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4.7
Rated 4.7 out of 5 stars
8,125 Reviews

full-size leave-in molecular repair hair mask

4-minute leave-in treatment to reverse hair damage

Description

A leave-in treatment mask that works on the molecular level to reverse hair damage in just 4 minutes. The K18PEPTIDE™ is clinically proven to repair damage from bleach + color, chemical services and heat* – with immediate and lasting results to restore strength, softness, smoothness and bounce to hair.

20+ billion TikTok views 🔥

*Disclaimers

Repairs Damage Caused By

  • Bleach + Color
  • Heat
  • Chemical Services
  1. Shampoo, do not condition. Towel-dry thoroughly.
  2. Apply 1-3 pumps of K18 leave-in molecular repair hair mask based on your length and density, starting at the ends and working up towards the roots.
  3. Let sit for 4 minutes. Do not rinse out.
  4. Comb, add product + style as usual. Use for 4-6 washes post-salon service, then as needed.
  • K18PEPTIDE™ is a biotech-developed peptide that mimics hair's structure to reverse damage by reconnecting polypeptide chains and disulfide bonds broken during bleaching, color and chemical services + heat*.

  • pH-optimized (5.0-6.0) to help minimize cuticle swelling + put hair proteins in their most resilient state.

  • Cream format enables easy, lightweight application across all hair types, with detangling and softening benefits.

  • Vegan, color-safe, cruelty-free.

Takes damage repair further – reconnects both polypeptide chains (and as a result, also reconnects disulfide bonds) for strength along the length + width of the hair - offering comprehensive, lasting damage repair.

Restores hair from even extreme damage - by working at the innermost layer of the hair, core strength and elasticity are renewed for strong, smooth, bouncy hair.

Delivers immediate and lasting results – hair is repaired from the first use and lasts past your next wash, for ongoing reparative benefits.

Simplified repair - convenient, leave-in formula works in just 4 minutes, with no extra rinse required.

Works on all hair types – because K18PEPTIDE™ works on a molecular level (where all hair is the same), this product is effective on all hair types.

  • DO clarify before K18 if you’re a heavy product user (demineralize for mineral + metal buildup).
  • DO apply on clean, damp hair.
  • DO wait the full 4 minutes before combing or styling.
  • DO add whatever styling products you love after the 4 minutes.
  • DO use for 4-6 shampoos consecutively for progressive results.
  • DON'T use conditioner before applying K18 Mask (you can apply after the 4 min but most find they don’t need it).
  • DON'T overdo it—less is more.
  • DON'T rinse it out.

Water (Aqua) (Eau), Alcohol Denat., Propylene Glycol, Cetearyl Alcohol, Dicaprylyl Ether, Cetyl Esters, Behentrimonium Chloride, Polysorbate 20,sh-Oligopeptide-78 (K18PEPTIDE™), Hydrolyzed Wheat Protein, Hydrolyzed Wheat Starch, Isopropyl Alcohol, Tocopherol, Phenoxyethanol, Potassium Sorbate, Citric Acid, Fragrance (Parfum), Geraniol, Linalool, Hexyl Cinnamal, Benzyl Alcohol.

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Color-safe, non-stripping clarifying shampoo with the K18PEPTIDE™

Description

A leave-in treatment mask that works on the molecular level to reverse hair damage in just 4 minutes. The K18PEPTIDE™ is clinically proven to repair damage from bleach + color, chemical services and heat* – with immediate and lasting results to restore strength, softness, smoothness and bounce to hair.

