Dull, frazzled lengths? A bond repair hair treatment is the answer. From Olaplex to K18, Living Proof to Redken, we put the best bond builders to the test for strong, glossy locks

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The bond hair repair treatment is having a moment. But until Olaplex exploded onto the haircare scene back in 2014, you probably didn't know what a 'hair bond' was. Now we're spoilt for choice when it comes to finding the best deep, restorative hair bond repair treatment, thanks to a string of high-tech new launches from the likes of K18, Redken and Living Proof, which are taking bond repair to new levels, with prevention as well as cure. 

The latest buzz is surrounding Epres, a new bond repair haircare brand just launched by Eric Pressly, the inventor and scientist behind Olaplex. It's a fine concentrated refillable spray, that you spray on at least ten minutes before washing (or overnight).

What are hair bonds and why do they break?

Back to basics - what are hair bonds? Hair is largely made of keratin, and like any protein, it's composed of amino acids, which are joined together by bonds. "Think of hair bonds as the scaffolding that runs right through the middle of the hair shaft and makes up the strength and elasticity of your hair," says Michael Shaun Corby, global creative director of Living Proof. "These bonds are connected in different ways, some horizontally, some vertically."

There are three main types of bonds: hydrogen bonds, ionic (or salt) bonds and disulphide (or covalent) bonds. Still with us? They all behave differently when your hair is exposed to humidity, heat and stress. 

What are hydrogen bonds and ionic bonds 

The first two break quite easily with moisture and then reform – the reason why your hair shape looks different (say, less curly) when it's wet than when it's dry.

 It's also the reason why your hair becomes more fragile when it's wet and many stylists recommend wrapping it in the best hair towel you can get your hands on and gently squeezing rather than rubbing it after you've washed it. 

"Hydrogen bonds are the weakest type of bond, they break down easily with humidity," says Corby. This is why your hair loses its style or goes frizzy when it's humid and a humidity-proofing hair product is your friend. They reform again when the hair is dry, which is how you can 'set' your hair with heat in your chosen style. "They're like the little worker bees holding everything together and there are lots of them," he says.

"Ionic [or salt] bonds are stronger but they still break down when the hair is completely wet. Both hydrogen and ionic bonds break and reform all the time."

What are disulphide bonds?

Disulphide bonds, on the other hand, break permanently under stress from factors such as heat, colouring or tugging and these are the ones that bond builders primarily target.

"They are the strongest, are more brittle and don't naturally repair themselves, " says Corby. These are the ones that when they break, make your hair look frazzled, dry and hard to style. You need a bond-building treatment to repair them - some newer bond builders such as Living Proof Triple Bond Repair also work to strengthen these to help prevent them from breaking in the first place. Others, such as Olaplex, work to repair broken bonds, making it suitable for hair that has already been damaged rather than as a protective step.

Who needs a bond repair treatment?

Everything from colouring to heat styling to brushing and environmental aggressors such as pollution can cause disulphide bonds to break, so if your hair looks a little lacklustre, dry or extra frizzy, chances are you’ve got some damaged hair bonds. You can’t actually see broken bonds, as they occur in the inner layer of the hair, stylist and colour expert  Samantha Cusick, whose eponymous hair salons are in London's Notting Hill and Fitzrovia tells us that dry, damaged or chemically-treated hair more than likely has bonds that have been broken, showing themselves as coarse, dry, frizzy hair that breaks easily.

Unlike conditioners that coat and hydrate strands, bond repair hair treatments work to heal and strengthen the shaft from within, working on one or more types of bonds, depending on your product.

How often should I use a hair bond repair treatment?

This depends on the condition of your hair and the product instructions.  “If you have hair that is weak and prone to breakage, or you do a lot of heat styling, you should try to use a bond-maintaining shampoo and conditioner every time you wash, plus a deeper reparative treatment once a week,” says Cusick. “If your hair is generally healthy and you just want to make sure it stays that way, weekly bond-building masks are great for this.”

Be careful not to over-use a hair bond repair treatment

While home bond builders are a boon, especially for repairing bleach- and heat-damaged disulphide bonds, they can be used incorrectly or even needlessly, so top stylists tell us. Colourist and co-owner of Four London Charlie Double offers both K18 and Olaplex as basin treatments to her clients and says that while Olaplex has its place for truly damaged hair, she finds that many clients are over-using the at-home treatment, often when their hair isn't damaged enough to need it. "I can tell because their hair becomes very brittle. For those people, I prefer K18,” she says.

