Today, we are tackling a very important question, which is at what temperature to curl hair or how hot should you set your curling iron?
The thing is, there’s not a one-size-fits-all answer. So what I want to do is give you the tools you need to figure out the perfect recipe for your hair.
You have to find the perfect temperature and the perfect amount of time to leave your hair on the iron.
So we’re gonna talk through all of it. We’re gonna sort it out. And at the end, you should be able to start figuring out your own little recipe.
Let’s get into it.
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Table of Contents
What Temperature to Curl Hair?
Going From Hot to Cool
First things first, let’s talk about what actually makes your hair curl, because there are a whole lot of things that we subconsciously believe about curling our hair that are wrong, and it makes us make a lot of wrong decisions with our hair.
It’s easy to think that, okay I’m using this hot tool so it’s the heat that curls my hair. But it’s actually the act of going from hot to cold that curls your hair. And that is incredibly important. The cool thing is is that it’s actually the same thing inside your hair that happens when it goes from wet to dry.
In both cases with heat and with water, the hydrogen bonds in your hair temporarily disconnect and then when your hair dries or gets cool, they reconnect. And that’s why when you put your hair on rollers and you let it dry in that shape, you then have curls.
That’s why when you go to bed with your hair still partially wet, you wake up and it’s in crazy shapes because you laid on it in crazy shapes.
It’s also why humidity is the worst, because it’s just a little bit of water always getting in your hair, always breaking and reforming the hydrogen bonds until your hair goes back to the state that it was before you styled it.
So just like your hair on rollers has to go from wet to dry for those curls to stay, your hair has to go from hot to cool for your hairstyle to stay.
So what I want you to take away from that is that first of all, the cooling of your hair is just as important as the heating of your hair.
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Second of all, all of the hair in your section that you’re curling needs to get evenly warm. If certain areas get a whole lot hotter, and other areas don’t get hot at all, you’re gonna have an extremely uneven curl. So section size is important.
And three, a hotter tool does not equal a better curl. Because your hair has to cool back down into its new shape in order to solidify.
So if you get your hair scalding hot, it’s gonna take forever for that to cool down. And what happens as it’s cooling down, gravity takes control and your hair’s natural texture can fight back a little bit.
So if you have hair that’s naturally straight, you’ve got this cute little springy ringlet that just came off the curling iron but, it’s gonna take two minutes for it to cool down into its new shape. And what happens in those two minutes? It starts stretching and stretching and stretching and all of a sudden at the two minute mark, you’ve got a nice, cool curl but you’ve already lost 50% of it.
That’s why scalding hot doesn’t work. That’s why it’s actually worse than anything else for your hair, because you’re not gonna get the result that you’re going for, and you’re just assaulting the cuticle layer or your hair, and that’s the outside shield of your hair, which you need to protect the inside of the hair. So basically, don’t do it.
So if scalding isn’t the goal, what is?
I would say the goal is hot, because you do need to heat up the hair in order for it to cool in its new shape, but not scalding.
So to me, hot feels like I can handle the hair right after it comes off the curling iron, but it’s not causing me significant discomfort and it’s not burning me or causing pain in any way. If you’re going to that place, you’ve gone too far.
Conversely, it’s not just lukewarm. It’s not just like if I was to go in a sauna and come out and feel my hair, that’s too cool.
Hotter than that, but less than scalding. In the middle, that’s where you wanna be.
So now that we know what the goal is, let’s start talking some numbers.
Density of Hair Strands
The most important thing when it comes to figuring out the actual degrees for your curling iron is the density of your individual hair strands.
Not how much hair you have, but when you feel your individual hair strands, how thick or thin are they?
Because it’s just like pasta. You have like angel hair pasta, and it’s super thin and very, very fine, like fine hair. You don’t have to cook it very, very long, you know? It gets heated through pretty easily. Whereas your big old noodles take longer to cook. It’s gonna take longer to heat through it because they’re more dense.
And that’s exactly how it is for hair.
When you have very, very small individual strands, they don’t take as much heat or as long to heat up. Whereas if you have thick individual strands, they take more heat and maybe a little bit more time to heat up.
To start off, you wanna figure out where in that spectrum you are.
I would liken the finest side of things to being like baby hair. If you feel baby hair it’s just so soft and downy, very, very thin. That’s like the most fine version of hair. So if you’re closer to that end, you have fine hair.
You can be in the middle, by the way. You can find yourself perfectly in the middle or slightly to one side or the other, just keep that in mind.
And then thick hair, I would liken it most to like a majestic horse’s mane. Maybe not all the way that thick, but it’s closer to that.
So hopefully that helps you figure out a little bit of where you are on the spectrum.
And then the only other caveat I need to throw in before I start throwing out some numbers is the amount of damage your hair has, because if your hair is exceptionally healthy like I’ve never colored it, I barely ever use heat on it, it’s so shiny and soft and amazing, you’re gonna be more on the thick hair side of things because your hair can take more. It’s more robust, its cuticle layer is thicker.
Whereas if your hair is more damaged, you enjoy the bottle blonde life, perhaps even the platinum blonde life, or whatever the heck your hair has gone through and it’s more damaged, you’re gonna be more on the fine hair side of things ’cause your hair has already taken a little bit of a beating, it’s gonna heat up a lot easier than super healthy hair.
