Using heat styling tools with less stress on your hair

Heat styling does the most harm when any of three things happens: the hair is still wet, the tool runs hotter than the hair needs, or the same strands are passed over again and again. Each of these is within your control, and changing one habit often helps more than buying a new tool.

Heat works by temporarily loosening the hydrogen bonds in the hair's structure, which is how a curl or a straight shape holds its form. Damage builds when the hair is too hot for its condition, is heated while wet, or is passed over many times. Most of the difference comes from a short list of habits: dry hair, a sensible starting setting, a protectant applied before heat and a steady, limited technique. These habits apply to flat irons, curling irons and hot brushes alike.

Start with fully dry hair

Wet hair is more fragile than dry hair, and it swells as it takes up water, so the same tool can do more damage to it. Before you use a flat iron or curling iron, dry the hair completely, or as close to completely as you can get it. Blot the hair with a towel rather than rubbing it, because rubbing roughens the outer layer of each strand and creates frizz that is harder to smooth later.

If you blow-dry, use the towel to remove surplus water first, then work with the dryer on a medium setting. Keep the dryer moving so no single spot stays hot, and use a concentrator nozzle so the airflow follows the direction the hair lies. Finish each section with a cool setting if your dryer has one, which helps the style hold once the hair cools.

Choose a temperature that matches your hair

Many styling tools can go past 400°F (about 200°C), which is more heat than fine, bleached or previously colored hair needs for everyday styling. Start with the lowest setting that gives the result you want, then raise it only if the hair does not change shape. Check the manual for the tool's range, because the numbers on the dial do not mean the same thing across brands. A higher setting does not guarantee a longer-lasting style, and each step up adds stress to the hair.

A practical way to find the right setting is to test one small section first, beginning from these commonly cited starting points in Fahrenheit:

• Fine hair, or hair that is damaged: around 300°F or lower.
• Typical hair: roughly 300°F to 375°F.
• Coarse or very resistant hair: up to about 400°F, applied to dry hair in small sections.

Treat these numbers as starting points rather than targets, and start low if you are unsure. Once a test section works, keep that setting for the rest of the hair and repeat the test only when the condition of the hair changes. Hair that has been bleached or colored recently is more fragile than hair that has not been chemically processed, so stay at the lower end of the range during that period.

Apply a heat protectant before heat

Heat protectants are applied before heat, and the timing depends on the tool. Use them on damp hair before blow-drying, and on dry hair before a flat iron or curling iron. Many contain silicones or other film-forming ingredients that leave a thin layer on the hair. Spread a small amount through the mid-lengths and ends with a wide-tooth comb, since those areas are the oldest and the most prone to dryness. Follow the label for how much to use, because too much product can weigh fine hair down and leave it limp.

Protectants do not make heat safe at any setting. They work best alongside a lower temperature and fewer passes, and the label is the final word on whether a product is meant for damp or dry hair.

Limit passes and let styles set

Each pass with a styling tool adds heat exposure to the same strands. For most styles, one or two passes over a section are enough. If a section still needs work, let it cool for a few seconds, then go over it again at the lowest setting that works. Holding the plates still on one section for a long time is a common cause of damage, so keep the tool moving at a steady pace and avoid clamping hard, which can crimp fine hair.

Once a curl or wave is formed, let it cool completely before you touch or brush it. Warm hair is still soft and can lose its shape when handled, while cooling helps the curl set. When you brush out the finished style, use a wide-tooth comb or a flexible brush, starting at the ends and working up toward the roots. Clean the plates regularly with a soft cloth, because product buildup can transfer to hair and leave a residue that dulls the finish.

Keep plates and barrels away from the scalp, ears, neck and fingers, and rest a hot tool on a heat-resistant surface rather than a towel or bedding. Keep corded tools away from water and sinks, and unplug the tool and let it cool before you store it.

Using heat less often matters as much as using it well. Many waves and curls can be set without heat by braiding damp hair overnight or wrapping it around soft rollers, and letting hair air-dry when you have the time is the gentlest option of all. Let any heatless set dry completely before you take it out. If hair keeps breaking even with gentler habits, a licensed hairstylist can check your technique and tools in person.