Workwear Fabrics Explained: Polyester, Cotton, GSM and How to Wash Them
What the fabric label on your workwear means: poly-cotton blends, GSM weight, ripstop and Cordura® reinforcement, EN standards and the washing rules that keep hi-vis and FR clothing compliant.
Two pairs of work trousers can look identical on the shelf and behave completely differently on site. The difference is printed on the label: fibre mix, fabric weight, weave and the standards the garment is certified to. Here's what each part means and how to use it when you buy.
- Polyester-rich blends like
65/35keep their shape and colour through heavy washing. That's why they're the workwear standard. -
GSMis fabric weight: around 240 g/m² for service work, 300 g/m² for trades. - Reinforced knees and seams matter more than a few extra grams.
- For flame and welding, buy certified FR clothing. Standard polyester blends can melt.
- No fabric softener and no bleach on hi-vis, FR or antistatic clothing.
The fibres, and where each one belongs
In fashion, cotton is the default and polyester is the compromise. In workwear it's the other way round.
The industry standard
Polyester holds the shape, colour and size through heavy washing. Cotton makes it comfortable to wear all day.
Reinforcement (Cordura®)
Used where trousers wear out first: knees, hems, back pockets and ruler pockets.
Stretch
Usually a few percent, in panels at the crotch, knees and back. It's there so you can move, not for the look.
Base layers
Polypropylene and merino move sweat away from the skin. A cotton layer underneath holds it and leaves you cold.
Examples in the shop: 65/35 twill, polypropylene and merino
Flame and welding: certified fabric, not just cotton
Polyester melts at around 250 °C and can stick to the skin in a flash fire or an arc. That's why standard poly-cotton workwear doesn't belong near welding or open flame. The answer isn't simply "wear cotton", though. Untreated cotton burns too. What protects you is clothing tested and certified to EN ISO 11611 (welding) or EN ISO 11612 (heat and flame).
Certified FR clothing is often cotton-rich, but not always 100% cotton. The Sir Safety Polytech trousers below are 75% cotton and 24% polyester and carry EN ISO 11611, 11612 and arc flash certification. The fabric is treated and tested as a whole.
Certified flame-retardant examples
GSM: the number most buyers ignore
GSM (g/m²) is the weight of the fabric per square metre. It tells you more about how a garment will wear than the brand name does.
- 135Knitted performance T-shirts. Light and quick-drying.
- 240Industry and service trousers. Flexible, good in warm weather.
- 300The craftsman standard: tools, kneeling, construction.
- 310+Heavy-duty work and cold stores.
Examples at 135, 245 and 300 g/m²
Weave and reinforcement beat weight alone
The standard weave
Diagonal ribs make a dense, hard-wearing fabric. Most work trousers use it.
A weave, not a fibre
Reinforcing yarns every few millimetres stop a small tear from spreading. A lighter ripstop can outlast a heavier plain fabric.
A 300 g/m² trouser with unprotected knees will fail before a 240 g/m² trouser with Cordura® knee pockets and triple-stitched seams. Look at the knees, pockets and hems, not just the headline weight.
Ripstop and Cordura® reinforced examples
What the label is really telling you
On workwear, the label is a compliance document. The standards you'll see most often:
| Standard | What it covers |
|---|---|
| EN ISO 20471 | High visibility, class 1 to 3 by the amount of fluorescent and reflective material |
| EN ISO 11612 | Protection against heat and flame |
| EN ISO 11611 | Welding |
| EN 1149-5 | Antistatic |
| EN 343 | Rain |
| EN 13034 | Limited splashes of liquid chemicals |
| EN 14404 | Knee protection, valid only with the matching knee pads fitted |
| EN ISO 15797 | Suitable for industrial laundering |
| OEKO-TEX® 100 | Tested for harmful substances |
Every class and letter behind these codes is explained in our guide to EN codes on workwear and PPE.
Washing: where workwear rules differ
- Never use fabric softener. It leaves a film that dulls reflective tape, blocks moisture wicking and can reduce flame-retardant and antistatic performance.
- Never bleach. It attacks reflective bands and weakens FR treatments.
- Wash hi-vis separately, or only with other hi-vis. Dye from dark workwear can move onto the fluorescent fabric and bring it below its class.
- Follow the label, not habit. Temperatures vary a lot. The Blåkläder 15841860 hi-vis twill trouser can be washed at 60 °C, while the Helly Hansen LIFA base layer is limited to 40 °C with no tumble drying.
The number under the wash tub symbol is the maximum number of wash cycles for which the colour and reflective tape stay certified, often 25 to 50. The Sir Safety Mistral trousers below are certified for 50. Past that number the garment no longer complies. Replace it earlier if the tape is cracked, peeling or permanently dull.
Hi-vis trousers and their care labels
Quick pick by trade
| Work | Fabric to look for |
|---|---|
| Construction, carpentry, roofing | 300 g/m² poly-cotton twill, Cordura® knees, knee pad pockets |
| Industry, service, logistics | 240 g/m² twill with stretch panels |
| Welding, foundry, arc flash | Clothing certified to EN ISO 11611 / 11612, never standard poly-cotton |
| Roadworks, rail, warehouse traffic | EN ISO 20471 class 2 or 3, wash count checked |
| Outdoor and winter | Polyester ripstop shell with a membrane, over a merino or polypropylene base layer |
| Hot weather | Knitted polyester T-shirt around 135 g/m², not a cotton tee |
Quick answers
What is the best fabric for work trousers?
For trades work, a 65% polyester / 35% cotton twill at around 300 g/m² with Cordura® reinforcement is the best all-round choice. For lighter industrial and service work, a similar blend at around 240 g/m² with stretch panels is more comfortable.
What does GSM mean on workwear?
GSM is grams per square metre, the weight of the fabric. Around 240 g/m² is light industrial workwear, 300 g/m² is the standard for construction and trades, and 310 g/m² or more is heavy duty.
Can I use fabric softener on work clothes?
No. Fabric softener leaves a residue that reduces the reflectivity of hi-vis tape, blocks moisture wicking and can reduce flame-retardant and antistatic protection. Use detergent only.
How many times can hi-vis clothing be washed?
Each EN ISO 20471 garment shows a maximum wash count on its label, often 25 to 50 cycles. After that the fluorescent colour and reflective tape are no longer certified and the garment should be replaced.
Is polyester safe for welding or electrical work?
Standard polyester workwear is not. Polyester melts at around 250 °C and can stick to the skin. For welding and arc flash risks, wear clothing certified to EN ISO 11611, EN ISO 11612 or IEC 61482-2. Plain untreated cotton isn't certified protection either.
Where can I buy certified workwear in Europe?
Bitco Workwear supplies certified workwear and PPE from Sir Safety, Helly Hansen, Blåkläder, Kübler, Planam, S.24 and TMG, and ships across the EU. Fabric composition, weight and EN certification are listed on the product pages.
Filter by fabric and standard
Every collection lets you narrow down by material and EN standard, so you can go straight to poly-cotton trousers, merino base layers or the FR range. The weight is listed on each product page.
