The "100% Cotton" T-Shirts Pilled and Stretched Out at the Neck After Three Washes

Fabric Fiber Composition Verification Guide

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A Korean brand selling basic T-shirts online had a knit garment factory in Shantou (汕头), Guangdong make short-sleeve tees. The label read "100% cotton, 20s single jersey, fabric weight 180 g/m²." The first 3,000 pieces sold well, so three months later the brand reordered 8,000 in more colors from the same factory. The pre-shipment inspection passed on dimensions, stitching, print, labels and packaging, and the factory also sent the fabric mill's fiber content test report.

About a month after the second batch went on sale, the reviews changed. "It pilled after three washes," "the neckline stretched out and I can't wear it," "it doesn't absorb sweat and feels sticky." The brand sent remaining stock to a lab: cotton was only 63%, and the other 37% was polyester. Fabric weight was 162 g/m², lighter than spec. To save on fabric cost, the factory had used TC (cotton/polyester blend) fabric instead of cotton.

Fiber content problems are a headache because you can hardly tell by looking at or touching a finished garment. A 100% cotton tee and a 65% cotton tee feel and look almost the same when new. The difference only shows after a few wears and washes, as pilling, stretching and poor moisture absorption. This article covers how to check fiber content, labeling tolerances, the substitutions factories commonly make, and how to build fiber checks into your spec sheet and inspection checklist, from a practical sourcing perspective.

The "100% cotton" on the label and the fabric mill's test report are not enough. Put fiber type and content, yarn count, fabric weight and test method into the spec sheet as numbers, and send garments you pick yourself from production to a lab. That is how you prevent fiber labeling violations and pilling and stretching claims.

1. Why Garments Fall Apart Quickly When Fiber Content Changes

Most of a garment's properties come from the fibers in its yarn. Cotton absorbs sweat well and feels soft on the skin, but wrinkles easily. Polyester is strong, dries fast and is cheap, but it does not absorb sweat, and because the fiber is so strong, pills that form stay on the surface instead of falling off. Blending polyester into a cotton tee lowers cost, but the moisture absorption and hand feel the customer expected disappear and pilling increases.

Factories trying to cut cost go first for the share of expensive fibers. In wool knits they lower wool content and fill with acrylic or nylon; in linen shirts they blend in rayon or cotton. Cashmere blends sometimes use fine sheep's wool or yak hair instead of cashmere altogether. Even with the same composition, switching to a coarser yarn or a lighter fabric makes the garment thinner and quicker to stretch, so check those as well.

With spandex (elastane), the problem runs the other way: too little goes in. The spec says "95% cotton, 5% spandex," but if only 2 to 3% is used, the fabric looks similar at first, then knees and necklines stay stretched out after a few wears.

The fibers you meet most often on the factory floor fall into seven groups.

A polyester blend is not a bad product in itself; performance fabrics blend it on purpose. The problem is using fibers that differ from the label, or lowering the share of expensive fibers and still selling it as "100% cotton" or "50% wool." Apparel imports in general are covered in Episode 67 and children's products in Episode 65. This article focuses on confirming that the garments you received are made with the fibers and ratios you were promised.

2. Verification Methods — From Hand Feel to Lab Analysis

Ask "Is the composition right?" and the factory will almost always answer "100%纯棉，没问题." Decide how you will check before you rely on words.

Use the burn test for screening only

The simplest method at inspection is to pull a few yarns from the fabric edge and burn them. Cotton and rayon smell like burning paper and leave soft gray ash. Polyester and nylon melt as they burn and form a hard bead at the end. Wool smells like burning hair and its ash crumbles easily between the fingers. If fabric sold as 100% cotton forms a hard bead, polyester is in it. It will not tell you the blend ratio, though, so when in doubt, move on to sealing samples and sending them to a lab.

Fabric weight takes one scale to measure

After composition, fabric weight is the next thing that changes easily. Cut a sample with a 113 mm diameter circular cutter (100 cm²), weigh it and multiply by 100 to get g/m². With a scale and cutter it takes a few minutes, and comparing with the approved sample shows right away whether the fabric got thinner. When reviews say the shirt feels thinner even though the composition is the same, this number has usually dropped.

3. What Are the Labeling Tolerances?

Fiber content labeling tolerances differ by country. In Korea, the household textile labeling standard requires the difference between labeled and actual content to stay within an allowed range, and China's GB/T 29862 generally allows ±5 percentage points. The US (16 CFR 303) and the EU (Regulation 1007/2011) are stricter at ±3 points. Labels saying "100%" or "纯" (pure) require almost no other fiber, so they are judged far more strictly than ordinary blends. Approximate values commonly used for quality control are below.

