linen, nylon…) and percentages by weight in descending order; a tolerance of 3 percentage points for non-functional components is recognized in practice, while fiber amounts under 5% may be listed as "other fiber" unless the fiber has a functional claim. The label must also carry manufacturer/marketer identity (RN or name) and country of origin (separately governed by CBP origin rules). "Rayon" is the accepted US generic for viscose; "lyocell" and "modal" are now also recognized generic names. Brand names (LYCRA®, TENCEL™, SUPIMA®) may appear only alongside the required generic term and only under license.
United Kingdom and other markets
The UK retains its Textile Products (Labelling and Fibre Composition) Regulations, closely mirroring the EU 1007 framework with prescribed fiber names and percentages. Canada (Textile Labelling Act), Australia/New Zealand care-labeling rules and Japan's household goods labeling law all require fiber content by generic name and percentage; details and language requirements vary, so have your importer or test lab confirm the exact wording per destination. For piece goods sold to a garment factory (rather than retail), commercial composition declarations and spec sheets govern; the consumer-label obligation crystallizes when the sewn product is sold, but the accuracy of your declared composition is what makes your customer's label legal.
What this means operationally
- Put composition with method-backed percentages on the purchase contract and spec sheet, not just WeChat messages.
- Keep a quantitative test report for each new bulk construction (and periodically for repeats) in your compliance file.
- Never let a sales team round "80/20-ish" to 80/20 on labels; never print "100% cotton" on elastane-containing stretch cloth.
- For certification claims (organic/GOTS, OCS, BCI, GRS recycled polyester/cotton), collect scope and transaction certificates through the whole chain — standard composition reports do not prove a sustainability claim. Our certifications guide walks through those documents.
6. Why Composition Drives Price and End Use
Fiber is the largest single variable in yarn cost. Typical drivers:
- Raw material markets: cotton tracks ICE futures and the quality premium (combed, long staple, organic, BCI); polyester tracks PTA/MEG and oil; linen costs reflect limited flax processing capacity, largely European; man-made cellulosics track pulp and specialty premiums (modal, lyocell cost above commodity viscose).
- Spinning complexity: fine combed counts, core-spun elastane, blends with incompatible fibers, and compact/siro spinning all add cost per kilogram of yarn.
- Dyeing chemistry: blends often need two-bath or cross-dyeing (reactive for cotton + disperse for polyester), longer cycles and more energy than single-fiber cloth; nylon needs acid dyes; deep shades on polyester require high temperature or pressure.
- Yield: fiber density changes meters per kilogram — light synthetics yield more length per unit weight, which is why per-kg comparisons between compositions mislead; always compare woven price per meter at fixed GSM and width.
Matching composition to end use prevents the most common commercial mistake — over- or under-specifying. Examples from our own range: a breathable children's shirt wants 100% combed cotton poplin or a 98/2 stretch poplin, not a 65/35 TC; a school uniform program often wants CVC/TC for wash-and-wear durability and budget; a structured jacket or apron wants heavy cotton canvas/twill (canvas series here); a fluid women's dress belongs in linen-viscose or sand-washed blends; winter outerwear and home goods are where quilted cotton constructions face or back natural cloth over batting; corduroy is nearly always 100% cotton or cotton with 2–3% elastane in stretch qualities.
7. Sourcing Notes from a Keqiao Cotton Mill
In Keqiao's market, "cotton" quotations deserve three clarifying questions: carded or combed? ring-spun or open-end? and is the quoted blend by the finished fabric or by yarn purchase? Because fabric pricing is quoted per meter while yarn is bought per kilogram, some confusion is genuine — and some is strategic. At Mujia Textile, cotton and cotton blends are the core of the catalog (poplin, corduroy, canvas/twill, linen-cotton, quilted and digital print), and every shipment's spec sheet states composition with percentages, supported by in-house and third-party testing of bulk rolls. Typical practices: composition confirmed by quantitative analysis for first orders and claims programs; elastane percentages and core-spun construction declared on stretch lines; GRS/GOTS/OCS claims supported by valid scope and transaction certificates rather than sticker logos. For a first read on the full range of cotton constructions and weights, see the complete cotton fabric types and weights guide.
Composition Verification Checklist
- [ ] Contract names every fiber, percentage by weight, yarn type (carded/combed, ring/OE)
- [ ] Burn test at sample and at receiving for synthetic-bead screening
- [ ] Quantitative lab report (ISO 1833 / AATCC 20A) from bulk-roll sampling on new constructions
- [ ] Warp and weft tested separately where stretch or one-way blends suspected
- [ ] Care symbols and iron/bleach limits matched to the most sensitive fiber present
- [ ] Labels drafted per destination: EU 1007/2011 generic names; US TFPIA generic names + RN + origin; UK/CA/AU equivalents
- [ ] Brand names (LYCRA®, TENCEL™, SUPIMA®) used only with valid license evidence
- [ ] Sustainability claims backed by scope + transaction certificates (GOTS/OCS/GRS/BCI)
- [ ] Price compared per finished meter at fixed width/GSM, never per kg across different fibers
Mujia Textile (mujiatextile.com) is a factory-direct cotton and cotton-blend woven fabric maker in Keqiao, Shaoxing. We declare exact composition and blend ratios on every spec sheet, support third-party testing on production rolls, and carry certified options for organic, BCI and recycled-fiber programs. Send us your target hand-feel, end use and label requirements — we will match the fiber, blend and finish and ship swatch cards worldwide.