Meanwhile, stylist Adam Reed, founder of Arkive Haircare prefers an approach that looks after the hair so it doesn’t become damaged enough to need a pricey disulphide bond builder. “You only need one if you’ve broken the bonds in your hair by using bleach,” he says. “You shouldn’t encourage your hair to need the bonds to be fixed – don’t let it get that bad!”

However, he does rate Living Proof's new Triple Bond Repair and K18 as smoothing and styling treatments.

How long do bond repair hair treatments take to work?

The good news is they get to work right away. Each time you use bond-repairing hair care, the condition of your hair improves, says Redken educator Jack Cunningham-Rose.

Each product has its own treatment time. Olaplex at-home haircare products typically take ten minutes for the bond-building tech to work its magic, with others such as K18 it's just four. Living Proof's new Triple Bond Complex requires ten minutes after your conditioner step to work and then needs to be activated by a shot of minimum 60C heat to activate the healing technology.

We've tested some of the best bond repair hair treatments for coloured and heat-damaged hair (and, by the way, our locks have never looked or felt stronger).

Best for coloured hair: Epres Bond Repair Treatment, £46

The unique thing about Epres is that the formula is acid-free. Nearly all other bond repair treatments change the pH levels of the hair to make the internal keratin bonds reform. The problem, and the irony of that, is if you overload the hair with too much acid it can cause hair to break, which is the exact opposite of what you want from a bond-repairing treatment. The creator of this, who interestingly was the original scientific brain behind Olaplex, has managed to create a pH-neutral formula that is really lightweight and can sink into the hair instantly making it ideal for coloured hair. It also keeps working once the hair is dry and the brand say after just one use you will see visible difference in the condition of your hair. And when we tried it our hair was so much easier to blow-dry afterwards and undoubtedly less frizzy. 

In terms of how you use it, it’s very simple - arguably the most simple of all the bond repair treatments out there. You pour the concentrated solution into the bottle (that it comes with), fill it with water to the marked line, shake it up and then spray it all over dry hair. Then wait around ten minutes and shampoo as normal. You may find you can skip conditioning as your hair will feel soft enough.

It's gentle enough to be used every week and you are meant to saturate the hair with the product so longer and thicker hair will empty the spray in one treatment. Short and finer hair may only need half.

Best for all hair types (even hair that isn't badly damaged): Living Proof Triple Bond Complex 45ml, £42

Living Proof's Triple Bond Complex contains technology that the brand claims can strengthen, reform and even create brand new bonds of all three types, making your hair up to eight times stronger (they've stress-tested it in the lab against their biggest competitors, which snapped sooner). "Other bond-builders can repair covalent [disulfide] bonds, but it usually requires them to be damaged in the first place, whereas we don't. That's why we call it 'future-proofing your hair,'" Corby says.

Most bond-building products repair bonds in either one direction (vertical or horizontal), he says, while Triple Bond Complex repairs in all directions. The result is hair that is stronger, softer, smoother and more resilient to damage, they say. It also helps hold your style for longer (because the hydrogen bonds break less easily). After one treatment, we noticed that our hair felt and looked thicker and stronger, and our beach waves lasted well into the next day

Apply two pumps (and up to six) to damp hair after your conditioner step, wait ten minutes, then dry your hair as normal. Best results are achieved through activating the treatment with 60C heat. A simple quick shot of heat is fine, so if you normally air dry blast it when the hair is wet and leave it to drip dry as normal, that's fine, too.

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Best for convenience: K18 Leave-in Molecular Repair Hair Mask, £12-£70

When K18 launched in the UK  it was immediately dubbed 'the new Olaplex' by beauty editors. K18's bond-repairing treatment features a patented peptide that mimics keratin chains found in the hair shaft (which are the vertical lengths of the hair shaft ladder) and repairs horizontal disulfide bonds along the way. The brand inspected thousands of sequences of amino acids in the hair to find the formula. This is possibly the most straightforward bond repair hair treatment we've used and it goes in place of your conditioner and styling cream. Simply shampoo your hair and gently towel dry. Apply two small pumps - a little goes a long way, good job as it's not cheap - then leave on for four minutes and you're good to go, whether that's following with heat styling or leaving your hair to air dry.