20+ billion TikTok views 🔥

*Disclaimers

got questions?
Get started here.
The K18 mask works as a treatment to reverse damage in 4 minutes. It’s powered by our biomimetic K18PEPTIDE™ to seamlessly fit in and reconnect broken polypeptide chains at the molecular level. As a result, disulfide bonds are also reconnected for reinforced strength along the length + width of hair—offering comprehensive, lasting, and progressive repair.
K18PEPTIDE™ is a biotech-developed peptide that mimics hair’s structure to reverse damage by reconnecting polypeptide chains and disulfide bonds broken during damage from bleach + color, chemical services, and heat*

*k18hair.co.uk/disclaimers
Conditioner leaves a film that blocks our peptide from penetrating effectively. Once the 4-minute wait time is up, feel free to use a conditioner, a leave-in, or any type of product.
We like to keep our formulas minimal, only using the exact amount of ingredients needed to get the peptide where it needs to go. Here the alcohol serves as an agent to optimize the hair environment for the K18 mask to work on a deeper level. Our unique blend of 3 alcohols functions to open the hair cuticle so the K18PEPTIDE™ can penetrate the innermost layer of hair, reaching the broken polypeptide chains (keratin chains).
Most see results after 2-3 uses. The more damaged the hair, the more dramatic the results so it may vary depending on your hair type and level of damage.
powered by K18PEPTIDE™

Biomimetic peptide clicks into hair’s keratin structure—the source of core strength—for soft, shiny, bouncy results that won’t wash away.

how to use molecular repair mask
1. Shampoo, do not condition. Towel-dry thoroughly.

2. Apply 1-3 pumps based on your length and density, starting at the ends and working up towards the roots.

3. Let sit for 4 minutes. Do not rinse out.

4. Comb, add styling product + style as usual. Use for 4-6 washes, then as needed.
feel what's possible with K18
See how K18 unlocks our community's expression
4.7
Rated 4.7 out of 5 stars
Based on 8,125 reviews
93%would recommend these products
Reviews Summary
Customers say this hair mask transforms damaged, bleached, and chemically-treated hair, making it softer, stronger, and more manageable. Many report significant improvements in hair texture, with reduced breakage, split ends, and frizz. Users with curly hair find it enhances curl definition and reduces dryness. The lightweight formula doesn't weigh hair down or leave residue. Many reviews mention it works particularly well for bleached hair, helping restore smoothness and shine. Some note the price is high but find it worthwhile since only small amounts are needed per use.
Customers Talked About
8,125 reviews
  • Lilia H.
    Verified Buyer
    Reviewing
    Full-Size Leave-In Molecular Repair Hair Mask 50mL
    I recommend this product
    Age 35 - 44
    Hair Concern Chemical damage, Color-care, Frizz, Dryness
    Hair Type Thick/Coarse
    My Results Stronger Hair, Visible Difference, Less Frizz, Smoother Hair, Soft Touchable Hair
    Rated 5 out of 5 stars
    21 hours ago
    1st noticed difference

    Had drastic issues with my hair after my last bleach and a previous hairstylist recommended this product. I instantly noticed a change in my hair after first use. My natural curls are back. Excited to see the results after more uses.

    KU Profile picture for K18Hair UK
    K18Hair UK
    20 hours ago

    Thank you for your amazing review, Lilia! 💛 We're thrilled the Leave-In Molecular Repair Hair Mask brought your natural curls back after bleach damage. Excited for your continued results! ✨😊

  • Heather H.
    Verified Buyer
    Reviewing
    Jumbo Leave-In Molecular Repair Hair Mask 100mL
    I recommend this product
    Age 25 - 34
    Hair Concern Heat damage, Chemical damage, Fragile/brittle hair, Dryness, Split-Ends
    Hair Type Thick/Coarse, Curly/Coily
    My Results Visible Difference, Stronger Hair, Less Breakage, Smoother Hair, Defined Curl/Wave Pattern
    Rated 5 out of 5 stars
    2 days ago
    Amazing

    The one item I will splurge on and purchase over and over. The only thing that has saved my bleached hair. Well worth the price

    KU Profile picture for K18Hair UK
    K18Hair UK
    2 hours ago

    Thank you for your amazing review, Heather! 💛 We're so thrilled to hear that the Jumbo Leave-In Molecular Repair Hair Mask has become your go-to splurge and is saving your bleached hair. It means the world to us to know that K18 has earned such a special place in your routine! Thank you for your continued support and for sharing your experience with us. ✨😊

  • Kayla H.
    Verified Buyer
    Reviewing
    Jumbo Leave-In Molecular Repair Hair Mask 100mL
    I recommend this product
    Age 25 - 34
    Hair Concern Chemical damage, Dryness
    Hair Type Straight/Wavy
    My Results Less Breakage, Smoother Hair
    Rated 5 out of 5 stars
    2 days ago
    love!!

    my hair has been bleached multiple times and instantly feels better as soon as this mask touches it :’) finally starting to be able to grow my hair out healthily !!

