Beauty product of the week: K18 Leave-In Molecular Repair Hair Mask review

Posted: 13 May 2022 2:44 pm

Is this 4-minute leave-in treatment the new Olaplex?

If your hair is looking a little tired and thirsty, you need to get around the new K18 Leave-In Molecular Repair Hair Mask. Regularly compared to crowd fave Olaplex, I was very excited to give the K18 peptide treatment a go when it came across my radar. Before we get into the review, we should note that this product was gifted but with no obligation to review or post.

About the product

The K18 Leave-In Molecular Repair Hair Mask contains patented bioactive peptides that repair the keratin within your hair cuticles. This helps strengthen your locks and improve elasticity while also making it feel softer and look shinier. From straight to coiled, it's suitable for all hair types and is especially ideal if you have damaged or dry hair.

It only takes 4 minutes to work and can be used instead of conditioner after you've washed and towel-dried your hair. This is because the silicones or conditioning ingredients in your conditioner will apply a heavy coating on the hair, which will prevent the peptides in the mask from getting to the broken polypeptide chains that are deep inside the hair's inner layer.

It's also vegan and cruelty-free and doesn't contain parabens or sulphates, which is always a vibe.

@na.namiicho permanent bleach/heat damage repair w @K18 Hair 😱 join #k18hairflip challenge to win 1/10 $1000 Sephora gc & insalon treatment 😍 #K18partner #hair ♬ #K18hairflip - K18 Hair

The review

K18 Leave-In Molecular Repair Hair Mask | RRP $94.50

To give you some context: I have long, naturally curly hair with bleach blonde money pieces at the front and balayage. I also style my hair with heat tools pretty much everyday. So my hair definitely benefits from these types of products.

I used the K18 leave-in treatment 1–2 times a week for around a month. Once I have washed and lightly dried my hair, I pop 2–3 pumps into my hands, rub them together to emulsify the product and then scrunch it in from my ends to the top of my hair. I try to apply the product all over my hair, but especially concentrate on the ends and bleach-damaged sections of my hair. On application, the product already feels super nourishing. It only takes 4 minutes to activate and you don't need to rinse it out. Just make sure to wait that full 4 minutes before you blow-dry or apply any other products.

Pro tip: If you're like me and your hair puts up a fight when you don't use conditioner (which is a common concern according to TikTok comments), you can always give it a little spritz with a leave-in conditioner after the 4 minutes is up. This will make it easier to detangle and style (my go-to is the Gisou Leave-In Conditioner).

After the first use, I noticed it already looked shinier and less frizzy than usual after blow-drying. After using the product at least once a week for the last month, I've also experienced less breakage in sections of my hair that are heavily bleached. I've also received heaps of compliments from friends and strangers about how healthy my hair looks, which is a big ol' plus.

As you can see in the before and after pictures below, I even coloured my hair in this time and still found that it looked healthier as a result of using the K18 mask.

K18 hair review before and after.

K18 vs Olaplex: How do they compare?

The K18 Hair Mask is regularly compared to both Olaplex in-salon treatments and the No.3 Hair Perfector, which is considered one of the best hair masks in Australia.

While the Olaplex No.3 Hair Perfector and K18 Leave-In Molecular Repair treatment offer similar benefits for damaged hair, they have their own patented formulas. Olaplex rebuilds bonds that break from heat, water and colour damage. K18 also does this in addition to rebuilding the keratin chain of your hair cuticles, which will arguably offer better long-term results. While I enjoy both products, I saw results quicker with the K18 treatment and therefore it sits a little higher on my list.

Final verdict

If you've done your hair dirty with bleach, colour or heat damage, I suggest you apologise to it immediately by way of the K18 Leave-In Molecular Repair Hair Mask. After using it for a month, I'm happy with both the short- and long-term results. My hair looks healthier, feels stronger and it's really easy to work into my existing hair care routine.

$94.50 may seem a little 'spenny for a hair mask, but you'll get approximately 50 uses out of the 50ml bottle. That's only $1.89 per use, which I'd say is pretty damn reasonable for at-home hair repair. It is also available in a travel-sized 5ml bottle for $15. Even though this bottle was gifted, I would definitely invest in this product in the future.

Where can I buy it?

You can shop the K18 Leave-In Molecular Repair Hair Mask at Adore Beauty, Sephora and AMR Hair & Beauty.

Looking for a beauty bargain? Check out all the latest health and beauty coupon codes or shop across 40+ beauty sites that offer free shipping.

Latest shopping news, reviews and guides

Get more from Finder

Ask an Expert

You are about to post a question on

  • Do not enter personal information (eg. surname, phone number, bank details) as your question will be made public
  • is a financial comparison and information service, not a bank or product provider
  • We cannot provide you with personal advice or recommendations
  • Your answer might already be waiting – check previous questions below to see if yours has already been asked

Finder only provides general advice and factual information, so consider your own circumstances, or seek advice before you decide to act on our content. By submitting a question, you're accepting our Terms of Use, Disclaimer & Privacy Policy and Privacy & Cookies Policy.
Go to site