Before we go into K18 products, we should first learn about conditioning and protein products.
Hair mainly consists of a tough protein called keratin. Bleaching, heat styling, keratin treatments, etc can damage the keratin. Once the keratin is damaged, it cannot be repaired.
Conditioning agents attach to the outer layer of the hair and smoothen the surface but the inner keratin layers responsible for the strength of the hair are not repaired. These conditioning agents only temporarily attach to the surface and can be removed by the next wash.
Most proteins work like standard conditioning agents. These proteins temporarily attach to the outer layer. Only low molecular weight peptides and amino acids can go into the hair cortex and interact with the damaged keratin.
The protein in our hair is made up of strings of amino acids, but the order of those amino acids is very specific and if you want a peptide (chains of amino acids but smaller chains than protein) to bind to this specific order, you need to study the sequence of the hair keratin and design a peptide that can bind to the hair.
This is how K18 products work, they spent so many years trying to find the perfect combination which has the highest affinity and improves the hair.
K18 vs Olaplex
There are strands of keratin present in our hair. These keratin strands are held together by several types of bonds (disulfide bonds, salt bonds, hydrogen bonds, van der Waals forces). The strongest bond type is disulfide bonds. These are the permanent covalent bonds. Hair colouring, perming, heat styling, hair styling, and UV light can break these disulfide bonds which can result in weak and damaged hair.
Bond builder products like Olapex aim to repair broken disulfide bonds. These bond builder products contain a molecule from which the ends of this molecule bind to the sulfur in the hair keratin., creating an artificial and extended bridge. The bond these molecules make with the sulfur of the hair is mostly ionic bonds. Disulfide bonds are permanent covalent bonds, but covalent bonds are stronger than ionic bonds, and ionic bonds are more likely to be broken when products with a higher alkaline pH (like shampoo) are used.
The artificial bridges can, therefore, wear off faster, and frequent use of the product is needed.
K18 products help at restoring the pillars/foundation of the bridge (the keratin strands). In bond builder products the pillars (keratin strands) are not repaired, as there is only a bridge between the strands. K18 aims at restoring the pillars (keratin strands) and improving the strength of the hair.