Bond Building Myth Busting

Bond-building has become the buzzword in hair care. Once limited to salons, the introduction of bond-building products to retail stores enables consumers to experience their transformative effects at home. However, despite being one of the fastest-growing claims in haircare, bond-building remains poorly understood by both consumers and professionals. 

With so many myths surrounding bond building and hair repair, it can be tough to distinguish fact from fiction. That’s why I’ve assembled a team of hair care experts to answer your questions and debunk some of the most common misconceptions about bond builders. 

Helene: Before diving into the myths, let's start by answering the question: What are bond builders? 

Paul: There is no standard scientific definition of a bond builder. In collaboration with Jennifer Marsh, Ph.D., of Procter & Gamble, we proposed it should be defined as a "formulation component that penetrates the hair and improves or restores its internal structure, enhancing mechanical properties." You can read the article here. This allows for both single molecules and blends, without restricting the definition to specific types of molecules or bonds. The focus is on internal effects, not surface action, and applies to both damaged and healthy hair. Crucially, the improvement must be measurable, not just perceptible, ensuring a scientifically valid impact.  

Helene: Do bond building products target just one type of bond? 

Mike: Bond builders found on the market target various types of bonds within hair, which is primarily composed of keratin protein. Keratin, like all proteins, is made of amino acids connected by strong covalent peptide bonds, forming the structural backbone of hair.   

One key amino acid in keratin is cystine, which forms strong disulfide bonds, crucial for hair's strength. These disulfide bonds are permanent and can only be broken by harsh chemicals like bleach, which may damage hair by breaking other bonds and depleting essential proteins, lipids, and oils, leading to weaker, brittle hair.  

In addition to disulfide bonds, hair has weaker, temporary bonds, such as hydrogen bonds and ionic (salt) links, formed by interactions between amino acid side groups. These bonds contribute to hair's mechanical strength and can be easily broken and reformed through heat, water, or changes in pH. For example, thermal straighteners temporarily break hydrogen bonds to reshape hair. However, in humid environments, the reforming of these bonds can cause frizziness. 

Helene: Can bond building products fix split ends? 

Stephanie: The best way to repair split ends is with a sealant like Crodabond CSN™. However, bond builders do strengthen hair, helping to prevent future split ends from forming. 

Helene: Are bond builders only for severely damaged hair? 

Stephanie: While bond builders are primarily targeted at highly damaged hair to over-processed hair (such as bleached or coloured hair), they are suitable for all hair types, regardless of damage level. The difference lies in the frequency of application, with less damaged hair requiring less frequent use. I see great interest in key hair targets such as textured hair (very fragile) and aging hair (thinning) for whom this type of treatment would be a real game changer in their routine and in terms of results. 

Helene: Are bond builders a relatively quick fix for damaged hair? 

Stephanie: Bond building repair treatments can significantly improve hair health but it’s important to note that they are not a quick fix for severely damaged hair. It may take multiple treatments over time to significantly improve the hair’s integrity. The severity of the damage, the hair type, and the frequency of use will determine the number of treatments needed. Regular use of bond building treatments, combined with proper hair care practices, can gradually strengthen and improve the overall condition of the hair. 

Helene: Is there a different between mass market and professional bond builders? 

Mike: The professional bond building market is currently dominated by Olaplex and K18 so I will first explain how these products work. Olaplex uses bis-aminopropyl diglycol dimaleate as the key bond building active. The maleic acid component is claimed to interact with the hair's amino acids, specifically between reduced cystine disulphide bonds, though other mechanisms are possible through potentially influencing pH and salt-link formation. K18 employs a small peptide that penetrates the hair and is claimed to interact with other proteins within the hair, forming hydrogen and disulfide bonds. While the specific peptide sequence is still confidential, K18's development is backed by published scientific research. Both Olaplex and K18 offer promising solutions for damaged hair and while their mechanisms of action differ, both products have demonstrated positive results in consumer trials. 

Mass market hair care products often rely on repairing hydrogen bonds which are weaker, and easier to disrupt. Common ingredients used include hydrolysed proteins, amino acids, and sugar-based molecules, which possess abundant hydrogen bonding sites. More advanced formulations go beyond hydrogen bonds, incorporating materials with enhanced properties. For instance, Keravis™, a modified vegetable protein based on upcycled potato protein, combines hydrogen bonding with cross-linking within the hair fibre. This dual action not only improves hair elasticity and reduces brittleness, but also provides a protective barrier on the surface. By introducing additional bonds between protein chains, modified ingredients like Keravis can enhance the overall integrity and resilience of damaged hair. 

Helene: Is it possible to measure bond repair within the hair? 

Paul:  Yes, absolutely, and when making claims about bond building in hair care products, it is vital to back them up with scientific tests. At TRI, we use three key types of tests: fibre penetration, mechanical properties, and measurement of bond changes. 

The first test involves fibre penetration. For small molecules with unique spectroscopic features, we can perform imaging spectroscopy to observe how the active ingredient penetrates hair fibres. This can be done using hair cross-sections or optical sectioning with a confocal Raman microscope. 

For proteins or lipids already present in hair, fluorescence microscopy can be used to tag and track the material. If these methods don’t work, mass spectrometry imaging (TOFSIMS) can analyse molecular penetration pixel by pixel. 

The second type of test examines mechanical properties, particularly through fatigue testing, where hair is repeatedly stretched to simulate brushing and combing. Bond builders can extend the time before hair breaks. We can also conduct tensile tests, measuring how much force is needed to break the hair. 

Finally, to understand bond formation, thermal analysis (DSC) and spectroscopy (FTIR/Raman) are used to assess how cross-linking impacts the hair's structure. With confocal Raman microscopy, we can even analyse disulfide bonds. These methods provide robust evidence for bond building performance in hair care products.

Helene: At Croda Beauty, our mission is to share science-backed insights and develop innovative ingredients with proven results. Stay updated on our latest research and bond building solutions by joining our mailing list. For even deeper expert insights, access our on-demand webinar, Unlocking the secrets of the bond builder market.