Butter-soft vs brushed polyester: how to spec yoga fabric

“Butter-soft” and “brushed polyester” are marketing words, not specifications. Here is how to turn them into numbers you can put in a purchase order.

Fabric is 35–45% of the FOB price of a yoga garment and almost all of the customer’s first impression. Getting the specification right before sampling saves more money than any negotiation later.

The three numbers that matter

Composition

Nylon-spandex and polyester-spandex behave differently, and the difference is visible on the body.

  • Nylon-spandex (typically 75/25 or 80/20) — softer hand-feel, better drape, cooler touch, deeper colour. It is what most premium leggings use. It costs more and is slightly less resistant to chlorine.
  • Polyester-spandex (typically 78/22 or 82.5/17.5) — more compressive, holds shape well, dries faster, cheaper. Brushed on the inside it feels close to nylon at a lower price.

Weight (gsm)

Grams per square metre decides opacity and how the garment hangs. For leggings:

WeightBest forNotes
180–200 gsmSports bras, tops, summer shortsLight, breathable; too thin for a squat-proof legging
220–240 gsmLeggings, bodysuitsThe mainstream range; opacity depends on knit, not just weight
250–280 gsmHigh-compression leggings, winterHolds shape, feels substantial, warmer
300+ gsmFleece-lined, outerwearBulky for studio wear; check stretch recovery

Stretch and recovery

Ask for two numbers: stretch percentage (how far it extends before resistance) and recovery (how much it returns). Good leggings fabric extends 120–160% and recovers to within 3–5% of original width after five washes. A fabric that extends well but recovers poorly looks baggy at the knee by week three.

Butter-soft, brushed, and what the words hide

Butter-soft usually means a fine-gauge interlock with a peach finish — sanded lightly on the face so it feels smooth and slightly matte. It shows fewer deep colours than a shiny knit and photographs well, which is why brands like it.

Brushed means the inside has been mechanically raised, creating a soft, warm hand-feel. It is excellent for autumn/winter and for comfort-led lines, but it pills faster at friction points if the yarn is short-staple. Ask for a pilling result (Martindale or ICI) — 4 or above is what you want.

Neither term has a legal definition. A purchase order that says “butter-soft” is unenforceable; one that says “75/25 nylon-spandex, 230 gsm ±5%, peach finish, pilling ≥ 4, recovery ≤ 5% after 5 washes” is.

The squat test, properly

Opacity is the single most common return reason on leggings, and it is predictable before bulk. Do this on the actual production fabric, not a photo:

  1. Cut a 30 × 30 cm square.
  2. Stretch it over a knee or a rolled towel to roughly the tension it will see in a deep squat.
  3. Put a bright light behind it and look from the front.
  4. Repeat with the darkest colour you plan to sell — dark colours hide more, light colours reveal more.

If you can read text through it, the fabric is too light, the knit too open, or the colour too pale. Fix it in the specification, not in the marketing copy.

Colour fastness

Ask for results on three tests, because they fail differently:

  • Wash fastness — colour loss after repeated washing; a 4 or above is normal for activewear.
  • Rubbing (crocking) — dry and wet. Wet crocking is where dark navy and black fail, and it is what stains a light-coloured yoga mat.
  • Light fastness — matters if the garment will be worn outdoors or displayed in a shop window.

What to put in the tech pack

ParameterExample
Composition75% nylon / 25% elastane
Weight230 gsm ±5%
FinishPeach (butter-soft), both sides
Stretch / recovery≥ 130% stretch; ≤ 5% growth after 5 washes
OpacityNo show-through at 150% stretch, darkest and lightest colour
Pilling≥ 4 (Martindale, 4 h)
Colour fastnessWash ≥ 4, wet crock ≥ 3–4
CertificationOEKO-TEX Standard 100, class II

Certification, briefly

OEKO-TEX Standard 100 is issued to the fabric and the mill, not to the brand or the trading company. Ask for the certificate number and check the article list covers the fabric weight and colour range you are buying. If a supplier cannot produce a number, treat “OEKO-TEX certified” as a claim, not a fact.

How to sample fabric cheaply

Ask for a swatch card: 20 × 20 cm of each candidate fabric, labelled with composition, weight and finish. It costs a courier envelope, and it lets you wash, stretch and photograph all three options side by side before you commit to a sample garment. Most mills will send one against a courier account.

Once the fabric is fixed, the rest of the project — pattern, sampling, bulk — becomes a scheduling exercise rather than a negotiation.

See the fabrics we hold or ask for a swatch card for the three weights you are considering.