K18 hair mask

“I tried the genius K18 leave-in hair mask Hailey Bieber swears by, and here are my honest thoughts”

Posted by for Hair

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A no-rinse treatment, the mask replaces conditioner in your hair routine.

The volume of hair masks I’ve tried in my lifetime likely numbers in the hundreds. Initially, each one promised to transform/revive/rehydrate/soften (delete as applicable) my heat and colour-damaged hair. While many came close, a sudden change in weather, hormones or the way I chose to style my hair rendered them too heavy, too late or simply not effective enough. So, when I saw the K18 hair mask launch in the UK at Cult Beauty last month, I knew I had to try it. This hair mask has a long scientific rap sheet and is loved by celebrities (Hailey Bieber, Rihanna and Selena Gomez are all reported to be fans) and their incredibly talented hairstylists. 

An innovative formula that doesn’t require rinsing, the K18 Leave-In Molecular Repair Hair Mask is suitable for all hair types (1a to 4c) – the only thing that changes between hair length and texture is the amount of product that is used.  

So, how did the cult hair mask fare under my beady beauty eye? Read on for my full K18 hair mask review, as well as a full explanation of how the mask works and how often to use it. 

What is the K18 hair treatment?

At its base level, the K18 mask is a whole lot of science in one little bottle. Unlike bond-building treatments that repair broken disulphide bonds along the width of the hair, the K18 treatment repairs the hair’s core structure along the length and width of the hair.

The K18 Peptide (a patented molecule) is a unique bioactive peptide that repairs broken polypeptide (keratin) chains caused by bleach, colour, chemical services and heat. 

Championed with reversing the signs of damage and improving the strength, softness, smoothness and elasticity of the hair, the mask is applied to freshly washed and towel-dried hair and left for four minutes to “activate”. After the four minutes are up, you’re set to style and treat your hair as you would normally post-washing – no rinse necessary. 

Does the K18 hair mask help with hair growth?

Concerned more with treating hair damage than downward trajectory, the K18 hair mask is not a “growth” treatment per se. However, hair that has unaddressed damage won’t grow well. Repairing your hair using the mask could mean your hair is able to grow faster and more regularly. 

Rely on it for repairing the hair you do have, not for the hair that’s yet to come. A scalp scrub, scalp oil and scalp massager are all good add-ons to encourage healthy hair growth, too.

How often can you use the K18 hair mask?

At the beginning of your K18 journey, it’s suggested that you use consecutively for four to six washes. Then, after you’ve completed that cycle, dial down to once every three to four washes. 

Remember, the routine goes: shampoo, towel dry, K18 hair mask, a four minute wait and then any of your usual styling rituals. You shouldn’t be applying a conditioner over the top or rinsing out the K18 hair mask. Trust the process. 

Is the K18 hair mask worth it?

And now for the bit you’ve been waiting for. What was the K18 hair mask actually like to use?

First of all, it was novel to shampoo, towel dry and go. While I normally wring out excess water from my hair before applying a hair mask (it helps product more effectively penetrate the hair shaft), I usually have to waste 10–15 minutes in the bath while a wash-out hair mask does its work. The K18 hair mask was speedy and slick; I was in and out in half the time. 

Using the handy dosage guide, I applied two pumps of product through my “long and fine” hair. It didn’t feel like nearly enough product (I’m not a “pea-size” type of person) but I knew I had to leave it to do its thing. 

K18 Hair Treatment Mask Review

Following up with heat protector, a comb through and a speedy blow-dry, my hair was soft and shiny – not lank or limp as I had feared. The mask saved me time, effort and did the same job as many of my wash-out masks. 

However, at £25 for 15ml and £55 for 50ml, it’s not a cheap option. When you consider the Olaplex No.8 Bond Intense Moisture Mask is £26 for 100ml, the difference in relative price per use is definitely something to consider. While they perform different functions (the K18 treatment isn’t washed out whereas the Olaplex mask is), everyone’s budget is individual.

Personally, I think the K18 hair mask is a genius product. It’s efficient and effective, and my colour and heat-damaged low-porosity hair drank it up. In future, I’ll focus the product more towards the mid-to-ends of my hair and much less near the root. It wasn’t that I had used too much product, more that I had been too judicious in applying it evenly to my head regardless of where the majority of the damage is. 

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