# How do hair straighteners work? Source: https://plateandcurl.co.uk/blog/how-do-hair-straighteners-work Published: 2026-10-11 Publisher: Plate and Curl **In short:** Hair straighteners heat two plates and press hair between them. The heat temporarily breaks the weak hydrogen bonds that hold hair's natural shape, and the pressure and tension hold it straight while it cools and the bonds re-form. Sensors keep the plates at a set temperature. Steam and infrared models add moisture or specific heat claims to the same basic method. A straightener looks simple: two hot plates on a hinge. But what happens to your hair, and why premium stylers cost far more than basic ones, comes down to how the heat is produced and controlled. This guide explains the science in plain terms, the parts inside a modern straightener, and what marketing terms such as infrared, ionic and steam actually describe. It should help you read a listing with a clearer idea of what matters. ## What heat does to hair Hair's shape is held by two kinds of bonds inside the strand. Strong disulphide bonds set your natural curl pattern and are only changed by chemical treatments such as perms or relaxers. Weaker hydrogen bonds also help hold the shape, and these break with heat and water. When you pass hair through hot plates, the heat breaks those hydrogen bonds and the tension pulls the strand straight. As the hair cools, the bonds re-form in the new straight position. This is why straightened hair stays straight until it meets moisture, such as rain, steam or sweat, which lets the bonds break and re-form in the natural shape again. ## Inside a modern straightener - **Plates:** usually ceramic or titanium, often coated for a smooth glide. See [ceramic vs titanium plates](https://plateandcurl.co.uk/blog/ceramic-vs-titanium-plates). - **Floating mounts:** springs behind the plates keep even pressure as hair passes through. - **Heaters:** usually ceramic heating elements bonded behind each plate. - **Temperature sensors:** measure plate heat so the control board can hold it steady. - **Insulated shell:** keeps the outer body cooler to hold. - **Swivel cord and safety features:** sleep mode and auto shut-off on most premium models. ## Why sensors matter A cheap straightener may heat up to a temperature and then drift as hair draws heat away. A thick section cools the plate, so the next section gets less heat, and you end up doing extra passes. Premium stylers use sensors that check temperature many times a second and adjust. ghd's dual-zone and ultra-zone technology are examples. ghd describes the Gold as having a sensor across each plate, and the Platinum+ and Chronos as using predictive or motion-responsive sensing, all to hold 185 °C (365 °F). The aim is consistent heat so one pass does the job. Read more in [what temperature should straighteners be](https://plateandcurl.co.uk/blog/what-temperature-for-straighteners). ## Infrared and ionic claims Every hot object gives off infrared radiation, so in a sense every straightener is infrared. Brands that market infrared straighteners usually mean that their plates or coatings are designed to emit more of their heat in this form, which they say heats hair more gently from within. Treat it as a description of the plate design rather than a different way of straightening. Ionic claims refer to the release of negatively charged ions, which brands say reduce static and frizz. The effect on the finished style is hard to measure at home. Plate quality, temperature control and technique make a bigger, more obvious difference. ## Hair straighteners with steam Steam straighteners, such as L'Oréal Professionnel's SteamPod, have a small water tank. They release steam onto the hair as the plates pass. The idea is that moisture helps the hair stay supple while heat styles it. The hair is still straightened by heat and tension on dry hair; the steam is an addition, not a replacement for the plates. Steam models need filling, are bulkier and need occasional descaling, especially in hard water areas. They suit people who like the finish and do not mind the extra steps. ## Hot air instead of plates A newer category skips the plates altogether. The Dyson Airstrait, ghd Duet Style and Shark SilkiPro use jets of heated air directed between two arms to dry and straighten hair from wet. The principle is the same, bonds re-forming as hair cools under tension, but the heat comes from air. See [can you use straighteners on wet hair](https://plateandcurl.co.uk/blog/can-you-use-straighteners-on-wet-hair) and our [best wet-to-dry straighteners](https://plateandcurl.co.uk/best/best-wet-to-dry-straighteners) guide. [Compare premium straighteners](https://plateandcurl.co.uk/best/best-hair-straighteners) ## Frequently asked questions **Do infrared straighteners work differently?** Not fundamentally. They still heat and press hair. Infrared refers to how the plate is designed to give off heat. **Are steam straighteners better for hair?** They add moisture during styling, which some people prefer. They still use heat, so heat protection matters. **Why does straightened hair go curly in the rain?** Moisture lets the hydrogen bonds break and re-form in your natural shape. **Why are premium straighteners more expensive?** Mostly better temperature control, plate quality, build and guarantees, rather than a different way of straightening. ## Buying guides on this topic - https://plateandcurl.co.uk/best/best-hair-straighteners - https://plateandcurl.co.uk/best/best-wet-to-dry-straighteners - https://plateandcurl.co.uk/best/ghd-straighteners-compared ## Sources - [ghd support](https://www.ghdhair.com/uk)