Curls in straight hair: why they fall out and how to make them last longest

Last updated: 21 October 2026

Is your hair naturally straight, and do you see a curl disappear again within an hour? That's not because you're clumsy with the flat iron. Straight hair simply holds a curl differently from hair with more natural wave, and there's a clear reason for that. In this article you'll first read why that happens, and then what you can achieve with the right preparation and technique.

Why does straight hair let go of a curl so quickly?

Straight hair is naturally smooth. The outer layer of each hair, the cuticle, lies flat and tight, so it gives the curved shape of a curl little to hold on to. A curl is a temporary shape that your hair keeps as long as it stays dry. As soon as moisture gets in, from the air or from your own scalp, the hair goes back to its original, smooth shape. With straight hair that happens faster than with hair that has more natural wave, because the cuticle gives less grip and a thicker section pulls down harder.

Two things play a role here. First, the weight of the section you curl: the thicker and heavier the section, the faster that weight pulls the curl straight again. Also read our guide on how much hair to take at a time. Second, the smoothness of the cuticle itself. NEMO Kennislink explains why hair frizzes in humid weather: moisture in the air creates new, temporary bonds in the hair that make it change shape. That same effect, moisture setting the hair in motion, also pushes a freshly made curl in straight hair back towards its smooth shape. A closed, smooth cuticle, typical of healthy straight hair, gives less hold than a rougher or more porous structure. De Haarstichting explains that open cuticles let moisture through where closed cuticles keep it out. It's the same principle that makes a smooth cuticle give a curl little grip. Want to read more broadly about how hair gets its shape? Then also take a look at why hair curls.

The honest ceiling for straight hair: what technique does and doesn't fix

Hair structure sets the ceiling of what's possible. Technique decides how close you get to it. Naturally straight hair needs more preparation than hair with more natural wave. With the right preparation and technique, a curl stays beautifully in place in straight hair too.

Have you seen a curl drop within a few hours before? Then there's almost always something to gain in the steps that follow.

Preparation: where it usually goes wrong with straight hair

Hair that's too clean, too smooth or not fully dry takes a curl less well. A smooth section gives little hold, and moisture in the hair pushes the shape straight back. So blow-dry your hair fully before you start styling. With straight hair, styling on the first or second day after washing usually gives more grip than styling on wash day itself, because the hair then feels a little less smooth.

Have you just washed your hair, or does your hair quickly feel flat and smooth? A texture spray or a little dry shampoo on the lengths gives extra hold before you start. It's not a required step, but it is a missed opportunity if you skip it with hair that normally turns smooth quickly.

Step by step: curling straight hair with an airstyler

With your preparation sorted, here are the steps to create the curl as well as possible. You'll need an airstyler or flat iron, a heat protectant, and if you like, a light hairspray to finish.

Heatless curls: why it's a different story for straight hair

Heatless curling works differently from creating a curl with a tool. Instead of setting a new shape in your hair, you wake up your own curl pattern, which is often still invisible. You can do that with rag curls, braids or a scrunchie curl method. With truly straight hair, there's often no wave to wake up, and then this route works poorly or not at all. That's not a question of technique, but of hair structure.

This principle is part of the broader Curly Girl Method, an approach focused on showing your own, natural hair pattern rather than creating an artificial curl. Want to try one of the heatless techniques yourself, for example if your hair does have some natural wave? Our guide on curls without a curling iron shows seven ways and what you can realistically expect from them.

Humidity, weather and the rest of the day with straight hair

Humid weather and sweating do the same to straight hair as moisture from outside: the hair goes back to its smooth, original shape. The more humid the day, the faster that happens, and with straight hair it shows sooner than with hair that has more natural wave. Our guide on keeping curls in humid weather goes deeper into what you can do about it.

Does your curl look good right after styling, and only drop gradually later in the day? Then that's a different issue from the one this article is about. In that case, read on in why curls drop quickly and what to do about it.

Frequently asked questions

Can straight hair be curled?

Yes. With heat, that works for almost every hair type, including hair that's completely straight by nature. Without heat, the result depends on how much natural wave your hair already has: the straighter your hair is by nature, the less a heatless method will give you.

Why won't my straight hair stay curled?

Usually it's the combination of a smooth cuticle and moisture pulling the hair back to its original shape, as we explain above in "Why does straight hair let go of a curl so quickly?". For most straight hair types, preparation, technique and a light setting spray can make the difference between a curl that's gone after an hour and a curl that stays.

How do you get curls if you have straight hair?

Follow the step-by-step plan above, from protection to setting. With straight hair, the order of the steps matters just as much as the steps themselves.

Can you also curl straight hair with an airstyler?

Yes, the principle is the same as with a flat iron: wind the hair, heat it and let it cool before you release it. The difference lies in the heat setting and the thickness of the section you take, and with straight hair that matters a little more than with hair that already has some natural wave.

Written by Anne Leensen, Ace & Taylor

Sources: NEMO Kennislink, "Waarom pluist haar als het vochtig is en helpen haarproducten het voorkomen?" (in Dutch). De Haarstichting, "Droog haar" (in Dutch).