No matter your hair type, damage is part of the daily grind. Whether it’s from brushing, blow-drying, highlights or UV exposure, aggressors take a toll on our strands, and we need help to repair them. In 2014, a lab sample of what we now know as Olaplex’s No. 3 hair perfector landed in the hands of celebrity colorist Tracey Cunningham, and it changed the brand’s future, and also the hair-care industry as a whole. The formula quickly became a salon staple to make color services less damaging, and today, it’s the best-selling hair-care product on Sephora’s shelves. Though it’s been eight years, the bond-repair category is booming, and more brands are entering the space now than ever before.
According to beauty trend tracker Spate, products that strengthen and repair damaged hair are among the top Google searches in the hair category, alongside thinning hair and hair loss. And unlike our skin, which possesses certain intrinsic repair properties, our hair is essentially dead protein, which means it requires a helping hand to repair damage. As every hairstylist and colorist I’ve ever interviewed would agree, if you have damaged hair and you use a good bond-building product, you will see and feel a difference.
What are bonds?
Our hair is mainly made of keratin (protein), which comprises two strands of amino acids, and these strands are linked by bonds. Think of keratin like a ladder, and the bonds are the steps, held together by the sides, or the amino acid chains. “Hair bonds are responsible for the structure and strength of hair,” says hairstylist Alifia Young, education development manager for K18. Celebrity colorist Chad Kenyon explains that bonds can become damaged by high heat from styling tools, such as flat irons, curling irons and blowdryers, as well as brushes, especially if you brush your hair when it’s wet. “This can result in frizz, split ends, dryness and dull color.” The weather can also impact hair bonds, as sun exposure, humidity and pollution all play a negative role.
The 3 Main Types of Bonds
There are three primary bonds that make up the structure of the hair, and when these bonds break, damage ensues.
“These are temporary bonds and the weakest of the three types,” explains Melissa Sullivan, director of marketing for Living Proof. “They are easily broken when water or heat are present, like how hair gets frizzy in high humidity.”
Salt bonds (aka ionic bonds), are also temporary like hydrogen bonds. “They are stronger than hydrogen bonds, but can break when the hair is wet or exposed to a change in pH,” Sullivan says. “Though temporary, both ionic and hydrogen bonds contribute to the hair’s overall strength and elasticity.”
Covalent (Peptide and Disulfide Bonds):
“The polypeptide bonds in the keratin chain and the disulfide bonds are essential for strong and resilient hair,” says Young. “When these bonds are broken from aggressors, the hair can become fragile, and you may notice the hair not retaining length due to breakage.” Sullivan adds that these bonds are strong and permanent, and will stay whether the hair is wet or dry, but they can be damaged by hot styling tools, bleach and chemical treatments like color services and relaxers. Maintaining covalent bonds contributes to the hair’s shape, appearance and overall health.
Did You Know? Some bond products can also be used on human hair extensions, but it’s best to do a strand test beforehand because if the hair has a keratin coating, the bond product won’t penetrate.
How Bond Products Work
Bond-repair products go beyond deep conditioners to mend broken bonds and make hair stronger. “Most bond builders focus on building hydrogen or ionic bonds, but very few create covalent bonds,” Sullivan explains, noting that it’s important to research the ingredients in a product before choosing one for your hair. According to cosmetic chemist Ginger King, the majority of key ingredients in bond builders are amino acids, “especially to build the cysteine disulfide linkage for repair. However, not all products work the same way: Some, like Olaplex and K18 are legit when it comes to chemical bonding, while many others, like those that only target hydrogen bonds, merely mend the hair temporarily.”
At-home bond treatments are typically designed for weekly use, and using them more often—or applying too much—isn’t better. Though Kim Kardashian and some TikTokers have advertised sleeping in these types of products, it’s not necessary for optimal results and you don’t want them to get on your face or in your eyes, so it’s better not to risk it.
In the salon, stylists swear by these products for “healthier” coloring, i.e. less damage. “This is especially true for blondes and anyone going lighter than their natural color because bleach breaks bonds,” says Kenyon. “I use Olaplex, which can be mixed into all colors and lighteners, and then there’s a post-color process, but the whole thing only takes about 30 minutes. Everyone can benefit from using a bond builder, whether you have curly, straight, chemically compromised or virgin hair, or something in between.”
These five bond products reign supreme when it comes to total hair transformations with results you can see and feel.
Olaplex No.3 Hair Perfector ($30)
The OG in this category, one of these little bottles sells every 3.5 seconds around the world. “Our patented ingredient, bis-aminopropyl diglycol dimaleate, works on a molecular level to repair broken disulfide bonds and restore damaged hair from the inside out,” says Lavinia Popescu, chief scientist of R&D for Olaplex. “It dramatically improves the strength of the hair—it works on all hair types—and that impacts how it feels.” Apply it from root to tip on damp strands—if you have a lot of dry shampoo in your hair, consider shampooing beforehand so Olaplex can effectively penetrate—leave it on for 10 minutes, and then rinse it out really well and shampoo as usual.
K18 Leave-In Molecular Repair Mask ($75)
K18, a biomimetic peptide—it’s also the brand name—took the hair-care world by storm in 2020 when it forged an entirely new category in the bond space. “Our K18 Mask works on the innermost layers of the hair to restore broken keratin chains and the disulfide bonds, reversing damage and improving strength and elasticity in just four minutes,” says Young. “This was a game-changer for me as a stylist, and in my personal routine. Use it for about four to six shampoos—we call this the repair phase. Then, about every third shampoo when you need a refresh. It’s also great to use after salon visits to protect your hair color investments.”
epres Bond Repair Hair Treatment Kit ($48)
New to the scene is this patented innovation, which was created by chemist Dr. Eric Pressly, who holds more than 100 patents in bond-repair technology. Made for all hair types, it actively rebonds the hair’s structure using a unique lipid-molecule technology that diffuses repair benefits throughout each strand for hours after it’s applied. “The Kit comes with a concentrate that you mix with water in the accompanying refillable spray bottle,” says celebrity hairstylist Bradley Leake. “Spray it on, let it sit for at least 10 minutes, and then wash your hair and style as normal.” Use it once or twice a week to get your hair back into shape, and then weekly to maintain the results.
Redken Acidic Bonding Concentrate Leave-In Treatment ($30)
This leave-in treatment features a “bonding care complex that works on the outer layer of the hair, and citric acid, which penetrates the fiber at a molecular level to effectively capture metal ions and reinforce weakened bonds in the hair,” says Christina Bishop, director of scientific valorization at L’Oréal. “Together, this helps protect the hair’s strength and leaves the hair more resistant to breakage.” Apply a dime-size amount to clean, damp hair (longer and/or thicker hair types may need more) and leave it in.
Living Proof Triple Bond Complex ($45)
“We recently launched our most scientifically advanced innovation, which targets all three types of bonds to improve the hair’s core strength from the inside out,” says Sullivan. “This weekly treatment uses patentpending technology to create a 3-D network in the hair fiber, resulting in hair that’s eight times stronger. It reduces visible signs of damage and also protects against future damage. It provides heat protection up to 450 degrees, too.” Apply it on clean, damp hair and let it sit for at least 10 minutes before blow-drying and styling.
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