The values to watch most closely are the main fiber's content and fabric weight. Both tie directly to cost, so they are the first things a factory touches when meeting a price, and most problems found in Korean safety surveys and consumer group tests are fiber content labeling issues. Pilling and abrasion are covered in Episode 146, and fabric shrinkage and colorfastness in Episode 132.

4. Why You Should Not Take Fabric Reports and Labels at Face Value

Ask for proof of composition and the factory usually sends a test report obtained by the fabric mill. These documents have gaps.

5. Common Supplier Substitutions

Fabric makes up around half of a garment's cost, and 100% cotton and TC fabric differ a lot in price per kilogram. When price pressure comes, factories touch this part first. These are the types we have actually encountered in consultations.

The most common pattern is changing fabric on reorders. Factories are careful with the first batch because they are watching customer response, but from the reorder on they hand over the same report and switch the fabric. Requiring prior approval for material or process changes is covered in Episode 119, and the same principle of secret material swaps is explained for leather in Episode 153 and down fill in Episode 155.

6. The Damage Fiber Substitution Leaves Behind

Fiber content problems do not show at shipment; they surface only after customers wear and wash the garments a few times. The damage spreads well beyond the cost of the garments.

• Labeling violations: If a safety survey or consumer group test finds different fiber content, sales suspension, recalls and correction orders can follow, and the importer bears responsibility.
• Mass returns: A lot is cut from the same fabric, so if one shirt pills, the rest will too. Returns and refunds arrive all at once.
• Sales channel penalties: Large platforms delist products or lower seller ratings when reports of incorrect material labeling pile up.
• Brand trust: Basic tees and knits live on repeat purchases, so a single "this isn't 100% cotton" review drags down next season's sales too.

For recalls and product liability, see Episode 53, and for claims and disputes, Episode 36.

7. Items to Put in the Spec Sheet

A single line saying "100% cotton" gets interpreted differently at every factory. Put the items below in a table and attach it to your spec sheet.

Listing fabric by component is tedious, but necessary. If the body is 100% cotton but the neck rib contains spandex, the label has to reflect it, and swapping linings or pocketing to cheap polyester is common. For writing spec sheets and BOMs, see Episode 59.

8. How to Add Fiber Checks to Your QC Checklist

Sample stage

When you receive the approved sample, send one piece to a lab to measure composition, fabric weight and yarn count, and record them as your baseline. That record becomes the reference point for comparing production. Cut a small swatch of the approved fabric, write the date and article number on it and keep it; it makes later comparisons easy. Sample management is covered in Episode 34.

Production stage

When fabric arrives, get fabric roll label photos, lot numbers and the mill's test report. Before cutting, weighing swatches from a few rolls and burning a few yarns can be done on the spot. If photos of the cutting room show rolls with different labels mixed together, ask right there. For production tracking, see Episode 102.

Pre-shipment inspection stage

The inspector picks packed goods, weighs the fabric and screens with a burn test. If hand feel or weight differs a lot from the approved sample, or the burn result looks wrong, seal randomly selected samples and send them to a third-party lab for quantitative analysis. Pre-shipment inspection is covered in Episode 100 and third-party inspection in Episode 47.

9. Example Request Wording for the Factory

Putting the wording below in your purchase order or spec sheet takes fabric choice out of the factory's discretion and makes it easier to assign responsibility when a claim arises.

"本产品须使用指定面料商、指定型号的面料，成分为100%精梳棉（按GB/T 2910或ISO 1833方法检测），纱支为20支精梳纱，克重为180g/㎡，允许偏差±5%。严禁掺入涤纶或任何未标示的纤维，不得以普梳纱或其他面料替代。未经我方书面同意，不得更换面料商、面料型号或生产工厂。每批须提交面料批号、面料卷标签照片、面料商检测报告及裁剪记录；如标示再生或有机成分，须提供对应批次的交易证书（TC）。检测样品由我方验货员从成品中随机抽取并封样。如有争议，以第三方实验室的检测结果为准。如有不合格，须加抽复检；复检仍不合格的批次暂停出货，并更正标签或使用合格面料重新生产。"
(This product must use fabric of the designated article from the designated fabric mill, with a composition of 100% combed cotton (tested by GB/T 2910 or ISO 1833), 20s combed yarn and a fabric weight of 180 g/m², with a tolerance of ±5%. Polyester or any unlabeled fiber must not be blended in, and carded yarn or other fabric must not be substituted. The fabric mill, fabric article or production factory must not be changed without our written consent. Each lot must come with the fabric lot number, fabric roll label photos, the mill's test report and cutting records; if recycled or organic content is claimed, the transaction certificate (TC) for that lot must be provided. Test samples are drawn at random from finished goods and sealed by our inspector. In case of dispute, the third-party lab result prevails. If a failure occurs, additional samples are drawn for retesting; lots that still fail are held from shipment, and labels are corrected or the goods are reproduced with conforming fabric.)

