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tile tsa-approved | color: black
4.7
Rated 4.7 out of 5 stars
8,856 Reviews

mini 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 3-9 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
71 Reviews
Bestselling mask scented with Floating Forest biotech fragrance
K18 molecular repair hair oil
4.8
Rated 4.8 out of 5 stars
973 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 8,856 reviews
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.
8,856 reviews
  • Geneve H.
    Verified Buyer
    Reviewing
    Full-Size Leave-In Molecular Repair Hair Mask 50mL
    I recommend this product
    Age 55 - 64
    Hair Concern Heat damage
    Hair Type Grey Hair, Medium Density, Fine/Thin, Curly/Coily
    My Results Visible Difference, Less Frizz, Less Breakage
    Rated 5 out of 5 stars
    14 hours ago
    IT’S WORKING!

    My hairdresser always educates and guides me for my hair care and never steers me wrong. Even with heat protection, I fried my hair pretty good, not to mention I moved from CA to CO and it’s very dry here and water is hard. I knew I would need more than three treatments as you will see in the picture, BUT it’s definitely noticeable. I’m still not putting heat to my hair to give it complete restoration. However, this is worth the money because it DEFINITELY is working. Thank you K18!

  • Isabella L.
    Verified Buyer
    Reviewing
    K18 x Future Society Limited Edition Scent Mask
    I recommend this product
    Age 35 - 44
    Hair Concern Heat damage, Chemical damage, Fragile/brittle hair, Dryness, Split-Ends
    Hair Type Medium Density
    My Results Less Breakage, Shinier Hair
    Rated 5 out of 5 stars
    Yesterday
    Love it!

    Works amazingly!

  • Kiersten V.
    Verified Buyer
    Reviewing
    Full-Size Leave-In Molecular Repair Hair Mask 50mL
    I recommend this product
    Age 25 - 34
    Hair Concern Heat damage, Dryness, Fragile/brittle hair, Chemical damage
    Hair Type Fine/Thin
    My Results Less Frizz, Stronger Hair, Less Breakage, Smoother Hair, Visible Difference
    Rated 5 out of 5 stars
    3 days ago
    HAIR FOOD

    I was honestly at the point where I thought my hair was beyond saving—years of bleaching left it dry, brittle, and constantly breaking. Then I tried the K18 hair mask, and I can genuinely say it completely transformed my hair.

    After just a few uses, my bleach-blonde hair went from feeling like straw to actually soft, smooth, and healthy again. It doesn’t just sit on top of your hair like a typical conditioner—it feels like it actually repairs it from the inside out. My ends look less fried, my hair feels stronger, and I’ve even noticed less breakage when brushing.

    What really surprised me is how lightweight it is. My hair feels silky without being weighed down or greasy, which is rare for something this hydrating. It’s like my hair finally has life in it again.

    If your hair is dry, damaged, or over-processed like mine was, this is absolutely worth it. It didn’t just improve my hair—it genuinely saved it.

    K Profile picture for K18Hair
    K18Hair
    2 days ago

    Thank you so much for your incredible review, Kiersten! 💛 We're absolutely thrilled to hear about your amazing hair transformation - going from feeling like your hair was beyond saving to having it completely transformed is exactly what K18 is all about! ✨ It sounds like you've experienced the true power of molecular repair, and we're so excited that your bleach-blonde hair went from straw-like to soft, smooth, and healthy again. We love that you can feel the difference of how it actually repairs from the inside out rather than just sitting on top like typical conditioners! The fact that you're seeing less breakage, stronger hair, and healthier-looking ends while still maintaining that lightweight, silky feel without any greasiness is absolutely wonderful to hear. Your hair definitely has life in it again, and we couldn't be more excited for you! Thanks for your fantastic 5-star review! 🙌

  • kimberly c.
    Verified Buyer
    Reviewing
    Leave-In Molecular Repair Hair Mask Deluxe Sample
    I recommend this product
    Rated 5 out of 5 stars
    3 days ago
    Miracle!

    This stuff is miracle in a bottle/tube!

    K Profile picture for K18Hair
    K18Hair
    2 days ago

    Thank you so much, Kimberly! 💛 We're absolutely thrilled to hear that the Leave-In Molecular Repair Hair Mask Sample feels like a miracle in a tube for you! That's exactly the kind of transformation we love to see - when our molecular repair technology truly makes that incredible difference you can feel and see! ✨ Your amazing 5-star review means the world to us! 🙌

  • Stephanie E.
    Verified Buyer
    Reviewing
    Jumbo Leave-In Molecular Repair Hair Mask 100mL
    I recommend this product
    Age 45 - 54
    Hair Concern Chemical damage, Fragile/brittle hair, Frizz, Dryness
    Hair Type Fine/Thin, Straight/Wavy
    My Results Visible Difference, Stronger Hair, Defined Curl/Wave Pattern, Smoother Hair, Shinier Hair
    Rated 5 out of 5 stars
    3 days ago
    This stuff works!

    My bleached hair is very damaged due to unsuccessfully tried to go brown over platinum and having to re-bleach my hair. This caused significant damage and breakage- I have areas of breakage all around the top of my head and those areas and my frazzled ends were impossible to get to smooth and had a flat dead look. I have been using k18 treatment for several weeks and I see a big improvement. The broken off areas and my ends are much smoother and shinier. I will mention that I shampoo, use k18, then use a conditioner and my normal styling products. I tried it without conditioner my hair was too dry.

    K Profile picture for K18Hair
    K18Hair
    3 days ago

    Thank you so much for your incredible review, Stephanie! 💛 We're absolutely thrilled to hear about the amazing transformation you've experienced with the Jumbo Leave-In Molecular Repair Hair Mask! Going from damaged, broken areas with a flat, dead look to smoother, shinier hair after several weeks - that's exactly the kind of molecular repair magic we love to see! ✨ It sounds like you've found the perfect routine by incorporating conditioner after the K18 treatment, and we're so glad you've discovered what works best for your bleached hair. Your patience and dedication to the process is paying off beautifully! Thanks for your fantastic 5-star review! 🙌

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