When human hair lacks enough natural moisture, or when it’s exposed to high or low humidity, it may become brittle and/or rough. To this end, hair straighteners, or flat irons, can be used as a quick and easy way to make frizzy and curly hair temporarily straight.
Curly hair is often caused by positively charged hydrogen bonds between the keratin proteins. Flat irons use intense heat to break these bonds. This heat is transferred to the aluminium and ceramic plates of the straighteners – between which the hair is clamped -before stroking downwards. A negative charge is also often run through the irons, which aids in breaking the bonds.
The curlier the hair, the more heat will be required to straighten it as more bonds are present. Too much heat, though, can burn and damage the hair, so these devices must always be used with care.
Flat irons up close
What’s going on inside this popular hair-styling gizmo?
Hinge – A spring-loaded hinge enables the two parts of the straighteners to be brought together in the user’s hand.
Element – Heating elements within the device are thermostatically controlled to direct the required heat into the plates.
Protection – A thin material that is a good insulator, like plastic, is used at the edges of the plates to prevent the scalp from being burned.
Plate – Lightweight aluminium in the plates allows for rapid heat transfer, while ceramic prevents hair sticking to them.