K18 Heat Bounce Conditioning Heat Protectant: Guru Score 72%

What the experts use it for.

The concerns the experts tie this product to, in their own words. Paid and founder takes don't count.

Damaged or breaking hair2 experts

“Not only does it protect [...] your hair from heat of styling, it also helps to reduce breakage and strengthen your hair fibers because it's got that biomimetic K18 peptide.”

Dr. Jenny Liu, watch at 19:17

Frizz1 expert

“If you are prone to frizziness, this tames it down and it does an amazing job.”

Sincerely Miss Ash, watch at 32:54

What the gurus are saying.

Every take we've logged from this product's reviews across YouTube. Click any row to watch the moment they said it.

All takes Yay takes Nay takes Mixed takes Hide sponsored

Sincerely Miss Ash

196k subs

~Yay

"This is the leave-in conditioner and heat protectant I've been raving about for a while, it launched late summer or early fall last year and I've used it ever since. I just finished it three weeks ago and pulled out a new one, [...] and I wash my hair two to three times a week, [...] so it lasted a very long time. It [...] really conditions the hair, leaving it super soft, smooth, and shiny, and it tames down frizz while protecting hair from heat styling up to 450 degrees Fahrenheit."

All 6 takes from Sincerely Miss Ash

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"This really leaves your hair super soft and shiny. If you are prone to frizziness, this tames it down and it does an amazing job. My hair is so soft after I use this. And my hair smells amazing after I use this as well. It has a really nice scent. It's not overly strong, but there is a good scent there. [...] This is exceptional, and this has to be one of the best that I have ever used on my hair personally. This makes a big difference for sure."

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"If you're someone with frizzy hair, this really helps to tame the frizz as well. And I am obsessed with this. This is my second bottle. I have a third one already in my linen closet ready to go. I will never be without this. [...] I like this a lot more because of the technology and the way that it makes my hair look and feel. This is 10 out of 10. I've never used anything like this, and I really do recommend this for everyone, whether you color your hair or not."

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"This is their new Heat Bounce Conditioning Heat Protectant. [...] Anything that is new in the K18 brand, I want to try it because this brand has really improved my hair, especially the leave-in molecular hair mask. I have been really consistent with that hair mask, and I have seen a big difference with my hair. It's a lot healthier. It's a lot shinier. It's softer, and it looks so much better than what my hair looked like 6 years ago. [...] This contains a patented technology with Rasilicor."

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"This is phenomenal. This is the best leave-in product I have ever used. This has a patented Rasilicore technology that protects your hair from heat styling tools up to 450 degrees Fahrenheit. But it's going to protect the cuticle of your hair as well as the cortex of the hair. So the outside and in. Most heat protectants only protect the cuticle of the hair. This has that patented technology that's going to deeply protect from heat styling tools. It's more of that intense protection."

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"I love the K18 brand and this product really is 10 out of 10. [...] Not only does it make my hair super soft and shiny, but I have more trust in this when I am using heat styling tools. [...] I've experienced a lot of breakage and heat damage in the past and I just feel more confident using this prior to my heat styling tools, whether that's blow drying my hair, curling my hair, straightening my hair, whatever."

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"This is the leave-in conditioner and heat protectant I've been raving about for a while, it launched late summer or early fall last year and I've used it ever since. I just finished it three weeks ago and pulled out a new one, [...] and I wash my hair two to three times a week, [...] so it lasted a very long time. It [...] really conditions the hair, leaving it super soft, smooth, and shiny, and it tames down frizz while protecting hair from heat styling up to 450 degrees Fahrenheit."

Abbey Yung

887k subs

~Nay

"Liked it but didn't hate it and didn't love it. [...] Not something that feels worth it to splurge on when there are so many other leave-in sprays that are really loved that are significantly less money."

All 3 takes from Abbey Yung

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"Liked it but didn't hate it and didn't love it. [...] Not something that feels worth it to splurge on when there are so many other leave-in sprays that are really loved that are significantly less money."