Just keep that in mind, like figure out where you think you are for the density of your hair, then adjust based on the health of your hair.
Alright, so let’s finally start throwing out some numbers.
For the fine, super damaged hair, I’d say between 250 and 300 is your sweet spot. Maybe closer to 300. The 250s, 280s don’t do a ton unless your hair is very, very fine or very, very damaged.
But in that little vein is where you wanna start.
For those of you with very, very thick hair, I would say start around 400. I don’t like to go very far into the 400 degrees range, but I think that’s a good place to start.
You might find that that’s a little too hot for you, or you might find that you want to go up to like 425, which is okay if your hair is not responding to the 400. Because at that point, you have some beastly strong hair and it’s okay.
So start around the 400 mark, and go up and down depending on how your hair is feeling from there.
And then in the middle, that’s more of like the 350 range. If my hair is freshly bleached or I’ve been styling it a lot recently, I’ll go closer to the 300 range, like 325 is kinda where I go to be a little gentler because my hair is gonna respond a little bit easier. Whereas if your hair is a little healthier, you could kind of bump up to that 375 range if you want to.
So that’s your range to start with for the temperatures.
How Long to Curl
But the next thing we have to talk about with your little hair recipe is how long your hair stays on the curling iron.
Now in my ideal world, your hair goes on the curling iron between five to 10 seconds.
Anything less than five seconds isn’t enough, you want the hair to gradually warm up ’cause it’s gonna give you the best results. Shock and awe, not my favorite method.
But additionally, more than 10, I would say is unnecessary. If your hair is not heated up to that hot point that we’re going for within those 10 seconds, your curling iron isn’t hot enough. You need to warm it up.
Because if you’re waiting more than 10 seconds, it’s not so much that it’s bad for your hair, if your hair isn’t getting to that hot point, it’s that it’s inconvenient and it’s not effective. It’s just there’s no need to do that.
So I would say make your curling iron a little bit hotter and go between five to 10 seconds.
And I did touch on the fact that section size is important. I would say your ideal section feels about as thick as two to three drinking straws.
Just imagine, your waiter came, gave you two straws. Put them together in your fingers, feel how thick that is. Now pick up your hair, and see if you can find that same thickness with your hair. That’s your ideal size section.
Formulating Your Recipe
So now that you have taken in all of that information, we are ready to start formulating your recipe.
First start with the degree setting that you think you need based on your hair’s thickness and its healthiness, and start by putting your two to three drinking straws thick section on your curling iron for five seconds and take it off, then feel your hair.
Does it feel hot, like we’re going for? Or does it feel scalding, is it uncomfortable to handle? Or conversely, is it cold?
If it’s kinda cold, try leaving it on the iron just a little bit longer. You know, eight, 10 seconds. But if that’s not doing it and you’re still not getting to that hot place, you gotta hike up the heat on your curling iron a little bit.
I would say go in 20 to 25 degree increments if you can with your curling iron.
Conversely, if you take it off and it’s way too hot to handle, you need to take down the temperature on your curling iron. Again, 20, 25 degrees. 50 degrees is fine if that’s what your curling iron is set to. Just take it down. And then try the five seconds again, and figure out where you are in that range.
For me, my sweet spot is 350 degrees for five to eight seconds. That works super well for me, gets my hair exactly as hot as it needs to be to change the shape of it, but not take too long to cool down.
And again, that heat is when it feels hot to your hand but it’s not causing severe discomfort or pain. That’s what we’re looking for.
First of all, I think we do a lot of high heat shaming because for a lot of us, people that are in the middle of the spectrum or at the very fine end of the spectrum, 400 degrees is way too much, it’s way more than you need.
Again, because it gets to that scalding place, causes a lot of damage, isn’t super effective.
However, if you are in that thick hair category, it is completely appropriate for you and you do not need to feel high heat shamed.
Because the actual diameter of your hair is so much thicker. It takes a lot more heat to penetrate it.
The other thing is not only is your actual diameter of your hair so much bigger, the cuticle layer, the shield around your hair that keeps the heat from getting in, is so much thicker!
That is why you absolutely do not need to feel bad about using high heat on your hair. It’s the absolute wrong choice for some hair types, but it is the right hair choice for yours.
And I would still encourage using a heat protectant and nourishing your hair and doing all that stuff, but know that is okay to use those higher temperatures because it’s appropriate for your hair type.
And finally, I feel I would be amiss to not talk about the actual cooling process for the hair, because it is as important as the heating process.
The best way to make sure that your hair is going to hold its curl after you let it off the curling iron is to not mess with it.
Don’t brush your fingers through it, don’t start pulling it apart, don’t start Beyonce head flipping. Just leave it until it’s cool. And then you can do what you want, it’s in its new shape.
But don’t mess with it while it’s hot unless you want it to fall.
And two, there are things you can do to actually use that cooling mechanism to your favor. When the hair comes off the curling iron, you can hold it up in its shape for three, four, five seconds. That’s a crucial time for your hair, and its gonna help it just kind of set a little bit more.
It works and it’s a great way to make sure that you’re getting that extra curl in your hair. That can help you use the cooling mechanism to your advantage.
Samantha is a hairstylist with over 12 years of color and stylist experience. She enjoys using her knowledge to create what her clients really want when they sit down in her chair. Her passion is creating unique looks that her clients feel great in.