How to

How to spec cotton in your brief — fabric weight, yarn and tolerances without ambiguity

A guide to writing a cotton technical brief your supplier understands on the first read: fabric weight, yarn, weave, finish, certifications and tolerances. What must be in writing before you request the strike-off.

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Why cotton cannot be ordered as "one that feels nice"

Ordering a cotton tee, hoodie or tote that "feels nice" is the surest recipe for inconsistent product. Cotton varies enormously by origin, yarn, weave and finish. A 145 g/m² combed ring-spun tee is not the same as a 145 g/m² open-end tee; a 320 g/m² three-end French-terry hoodie is not the same as a 280 g/m² single-loop fleece. The word "cotton" covers dozens of products.

The technical brief is the document that closes that ambiguity. It is the difference between receiving 1,000 tees and discovering on the third wash that they shrank 8%, that the logo color bled or that the hand-feel is not what you remembered from the sample. The brief is not optional — it is the artifact that carries the entire conversation with the supplier.

What the brief must close: fiber composition (100% cotton vs blend with recycled polyester), yarn type (ring-spun, open-end, compact), fabric weight in g/m² with tolerance (not "180 g/m²" but "180 g/m² ±5%"), weave type (jersey, piqué, 1X1 rib, fleece), finish (pre-shrunk, softened, mercerized, sanforized), applicable certifications (OEKO-TEX Standard 100, GOTS, Fairtrade, Better Cotton) and shrinkage tolerances (3% max after 5 washes per ISO 6330).

For programs in Mexico, two additional considerations: NOM-050 requires fiber composition labels in Spanish, with care symbols per ISO 3758. And if the product crosses to Europe, REACH SVHC and Regulation (EU) 1007/2011 on textile fiber labeling apply to exported merch. The brief must anticipate both when the program crosses a border.

Seven steps to write the cotton technical brief

  1. Define fiber composition and origin: 100% cotton vs blend (80/20, 70/30 with GRS-recycled polyester when applicable); cotton type (Upland, Pima, Supima, Egyptian, GOTS-organic); country of origin if critical (Peruvian Pima, Indian, US, Mexican).
  2. Specify the yarn: ring-spun, open-end, compact or double ring-spun. Ring-spun gives finer hand-feel and better print; open-end is cheaper and rougher. If the program is premium uniforms, ring-spun or compact; if mass merch, open-end can work.
  3. Set fabric weight and tolerance: 145 g/m² for a lightweight tee, 180 g/m² for a standard tee, 200 g/m² for a premium tee, 280 g/m² for a mid-weight hoodie, 320 g/m² for a heavy hoodie. Tolerance ±5% in production; ±8% on individual pieces for normal variation.
  4. Detail weave and construction: single jersey, piqué (for polo), 1X1 rib (collar and cuffs), three-end loop-back fleece (sweatshirt), brushed-back fleece (light hoodie lining). Stitch count per cm if you have an internal standard.
  5. Finish and pre-shrink: pre-shrunk by sanforizing or compact washing; residual shrinkage max 3% after 5 washes per ISO 6330. Mechanical or chemical softening; mercerize if you want more luster and better ink uptake.
  6. Certifications and claims: OEKO-TEX Standard 100 (free of restricted substances); GOTS for organic; Fairtrade or Better Cotton for social responsibility; GRS for recycled content when applicable. Claims must fit on the label per LFPDPPP and NOM-050.
  7. Tolerances and measurement method: fabric weight per ASTM D3776; shrinkage per ISO 6330; wash color fastness per ISO 105-C06; tensile strength per ASTM D5034. Each metric with its standard, target and tolerance.

Common mistakes when specifying cotton

The first mistake is not putting a tolerance on the fabric weight. If you ask for "180 g/m²" without tolerance, the supplier can deliver 171 g/m² (5% under) and argue they "approximately" comply. Always specify ±5% in production and verify with a physical sample, not with the supplier's word.

The second mistake is confusing combed ring-spun with carded ring-spun. Combed is finer, more even and better for print; carded has more short fibers, is rougher and the print looks less defined. For logos with fine detail or small text, combed always.

The third mistake is forgetting the pre-shrink. A non-pre-shrunk tee shrinks 5% to 8% in the first two washes. An XL can end up as an L. Ask for pre-shrink by mechanical compacting or sanforizing and verify with a wash test per ISO 6330.

The fourth mistake is not specifying color fastness. You ask for "black cotton" and get cotton dyed with low-fastness pigments. After five washes the black turns greenish gray. Ask for wash color fastness ≥ 4 per ISO 105-C06 and archive the lab report.

The fifth mistake is mixing incompatible certifications. A product cannot be GOTS and Better Cotton at the same time; it can be GOTS or Fairtrade. The brief must say which applies and which claims you can use on the label and in advertising per LFPDPPP.

The sixth mistake is not considering freight between facilities when merch crosses borders. Under USMCA/T-MEC, rules of origin apply when there is an origin claim. NOM-035 also applies if merch is manufactured in shared centers. These points must be in the brief from the start, not halfway through the program.

Tools, templates and references

Downloadable technical brief: at the end of this guide we include a template with the brief fields (composition, yarn, fabric weight, weave, finish, certifications, tolerances, test methods) ready to adapt to each product in your program.

Recommended equipment: digital caliper, 0.1 g precision scale, metal ruler, D50 light lamp (5,000 K) to evaluate color, 10× loupe to inspect weave, and Pantone chips for color. For wash tests, a standard washer and the ISO 6330 method documented.

Technical and legal references: NOM-050 for textile labeling in Mexico; ISO 3758 for care symbols; ISO 6330 for domestic washing; ISO 105-C06 for color fastness; ASTM D3776 for fabric weight; ASTM D5034 for tensile strength; OEKO-TEX Standard 100; GOTS; GRS; LFPDPPP for claims; REACH SVHC and Regulation (EU) 1007/2011 for exports to Europe.

Suggested cadence: signed technical brief before each new product or supplier change; physical strike-off verification against the brief before releasing production; archive of lab reports per batch; annual review of supplier certifications.

Real numbers for a 180 g/m² tee brief: target 180 g/m², tolerance ±5% (171 to 189 g/m² acceptable); yarn ring-spun combed; weave single jersey 28 stitches per 7 cm; finish pre-shrunk sanforized, residual shrinkage ≤ 3% after 5 washes ISO 6330; color fastness to wash ≥ 4 per ISO 105-C06; tensile strength ≥ 220 N warp and ≥ 150 N weft per ASTM D5034. Anything outside the brief fails the strike-off.

Quick field test on the strike-off: cut a 10 × 10 cm square, weigh it on a 0.1 g scale (target 1.80 g at 180 g/m²), stretch it 10% and look for yarn slippage, rub it 20 times against a white cotton cloth and rate pilling, soak it in water for 5 minutes and check for dye bleeding. These five tests take 15 minutes and catch 80% of the most common brief mismatches before production.