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"I didn't hate this and didn't have the tangling issues I had with Iron Sleek, but I also just wasn't obsessed with it, I don't feel like I get quite as much softness, smoothness, and slip as with my favorite leave-in conditioners. When a product is on the more expensive side I need to feel like it's worth every penny, and I just don't feel that way about this one, whereas I do feel that way about K18's treatment."

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"It was a Sephora purchase. [...] For everybody who has wanted to know my thoughts on this, I have to say I don't hate it, but I don't love it. When I compare this to my favorites, I just don't feel like the results are quite as good. I'm not getting as much slip for easier detangling. It's not smoothing as much. It's not softening as much. It's not helping to prevent frizz as much. It's just not quite on that same level as my favorites in terms of how it makes my hair look and feel."

Dr. Jenny Liu

324k subs

~Yay

"This one from K18 is a lovely one. Not only does it protect [...] your hair from heat of styling, it also helps to reduce breakage and strengthen your hair fibers because it's got that biomimetic K18 peptide. Love the texture because it's light. It's nourishing but not heavy. So it also helps to soften and smooth your hair at the same time. So you're protecting your hair but also doing something good for your hair at the same time."

No BS Beauty

89k subs

~Mixed

"K18 has a new leave-in conditioner heat protectant. I use this a couple times a week. [...] This one does have a strong smell. It dissipates and it's not superly offensive like some other ones are. But I'm curious how this leave-in conditioner smells because leave-in conditioner tends to be more noticeable to me."

JG

Jamie Genevieve

974k subs

~Yay

"I got the K18 Heat Bounce Conditioning Heat Protectant because heat protectant is actually one place that I am not always great. I don't always use it. So I wanted to get a really nice one that had great reviews so I can look after my hair."

What the evidence says.

Independent of what the gurus think, this is what the published research supports about the main active ingredients here.

Alpha hydroxy acids

Alpha hydroxy acids loosen the bonds holding dead cells at the surface. The evidence supports smoother texture and more even tone over time, and they can leave skin more sensitive to sun.

Source: NIH, National Library of Medicine

Peptides

Peptides are short protein fragments meant to signal repair. The evidence for them is thinner than for retinoids or vitamin C, and it varies a lot by the specific peptide, so the category is more promising than proven.

Source: NIH, National Library of Medicine

Vitamin E

Vitamin E is an antioxidant, and it is often in a formula to keep the other ingredients stable rather than as the active itself. It pairs well with vitamin C, though on its own the evidence for visible change is limited.

Source: NIH, National Library of Medicine

Frequently asked.

What is K18 Heat Bounce Conditioning Heat Protectant?

A leave-in conditioning heat protectant from K18, designed to shield hair from heat styling tools while softening and smoothing it.

Is K18 Heat Bounce Conditioning Heat Protectant worth it?

The gurus mostly approve it, but with enough reservations to keep it in the middle at a Guru Score of 72%.

What is K18 Heat Bounce Conditioning Heat Protectant's Guru Score?

K18 Heat Bounce Conditioning Heat Protectant holds a Guru Score of 72%. That is our read on how warmly the experts talk about it, based on the verdicts of 5 expert reviewers we have collected.

What is K18 Heat Bounce Conditioning Heat Protectant good for, according to the experts?

In their reviews, experts say K18 Heat Bounce Conditioning Heat Protectant is good for damaged or breaking hair (2 experts) and frizz (1 expert).

Is K18 Heat Bounce Conditioning Heat Protectant good for damaged or breaking hair?

2 experts who reviewed K18 Heat Bounce Conditioning Heat Protectant say it is. Dr. Jenny Liu put it this way: “Not only does it protect [...] your hair from heat of styling, it also helps to reduce breakage and strengthen your hair fibers because it's got that biomimetic K18 peptide.”