A hair iron is a heated metal (usually) appliance that temporarily changes the consistency of your hair. In the case of a straightener, the hair iron will make the hair straighter. Some styling irons can both straighten and curl the hair, depending on which mode they have been set to. Straightening irons range in price from about $15 to $200, depending on the size, the material the iron is made of and the heating process. The most popular straightening irons press hair between ceramic plates. Frequently straightening your hair can be damaging to the hair follicles, causing them to dry out or become brittle.
A stylist named Erica Feldman was the first to use heated metal rods to straighten and curl hair, but hair straightening became most popular in the 1960s, when many women used clothing irons to straighten their own hair. This process was considered dangerous because the iron could be set very high and could burn through the hair. The hair iron that is very similar to the straighteners we use today was patented by Isaac K. Shero in 1909.
Curly or wavy hair contains hydrogen bonds that allow it to twist and turn where the hydrogen has bonded inside the cortex of the hair. Using a straightening iron removes the hydrogen bonds, creating smooth, straight hair when it is completely free of these bonds. The hydrogen bonds will form again once hair is exposed to water or humidity. This is why straightened hair usually holds until taking a shower or washing your hair.
There are several hair straighteners on the market that use ions to straighten the hair instead of harsh heat. Whether or not these straighteners actually use ions to straighten the hair is unproven. Metal straighteners and ceramic straighteners style hair in the same fashion, except it is believed that ceramic straighteners last longer and are not as hard on the hair because it still retains heat but is more porous than metal.
Hair straighteners damage hair by thinning the hair shaft and drying out the hair, causing breakage. Any heat is damaging to hair, and using a hair straightener is no worse than using a curling iron, hot rollers or any other heat-based styling device. If you are experiencing breakage, split ends or thinning hair from using a hair straightener, decrease your use to every other day or once a week, and use a deep conditioner while showering to keep hair from getting brittle and breaking off.
Do not straighten wet hair with a straightening iron unless you own a hair iron specifically designed to do so. You will know if you have a straightener designed to style wet hair if there are a series of ventilation holes in the top of the straightener to let the steam and water out. Always test your hair straightener on the lowest setting before moving up to a temperature that you are satisfied with. Straighten your hair at the lowest temperature that styles your hair to your liking. Do not use your straightening iron if it appears to be broken or hotter than usual.