10. Three Real Cases

These are anonymized versions of patterns we often encounter in consultations. Amounts and figures are examples.

Case 1 — 100% cotton short-sleeve tees

This is the case from the opening. When the brand confronted the factory with the test results, the factory held out: "The mill's report says 100% cotton." But fabric roll label photos showed the same mill's CVC article mixed in, and there were no cutting records at all. The weak point was a spec sheet that said only "100% cotton," without a fabric article, weight or test method. Returns, label corrections and inventory discounts added up to a loss of about KRW 48 million, and the factory covered only part of the fabric price difference. Now the brand writes the fabric article and weight into the spec sheet and weighs fabric at every receipt.

Case 2 — 50% wool knit

A womenswear brand sold 2,000 knits labeled "50% wool, 30% nylon, 20% acrylic," and inquiries kept coming: "It's supposed to be wool, but the static is terrible and it pills everywhere." The only document from the factory was the yarn supplier's composition sheet. A lab found 21% wool and 49% acrylic. Since then, the brand seals finished garments from every lot for quantitative analysis and has fixed the yarn supplier and yarn article in the spec sheet.

Case 3 — Linen shirts

A menswear brand sold 1,200 shirts labeled "100% linen," and some reviews said "it shrinks and goes limp when wet." Testing showed 55% linen with the rest rayon. On the surface, the fabric even mimicked linen's characteristic slubs. Since then, the brand gets a fiber identification test for the first batch and every reorder, and matches lot numbers on fabric roll labels and test reports.

11. Common Mistakes

• Passing goods based only on "100% cotton" on the label and the mill's test report
• Assuming the reorder would match because the first batch was fine
• Specifying composition but not fabric weight or yarn count
• Checking only the body fabric and not rib, lining or pocketing
• Mistaking a copy of a GRS or GOTS certificate for proof covering that order
• Not checking that tolerances differ by destination country

12. Fiber Content Control Checklist

Specification stage

• Fiber type, content and test method are defined
• Yarn count and fabric weight are written as numbers
• Fabric mill and fabric article are fixed
• Unlabeled fibers and undeclared recycled fiber are prohibited in writing
• Fabric and composition are listed by component: body, rib, lining
• Labeling standards and tolerances for the destination country are confirmed

Sample and production stage

• Composition, weight and yarn count of the approved sample were tested as a baseline
• A swatch of the approved fabric is kept with date and article number
• Fabric lot numbers and fabric roll label photos were received
• Fabric was weighed and burn-tested at receipt
• If claiming recycled or organic, a transaction certificate (TC) was received

Pre-shipment inspection stage

• Fabric weight of randomly selected finished goods was measured
• Unlabeled fibers were screened with a burn test
• Samples were sealed and sent to a lab for quantitative analysis
• Reorders were checked against the same criteria as the first batch

Wrapping Up - Check Test Results, Not the Label

T-shirts leaving the factory look equally soft and clean whether they are 100% or 65% cotton. Pilling and stretched necklines only become visible after customers wear and wash them a few times. Writing the fabric article, weight and test method into the spec sheet and sending a few finished garments per lot to a lab does not cost much. Put a few hundred thousand won in lab fees next to tens of millions in returns and inventory discounts, and it is clear which is cheaper.

There is also something you can do right now. Ask the factory currently in production to send the mill name and article number of the fabric in use, the fabric lot number, and fabric roll label photos. If the answer is a single line saying "都是按要求做的 (everything was made as required)," draw up a fiber control conditions table and send it before your next order.

StartMade supports you on the ground with spec sheets that include fabric articles and content and weight criteria, recording approved sample composition, checking fabric receipt and cutting records during production, and pre-shipment inspections that seal samples for lab testing. If you have already received fiber content or pilling claims, we can start with testing remaining stock; if you are preparing a new season, we can start with fabric and factory selection.