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Leave-in molecular repair hair mask 50mL
Full-Size Leave-In Molecular Repair Hair Mask 50mL
Red curly hair before and after results using k18.
Grey curly hair before and after results using k18.
Bleach blonde hair before and after results using k18.
Red curly hair before and after results using k18.
get stronger, more resilient hair. left - 8x bleach without K18, right 8x bleach with K18
Full-Size Leave-In Molecular Repair Hair Mask 50mL
the K18 routine
Full-Size Leave-In Molecular Repair Hair Mask 50mL
less is more
works for all hair types
where does K18 fit into your routine?
Full-Size Leave-In Molecular Repair Hair Mask 50mL
Full-Size Leave-In Molecular Repair Hair Mask 50mL
K18 routine guide
tilebestseller | color:black
4.7
Rated 4.7 out of 5 stars
4,687 Reviews

full-size leave-in molecular repair hair mask

4-minute leave-in treatment to reverse hair damage
OR

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.

pairs well with
limited edition
K18 x Future Society leave-in molecular hair mask
4.9
Rated 4.9 out of 5 stars
60 Reviews
Bestselling mask scented with Floating Forest biotech fragrance
K18 molecular repair hair oil
4.8
Rated 4.8 out of 5 stars
964 Reviews
Weightless oil that strengthens, repairs damage + reduces frizz

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*
*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.


*k18hair.com/disclaimers
learn more on our blog
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 4,687 reviews
4,687 reviews
  • Danielle K.
    Verified Buyer
    I recommend this product
    Age 55 - 64
    Hair Concern Dryness, Fragile/brittle hair, Color-care
    Hair Type Medium Density, Straight/Wavy, Grey Hair
    My Results Less Frizz, Visible Difference, Smoother Hair, Soft Touchable Hair
    Rated 4 out of 5 stars
    2 weeks ago
    Super soft and great humidity control

    Just started using the K18 mask. I'm pleased at how soft my processed, menopausal hair is. It's become so dry, but K18 makes it feel and look more like hair again. I was really impressed with how well it controlled humidity induced frizz too - nothing I've tried before has worked so well against humidity.

    K Profile picture for K18Hair
    K18Hair
    1 week ago

    Thank you so much for this wonderful review, Danielle! We're absolutely thrilled to hear how much the K18 mask is transforming your processed hair and bringing it back to life. We're especially excited that you're seeing such impressive results with humidity control! That frizz-fighting power is something we're really proud of, and it sounds like it's making such a difference for you. Thank you for sharing your experience - it truly means the world to us! 💛

  • KanietSE K.
    Verified Buyer
    I recommend this product
    Age 25 - 34
    Hair Concern Chemical damage
    Hair Type Fine/Thin
    My Results Less Breakage
    Rated 4 out of 5 stars
    2 weeks ago
    After perm

    After an unsuccessful perm, I took this mask. As it is written in the instructions, I applied only it 6 times in a row. I'm glad that the smell of burning from my hair is almost gone. Visually, the changes are not as clear as I would like, but I will continue to use. I’m sure it would be better if I give more time

    K Profile picture for K18Hair
    K18Hair
    2 weeks ago

    Thank you so much for taking the time to share your experience with the Leave-In Molecular Repair Hair Mask after your perm situation, KanietSE! We're really glad to hear that you're already noticing the burning smell is almost gone — that's definitely a positive sign that the mask is working to repair the damage at a molecular level.

    We completely understand that visual changes can take time to become more apparent, especially after chemical damage from an unsuccessful perm. You're absolutely right that giving it more time will likely bring better results. The molecular repair process works progressively with each use, so continuing with the treatment as you're doing is exactly the right approach.

    We really appreciate your patience and persistence with the treatment, and we'd love to hear how your hair continues to improve as you keep using the mask. Your hair has been through a lot, so the fact that you're already seeing some positive changes is really encouraging!

  • Lillian D.
    Verified Buyer
    I recommend this product
    Age 18 - 24
    Hair Concern Heat damage, Fragile/brittle hair, Frizz, Split-Ends, Chemical damage
    Hair Type Curly/Coily, Straight/Wavy, Medium Density
    My Results Less Frizz, Defined Curl/Wave Pattern, Cleaner, fresher hair, Less Breakage, Visible Difference
    Rated 5 out of 5 stars
    4 weeks ago
    Good Progress So Far

    I have used this product a few times so far and have already seen great results and improvements. I’d like to keep up with it consistently and come back with update photos!

    K Profile picture for K18Hair
    K18Hair
    3 weeks ago

    Thank you so much for your incredible review, Lillian! We're absolutely thrilled to hear that our Full-Size Leave-In Molecular Repair Hair Mask is already delivering great results and improvements after just a few uses - there's no better compliment than knowing our molecular repair technology is working so beautifully that you're excited to keep up with it consistently! We'd love to see those update photos when you're ready to share your continued progress! ❤️

  • Nancy J.
    Verified Buyer
    I recommend this product
    Age 45 - 54
    Hair Concern Chemical damage
    Hair Type Curly/Coily
    My Results Less Breakage, Bouncy Hair
    Rated 5 out of 5 stars
    1 month ago
    Love this hair mask

    This mask has saved my hair!

    K Profile picture for K18Hair
    K18Hair
    4 weeks ago

    Thank you so much for your incredible review, Nancy! We're absolutely thrilled to hear that our Full-Size Leave-In Molecular Repair Hair Mask has saved your hair - there's no better compliment than knowing our molecular repair technology is giving your hair the rescue it needed! ❤️

  • Sadie M. G.
    Verified Buyer
    I recommend this product
    Age 45 - 54
    Hair Concern Chemical damage, Heat damage, Color-care, Frizz, Split-Ends
    Hair Type Thick/Coarse
    My Results Less Frizz, Visible Difference, Stronger Hair, Less Breakage, Smoother Hair
    Rated 5 out of 5 stars
    1 month ago
    Omg this treatment is Amazing!

    I have tried all kind of hair treatments but this one is the best on the market. Kinda expensive but you get excellent results so worth it.

    K Profile picture for K18Hair
    K18Hair
    1 month ago

    Thank you so much for your incredible review, Sadie! We're absolutely thrilled to hear that our Full-Size Leave-In Molecular Repair Hair Mask stands out as the best treatment you've tried after testing so many different options - there's no better compliment than knowing our molecular repair technology is delivering such excellent results that make the investment truly worth it for you! ❤️

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