Let’s run with the presumption that you’ve all heard of Olaplex! The three-step treatment has been around now for nearly a decade so there’s a good chance that, unless you’ve been living under a rock, you’ve either read about it, have tried it or are a devotee.

It would be fair to say that the arrival of Olaplex revolutionised hair care. Initially only available in-salon, the ground-breaking treatment took the industry by storm and instigated a flood of other bond-repair products onto the marketplace. Yet few have been able to compete with the cult favourite. The introduction of Olaplex’s first at-home treatment, the No. 3 Hair Perfector, further secured the company’s top ranking position and took the brand stratospheric –  a bottle of No 3 being sold every 3.5 seconds*.     

It appeared that Olaplex had the market cornered, leaving little space for yet another new competitor. Until now… 

The new kid on the block, K18, is a revolutionary treatment that some of you might not be as familiar with. Launched into the UK in 2022, it’s Leave-In Molecular Hair Repair Mask has gained a number of fans on Tik Tok - Rihanna and Hayley Bieber being two of its greatest supporters. Similar to Olaplex, there is a lot of science behind the brand, the company drawing on 10 years of research to develop a bioactive peptide capable of penetrating the innermost layer of each hair fibre.

As hairdressers, the question we are most commonly asked is ‘so what’s the difference between them?’ 

Whilst they may appear to be similar treatments and have similar goals, they are in fact very different in their approach to tackling hair damage. Before we delve into how each one works, let’s take a closer look at the overall structure of a typical hair fibre and the external factors that affect it.      

Overall Structure Of A Hair Fibre

The section of a hair fibre that is visible above the skin, is called the shaft and formed of three layers, the cuticle, the cortex and the medulla.

The Cuticle – forms the outermost layer of the hair. This is where shampoos and conditioners work at a surface level, to produce superficial hydration and sheen. 

The Cortex – this is just below the surface of the outermost layer of the hair where Olaplex (and other disulfide bond repair treatments) work. Contained within this are the:

  • Cortical cells – contained within the cortex
  • Macrofibril – contained within the cortical cell
  • Intermediate filament – contained within the macrofibril
  • Polypeptide chains – contained within the intermediate filament. This is where the K18 Peptide works to reconnect broken polypeptide chains

The Medulla – the deepest layer of the hair shaft, only found in large and thick hairs. 

What Are The Factors That Cause Damage To A Hair Fibre? 

There are a number of external factors that can create havoc with even the healthiest of hair, including: 

  • Thermal factors – high levels of heat from hairdryers, irons and hot tools  
  • Mechanical damage – brushing, friction from hairbands and bobbles, tugging or pulling on wet hair  
  • Chemical services – bleaching, colouring, relaxing treatments, perms etc 
  • Environmental damage – UV damage from the sun, extreme heat or cold weather conditions, humidity and pollution  

What Happens When The Hair Fibre Becomes Damaged?

All hair types, whether curly, fine or straight etc, contain millions of disulfide bonds which hold the proteins in the hair shaft together, providing strength and elasticity to the hair. When properly paired, these bonds give hair its overall structure, strength and stability resulting in healthy and shiny hair.  

Unfortunately, any of the factors listed above can adversely affect these disulfide bonds, causing them to break apart and lose protein. 

Here’s the science bit... 

At this point, one of two reactions can take place:

  1. The single sulfur hydrogen molecule (from the broken disulfide bond) pairs with a single oxygen molecule, thus re-creating a perfect pair


  1. The single sulfur hydrogen molecule pairs with three oxygen molecules, creating a sulfate group. This protonated sulfate or cysteic acid as it is known then eats the protein out of the hair resulting in hair damage 

The outcome – split ends, thinning, dryness, frizz, lacklustre colour ….. take your pick! If you’re really lucky, you may even get a combination of a few. 

As mentioned earlier, traditional shampoos and conditioners only work at a superficial level to add temporary moisture and sheen. If you want to repair your damaged locks, you’re going to need the added value of science.

How Does Olaplex Work?

Olaplex restores damaged and compromised hair by repairing from the inside out through use of its patented single ingredient, Bis-Aminopropyl Diglycol Dimaleate. When damage has occurred, the ingredient penetrates the hair shaft to pair with the single sulfur hydrogen bond at a faster rate than the three oxygen molecules, recreating the disulfide bond. The result, stronger and healthier hair.   

It can be used in conjunction with hair colouring services to minimise chemical harm and maintain the integrity of the hair, improving health and overall appearance.

The treatment is a three-step process. Step one involves the application of a bonding agent that penetrates the hair shaft to repair broken bonds in the hair. Step two consists of the application of a bonding cream that further strengthens and protects hair with step three being the at-home treatment, that can be used between visits to maintain and extend the results produced in-salon.   

How Does K18 (Biomimetic Hairscience) Work?  

Put simply, biomimetics is the practice of learning from and mimicking nature. 

K18’s patented hair care technology contains a bioactive peptide that penetrates the hair shaft to reach the innermost layer of the hair fibre. 

The company spent over a decade in studies, mapping out and testing all of the decapeptide sequences that are expressed in the human keratin genome. They discovered one unique sequence that was capable of reconnecting the broken polypeptide chains (found within the cortex) and mimicked this natural structure of keratin amino acid sequences to produce the K18 bioactive peptide™. 

Recognised as natural by the hair, the peptide is the perfect size and shape to repair the innermost layer of the hair fibre, reconnecting broken keratin chains that form the building blocks of hair, to restore the hair’s natural structure and renew strength and elasticity. As a result, this also reconnects the disulfide bonds, which Olaplex tackles.

The process helps to protect hair from future damage reducing the risk of breakage and split ends. After just one salon treatment hair is restored to 91% of its original strength and 94% of its original elasticity.**  

Unlike other treatments, K18 works in just 4 minutes. It’s no fuss approach is an absolute winner as you simply apply and leave in, with no rinse required. Most leave-in products can leave hair feeling weighed down and greasy, but this is simply not the case with K18, even on finer hair.

So, Which Is Best? Olaplex Or K18?

Both Olaplex and K18 are extremely effective hair care technologies that help to repair and strengthen hair that has been damaged by a variety of causes including chemical processes, thermal factors, mechanical and environmental damage. As demonstrated above they work in different ways yet both will improve hair texture, reduce frizz and enhance the colour retention and overall manageability of all hair types.  

Bond builders, such as Olaplex relink the broken disulfide bonds in the outer layer of the cortex, whereas K18 claims to deal with the entire cortex. It starts by reconnecting the broken polypeptide (keratin) chains before then also tackling the disulfide bonds. The result? According to Jordan Alexander, senior director of global sales and education at K18, ‘stronger, shinier, and more resilient strands’.   

Is one product better than the other? That is really up to you, the consumer, to decide. Having used both products in salon, we’ve seen first-hand the difference these treatments can make to damaged hair. 

Anyone who is already a fan, will have noticed the benefits so won’t necessarily feel the need to try out a different brand however if you’ve not road-tested either of these hair care technologies before, they’re definitely worth the investment. 

In the case of Olaplex versus K18, in our opinion, they’re both winners. After all, who doesn’t want healthy, shiny and more manageable hair?!


** Source K18

Joseph Ferraro Hair (JFH) Ltd is a team of professional stylists that deliver exceptional hairdressing services for the individual. Owned and founded by Authentic Beauty Concept Ambassador and North Eastern Hairdresser of the Year (2016), Joseph Ferraro, the JFH team is dedicated to providing expert hair care. 

Should you need further information or advice on our range of products or wish to speak to a member of the team, please email