Iron Temperature by Fabric: Reading the Dot System
Iron temperature is the fastest way to ruin a garment in ten seconds — too hot and you scorch or melt the fiber, too cool and you're pressing water into wrinkles that won't budge. The dot symbols on a care label exist to solve this, but the two organizations behind the international standard don't quite agree on the exact degrees each dot means, and iron manufacturers sometimes recommend something different still. Here's how to read the dots, where the numbers diverge, and which fabrics need the practical exception.
Key takeaways
- Dot temperatures differ by authority: ISO lists 110/150/200°C, GINETEX lists 120/160/210°C max sole-plate — stay toward the lower number on delicates.
- Always iron by the care label's dot count, not by what you assume the fiber needs.
- Silk is officially 2-dot/medium but scorches at that temperature in practice — iron it low, dry, inside out, with a press cloth.
- Polyester is a medium-heat (2-dot) fabric, not a low-heat one.
- Iron coolest to hottest: synthetics/silk, then wool, then cotton, then linen.
What the Dots Mean — and Where the Standards Disagree
Care labels use one, two, or three dots to signal iron temperature, low to high. The catch: the ISO reference figures and GINETEX (the organization that administers the international care-symbol system) publish different degree values for the same dots. ISO lists 110°C / 150°C / 200°C for one, two, and three dots; GINETEX's own published maximum sole-plate temperatures are 120°C / 160°C / 210°C. The gap is roughly 10°C at every level. Either reading keeps you safe if you stay toward the lower of the two on delicate fabrics — on iron-safe fabrics like cotton and linen the difference doesn't matter in practice.
The rule that matters more than either number: GINETEX specifies that you select iron temperature by what the care label says, not by what you assume the fiber content should need.
Fabric-by-Fabric Iron Temperature
| Fabric | ISO dot temp | GINETEX max sole-plate | Iron-maker reference (Rowenta) | Steam |
|---|---|---|---|---|
| Nylon / synthetics | 110°C (1 dot) | 120°C | ~110°C, low | None |
| Acetate | 110°C (1 dot) | 120°C | — | None |
| Silk ⚠️ | 150°C (2 dots) | 160°C | ~110°C, low in practice | Low or none |
| Wool | 150°C (2 dots) | 160°C | ~150°C (300°F), medium | Light |
| Polyester ⚠️ | 150°C (2 dots) | 160°C | ~135–150°C (250–300°F), medium | Light |
| Rayon / viscose | 150°C (2 dots) | 160°C | ~135–150°C (250–300°F), medium | Light |
| Cotton | 200°C (3 dots) | 210°C | ~175–205°C (350–400°F), high | Yes |
| Linen | 200°C (3 dots) | 210°C | ~175–205°C (350–400°F), high | Strong |
The Silk Exception
Silk is where the standard chart and real-world practice split hardest. The official dot standard files silk at two dots — the same "medium," 150–160°C setting as wool and polyester. Iron manufacturers know better: Rowenta and other iron makers effectively treat silk as a low-heat fabric in practice, closer to 110°C, because silk scorches, yellows, and water-spots far more easily than the standard chart implies. The practical approach: iron silk on LOW, fully dry (not damp — water on silk leaves marks), inside out, and with a press cloth between the iron and the fabric.
Polyester Needs Medium — Not Low
A common mistake is treating every synthetic the same way. Polyester is a two-dot, MEDIUM-heat fabric under both ISO and GINETEX — not the lowest setting. Iron it too cool and the wrinkles won't release; iron it too hot and it turns shiny or melts at the seams. Save the lowest setting for the fabrics that actually call for it: nylon, acetate, and other truly heat-sensitive synthetics.
Ironing Order, Steam, and Technique
If you're ironing a pile of mixed fabrics, work coolest to hottest: synthetics and silk first, then wool, then cotton, then linen last. An iron heats up faster than it cools down, so starting cool and working up avoids scorching something delicate with residual heat from the last item.
Use steam on cotton, linen, denim, and wool blends — the moisture helps relax thicker fibers. Skip steam on synthetics (low heat), silk, and dark fabrics, where steam can leave water spots or shine. Iron silk, satin, wool, velvet, lace, and synthetics inside out, and use a press cloth for anything delicate or embellished. For velvet, don't drag the iron across the pile at all — press pile-side down over a towel, or hold a steam iron an inch or two above the fabric and let the steam do the work.
For water: tap water is fine for most modern irons; if yours is very hard, cut it 50:50 with distilled water. Empty the reservoir before you put the iron away.