Name: Leave-In Molecular Repair Hair Mask 50mL
Brand: K18Hair
Price: 75.00 USD
Availability: InStock
Rating: 4.7 (1366 reviews)

leave-in molecular repair hair mask

4-minute leave-in treatment to reverse hair damage

Rated 4.7 out of 5

Based on 1366 reviews

An at-home leave-in treatment infused with our patented K18Peptide™ that works to repair even the most extreme damage, renewing hair to its most youthful, healthy state.

Repairs Damage Caused By

Bleach + Color
Heat
Chemical Services

Full Size - $75.00 50 mL Try-it Size - $12.00 5 mL

FREE SHIPPING. FREE RETURNS.

more to know

creates hair like new
Traveling deeper into the inner layers of hair than traditional repair products, our revolutionary patented K18Peptide™ is just the right size and makeup to fit in and reconnect broken keratin chains, renewing hair with strength, softness, smoothness, and bounce. You can feel and see the difference with the first use.

See dosage chart for exact usage. For best results, use for the first 4-6 consecutive washes, then every 3-4 washes as needed to maintain hair strength.

how to use

IN the shower

Shampoo, do not condition.

OUT of the shower

Towel dry thoroughly.
Begin with 1 pump of the K18 Mask and add more as needed depending on the length, thickness, and condition.
Work evenly into hair from ends to roots, one pump at a time.
Let sit for 4 minutes to activate.
Do NOT rinse out.
Style as usual.

Dosage Guide:

do's + don'ts

DO use a clarifying shampoo if you’re a heavy product or dry shampoo user to remove buildup and help our peptide penetrate and get where it needs to go.
DO wait the full 4 minutes before styling or applying other product
DO use every 4-6 shampoos consecutively to see and feel ongoing results

DON’T condition your hair before application (trust us, most won’t need it after K18, if you still need, add a leave-in after the 4-minute window is up post-application)
DON’T overuse, a little goes a long way.
DON’T rinse out. This is a leave-in, so you know, leave it in!

key benefits

Our K18Peptide™ is clinically proven to reverse damage in just 4 minutes.

Heals damage from bleach, color, chemical services, and heat
Restores strength, softness, smoothness, and bounce
Doesn’t wash away with shampoo, leaving lasting results
Vegan, color-safe, cruelty-free

91% original strength*
94% original elasticity*

* Results observed in a clinical study while using mist and mask as part of a bleaching treatment. Results may vary depending on hair type, quality and history.

ingredients

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.

what you can expect
by damage type

backed by science,
loved by stylists

Our community of stylists and colorists believe K18 is liberating hair—no matter the hair type or generation.

“K18 allows me to go everywhere I want to go with my color work and the end result is my guests get to be bright and shiny and healthy.”

– Christine Thompson, Director of Color at Spoke & Weal

have questions?

we have answers.

How does K18 work?

When hair gets damaged, the polypeptide chains (keratin chains) that make up the inner structure of hair strands become weakened and break. For context, there are billions and billions of polypeptide chains (keratin chains) in a single strand of hair. When these are damaged, hair’s core structure responsible for elasticity and strength becomes compromised and as a result it loses its resiliency and shine—or the look and feel of healthy hair.

After spending a decade in the lab scanning and testing all amino acid sequences across the entire keratin genome that makes up human hair searching for a breakthrough, we discovered one unique sequence (a bioactive peptide) that brings damaged hair back to its original, youthful state. This is our K18Peptide™.

Traveling deeper into the inner layers of hair than traditional repair products, our revolutionary peptide is just the right size and makeup to fit in and reconnect those broken polypeptide chains (keratin chains). And because our peptide is a bit of an overachiever, as a result of this reconnection, any disturbed disulfide bonds are also re-conformed.

Our peptideemploys biomimetics to get the job done. To put it simply: Biomimetics is the practice of learning from and mimicking nature. Mimicking the natural structure of keratin building blocks (amino acid sequences), our K18 bioactive peptide is recognized as natural by the hair. It’s not washed away by water or shampoo like traditional bonding agents either, making K18 a genuine, lasting solution for damaged strands.

What is the K18Peptide™?

Our patented peptide is a unique sequence of amino acids that travels deep into hair’s core structure to fit in and reconnect broken polypeptide chains (keratin chains) responsible for hair strength and elasticity.

An Analogy: When building proteins, the order of the amino acids determines the kind of protein and its properties, much like the way letters are arranged to make meaningful words and sentences. In the same way the order and where each word sits in a sentence leads to its overall meaning, K18 is the magic word that fits right in, integrating itself with the keratin chains as the hair recognizes it as a natural building block.

Why should I skip conditioner?

K18 is most effective on clean, towel-dried hair. Conditioners use silicones and conditioning agents that form heavy coatings on hair, preventing our peptide from reaching the broken polypeptide chains deep inside hair’s inner layer.