    KU Profile picture for K18Hair UK
    K18Hair UK
    3 hours ago

    Thank you for the incredible review! We're so thrilled to hear the Jumbo Leave-In Molecular Repair Hair Mask is helping your bleached hair feel better and that you're finally able to grow it out healthily. There's nothing better than seeing damaged hair transform! We appreciate you sharing your experience and for being part of the K18 community!

  • Christina N.
    Verified Buyer
    Reviewing
    Full-Size Leave-In Molecular Repair Hair Mask 50mL
    I recommend this product
    Rated 5 out of 5 stars
    5 days ago
    Great product

    So easy to use light and not sticky. I’ve noticed less hair fall out and receive many comments on how healthy my hair look and asked what I use.

    KU Profile picture for K18Hair UK
    K18Hair UK
    4 days ago

    Thank you so much, Christina! We're thrilled to hear the Leave-In Molecular Repair Hair Mask is working so well for you and that it feels light and non-sticky. It's amazing that you're experiencing less hair fall and getting compliments on how healthy your hair looks — that's exactly what we love to hear! ✨ Thank you for sharing your experience with us!

  • Jorge C.
    Verified Buyer
    Reviewing
    Jumbo Leave-In Molecular Repair Hair Mask 100mL
    I recommend this product
    Age 18 - 24
    Hair Concern Chemical damage, Split-Ends
    Hair Type Fine/Thin, Medium Density
    My Results Less Breakage, Stronger Hair, Smoother Hair, Soft Touchable Hair, Shinier Hair
    Rated 5 out of 5 stars
    6 days ago
    I love this hair mask!!

    Si far I’ve used it once.. because you’re supposed to apply and then leave it for 4 to 6 washes so it’s been a minute. I wanted to see how my hair reacted to it and so far it’s been great. My hair feels softer. I don’t see white tips meaning split ends it’s like a magic eraser honestly, of course it’s not gonna heal completely all really chemically damage hair in one go which is my case. . I did a nanoplasty, which is similar to keratin treatment… my hair was already very dry and brittle and chemically treated before I got in my hair every color of the rainbow for me to end up with dark brown hair, dyed red for years it just it was bad…because of how dry it was I got to the point where it was like super frizzy and I wanted it to be straight and shiny like a lot of the videos on TikTok so I got it done and that just fried my hair completely at least the tips… it was so bad that in the first picture that I attached my all of my hair on the tips started bending in weird ways. It didn’t matter if I dried it with a hairdryer air dried it anything it was bending weird like it was getting almost curly, but I didn’t have any pattern. It was bad like you would touch my hair and it was feeling soft and then the tips super coarse and dry.. it almost felt like if you were touching a broom like it was bad. at some point I kind of started cutting the tips because I was like there’s no fixing this. Tried everything in the book her mass treatments anything I didn’t know about K18.. my hair…

    KU Profile picture for K18Hair UK
    K18Hair UK
    4 days ago

    Thank you so much for sharing your experience, Jorge! We're so happy to hear the Jumbo Leave-In Molecular Repair Hair Mask is already making such a difference after just one use. It sounds like your hair has been through a lot, and we completely understand how frustrating that journey must have been. We're thrilled that you're already noticing softer hair and fewer split ends - that's exactly what our mask is designed to do! We know it takes time to repair severe damage, but it sounds like you're on the right track. Thank you for giving K18 a try and for taking the time to share your detailed review with us ✨

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