Our tester noticed that her hair appeared fuller, the ends less split and, surprisingly for a leave-in product, it left no greasy residue. Both K18 and Living Proof's treatments are travel-friendly sizes, too.

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Redken's best-selling (and now TikTok famous) Acidic Bonding line launched with a shampoo, conditioner and leave-in treatment, all designed to target weakened bonds of processed hair. Now, it has followed up with this Intensive Pre-Treatment, which you could say is a rival to Olaplex's now-cult No.3 Hair Perfector.

The range contains Redken's Bonding Care Complex, plus citric acid, an alpha hydroxy acid (AHA), which helps reinforce weakened bonds - and this pre-treatment features the highest concentration of any of the products in the range. The entire range smells like salon haircare and our tester found it made her hair smoother, bouncier and more elastic after one use. 

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Best bond repair with conditioner: Olaplex No.8 Bond Intense Moisture Mask, £22.40

You're probably already aware of the now cult Olaplex No.3 pre-treatment, the OG hair bond repair treatment, but Olaplex No.8 Bond Intense Moisture Mask is fast converting beauty editors and is a good option if you prefer a post-wash 'mask' to a pre-treatment.  Our tester applied this the first time she washed her hair post-bleach and was impressed by how easily it soothed her distressed hair, which normally tangles like a bird's nest post-colour. It works to reinforce fragile bonds to make the hair look smooth and shiny, with avocado and hemp oil to nourish. You need to leave it on for ten minutes for it to get to work, so not one to use if you’re in a rush. Samantha Cusick suggests using this to maintain freshly coloured hair from home, or to top up hair that’s had an Olaplex treatment in salon. It’s a fairly thick mask and it soothes the hair cuticle for that smoothed look, but it doesn’t feel heavy on the hair.

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Best budget hair bond treatment:  The Inkey List PCA Bond Repair Hair Treatment, £13.99

Just like all of  The Inkey List’s hair care, this is pleasingly affordable and just as high performing as you’d expect from the brand. It's preventative as well as repairing. PCA stands for pyrrolidone carboxylic acid, a very small silicone. The brand says. don't panic, it's non-irritating. It’s a lightweight leave-in mist that helps to strengthen and rebuild all three types of bonds, improving shine and helping prevent split ends. Our tester reports that you need about ten sprays if you have shoulder-length hair, and while the nozzle is a bit stiff and difficult to use, it’s well worth it in terms of manageability and smoothness.

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Best vegan and heat-protecting hair bond repair treatment:  Aveda Botanical Repair Strengthening Leave-In Treatment, £28

This took six years in the making and is designed to strengthen and repair damaged hair bonds, although it doesn't specify whether it acts on disulfide bonds, which are the ones that don't repair without help.  What it does offer is protection to help stop them breaking in the first place and is a convenient leave-in gel-cream that heat protects up to 230 degrees and provides UV protection too.  It mimics the outer lipid layer of the hair to create a protective shield that makes the hair five times stronger but is lightweight and undetectable when you apply it. Apply to damp hair as you would a blow-dry cream and it melts in. Our tester found her hair was instantly smoothed but did find herself using a lot as it’s lightweight.

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Best trichologist-formulated hair bond repair treatment:  Philip Kingsley Bond Builder Restructuring Treatment,  £28

Trichologist brand Philip Kingsley has three products under their  'Bond Builder' umbrella (all of them excellent) but it's this pre-wash mask that you apply to dampened hair, that actively protects existing bonds and repairs broken bonds. Leave on for ten minutes before you wash. Our tester loved the softness of her hair after using this cream which has moisturising panthenol. If you have damaged hair it's worth checking out the other two products in the range. The Philip Kingsley Bond Builder Split End Remedy, £26 was a winner with our tester's overly-styled and coloured fringe. This worked like magic to fuse the damaged ends and the hair look make less brittle, without appearing greasy. The excellent Bond Repair Lipid Shield Oil, £29 is a heat-protecting ultra-light smoothing oil that gave our tester the best blow dry ever.  

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