I noticed there’s alcohol in the formula, isn’t that bad for you?

We like to keep our formulas minimal, only using the exact amount of ingredients needed to get the peptide where it needs to go. Our unique blend of 3 alcohols function to open up the hair cuticle so the K18Peptide ™ can penetrate the inner most layer of hair, reaching the broken polypeptide chains (keratinchains). Here the alcohol serves as an agent to optimize the hair environment for K18 to work on a deeper level.

When should I expect to see results?

You will start to see stronger, softer, healthier hair after just one use.

renews strength, softness, smoothness, and bounce

Curly

Coily

Straight

K18 strengthens hair’s core structure, restoring damaged curl patterns and leaving strands looking and feeling like new.

K18 reconnects broken keratin chains, restoring hairs elasticity and strength meaning coily hair can be renewed and brought back to its original springy, healthy shape.

K18 restores strength, softness, smoothness, and bounce so even the sleekest hair can feel like new.

Reviewed by Deborah

Verified Reviewer

Reviewing

Leave-In Molecular Repair Hair Mask 50mL

I recommend this product

Age

35 - 44

Hair Concern

Chemical damage
Color-care
Fragile/brittle hair
Dryness
Split-Ends

Hair Type

Medium Density
Straight/Wavy
Grey Hair

My Results

Visible Difference
Less Breakage
Stronger Hair
Soft Touchable Hair
Shinier Hair

Rated 5 out of 5

Review posted

Can't believe I waited so long to try this!

After my last bleaching session my hair was the absolute worst it's ever been, which was especially devastating because I spend so much effort protecting it from heat and uv damage. I had seen Jack Martin promote this on Instagram a number of times but decided to try Olaplex and three(!) other repair systems first because they were less expensive. They did little to nothing. FINALLY I decided to buy a sample size and I was blown away. In just ONE treatment, my hair looked better than it has in 2+ years - and that was just air dried with no styling. I can't wait to see what kind of results I'll see as I continue using this. The full-size bottle price is high, ngl, but far less than when you add up all the other useless stuff I bought. I previously dismissed the sample size as it's so small and thought there's no way it could be enough to do anything but I was shocked at the punch packed in there. I've already used it twice and I think I might get another use out of it for my long, medium weight hair. If you have any qualms at all, go ahead and get the sample and you'll see what a quality product this really is.

Was this helpful?

Reviewed by Sarah

Verified Buyer

Reviewing

Leave-In Molecular Repair Hair Mask 5mL

I recommend this product

Age

35 - 44

Hair Concern

Chemical damage

Hair Type

Thick/Coarse

My Results

Smoother Hair

Rated 5 out of 5

Review posted

Good so far!

I’m glad there was a sample version to try before committing to the regular size. Shipping was wildly fast. I’ve been using it for about two weeks so far and my bleached hair definitely feels better than before.

Was this helpful?

Reviewed by Tammy W.

Verified Buyer

Reviewing

Leave-In Molecular Repair Hair Mask 50mL

I recommend this product

Age

45 - 54

Hair Concern

Chemical damage
Heat damage
Fragile/brittle hair
Dryness
Split-Ends

Hair Type

Thick/Coarse
Grey Hair

My Results

Visible Difference
Smoother Hair
Shinier Hair
Less Frizz
Stronger Hair

Rated 5 out of 5

Review posted

Awesomely Smooth

Hair was very dry and split ends showing bad. This product has made it very soft and shiny. It also helps with humidity as it doesn’t frizz up as much. I’ve been using once a week because hair was bad from over processing to let gray come out between low lights. Would definitely recommend.

Was this helpful?

Reviewed by Aimee L.

Verified Buyer

Reviewing

Leave-In Molecular Repair Hair Mask 50mL

I recommend this product

Age

45 - 54

Hair Concern

Frizz

Hair Type

Medium Density
Grey Hair
Straight/Wavy

My Results

Less Frizz
Visible Difference
Stronger Hair
Less Breakage
Smoother Hair

Rated 5 out of 5

Review posted

Great

My hair stayed smooth for weeks after one application

Was this helpful?

Reviewed by Sonja O.

Verified Buyer

Reviewing

Leave-In Molecular Repair Hair Mask 50mL

I recommend this product

Age

35 - 44

Hair Concern

Chemical damage
Fragile/brittle hair
Split-Ends

Hair Type

Fine/Thin

My Results

Soft Touchable Hair
Less Breakage

Rated 5 out of 5

Review posted

Soft hair for days!

My stylist used it on me and I was shocked by how soft my hair was after bleaching it so I just HAD to buy the mask for myself. I only wish there was more in a "full size" bottle for the price I paid.

Was this helpful?