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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
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
9,019 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
86 Reviews
Bestselling mask scented with Floating Forest biotech fragrance
K18 molecular repair hair oil
4.8
Rated 4.8 out of 5 stars
1,000 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 9,019 reviews
93%would recommend these products
Reviews Summary
Customers say this leave-in hair mask transforms their hair texture and manageability after just one use. Many reviews mention noticeable improvements in softness and reduced frizz. Users with curly, fine, and color-treated hair report positive results. The mask works well for various hair types, with many noting improved texture and easier styling. While some mention the product's high price point, most find a little goes a long way. A few users recommend using conditioner alongside the mask for best results. Reviews consistently highlight the mask's effectiveness for addressing dry, brittle hair concerns.
Customers Talked About
9,019 reviews
  • Nataliia M.
    Verified Buyer
    Reviewing
    Jumbo Leave-In Molecular Repair Hair Mask 100mL
    I recommend this product
    Age 45 - 54
    Hair Concern Chemical damage, Dryness, Fragile/brittle hair, Heat damage, Frizz
    Hair Type Medium Density
    My Results Visible Difference, Stronger Hair, Less Breakage, Less Frizz, Shinier Hair
    Rated 5 out of 5 stars
    49 minutes ago
    Great!

    Absolutely love this hair mask! It made my hair feel softer, smoother, and healthier after just a few uses. The texture is lightweight and doesn’t weigh my hair down. My hair looks shinier and feels more repaired and hydrated. Definitely worth trying!

    K Profile picture for K18Hair
    K18Hair
    4 minutes ago

    Thank you for your amazing review, Nataliia! We're absolutely thrilled to hear that the Jumbo Leave-In Molecular Repair Hair Mask is delivering such incredible results for you! It's wonderful that you're seeing softer, smoother, and healthier hair after just a few uses - that's exactly what we love to see. We're so happy the lightweight texture works perfectly for your hair without weighing it down, and that you're noticing that beautiful shine and improved hydration. Thank you for choosing K18 and for sharing your experience with us! ✨

  • Lindsey F.
    Verified Buyer
    Reviewing
    Mini Leave-In Molecular Repair Hair Mask 15 mL
    I recommend this product
    Age 65+
    Hair Concern Chemical damage, Heat damage, Frizz, Dryness
    Hair Type Thick/Coarse, Grey Hair
    My Results Visible Difference, Stronger Hair, Smoother Hair, Less Breakage, Less Frizz
    Rated 5 out of 5 stars
    2 hours ago
    Leave in molecular repair mask

    Seems to work extremely well on my damaged over processed hair. I tried a sample first and ended up buying more. I’m happy with the results.

    K Profile picture for K18Hair
    K18Hair
    1 hour ago

    Thank you for the wonderful review! We're so happy to hear the Leave-In Molecular Repair Mask is working extremely well for your damaged hair. Thanks for sharing your experience!

  • Dena F.
    Verified Buyer
    Reviewing
    Full-Size Leave-In Molecular Repair Hair Mask 50mL
    I recommend this product
    Age 18 - 24
    Hair Concern Split-Ends
    Hair Type Fine/Thin
    My Results Less Frizz, Visible Difference, Less Breakage, Smoother Hair
    Rated 5 out of 5 stars
    3 days ago
    Good stuff

    I have very baby fine hair. I have been struggling to find a shampoo and conditioner that will make my hair look, soft and shiny and not weighed down and drab. I've only been using this for two weeks so far so good definite improvement in the texture my hair softer and shinier. I can't use the hair oil because it's too heavy for my hair., I will keep working with it. The molecular hair oil works really well from my daughter's hair and my son. I love how this company gives out decent samples too. It's such a good way to share with other people and then try the product before you wired to see if it works well for you or not.

    K Profile picture for K18Hair
    K18Hair
    3 days ago

    Thank you for the wonderful review! We're so happy to hear the Molecular Repair Hair Mask is making your fine hair softer and shinier. Thanks for sharing your experience!

  • 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
    5 days 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.

    K Profile picture for K18Hair
    K18Hair
    5 days 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
    1 week 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

    K Profile picture for K18Hair
    K18Hair
    5 days 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. ✨😊

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