Hair relaxer: New study by Kao reveals that carbonic acid can enhance the effects of hair styling ingredients

The maker of Kanebo, Sensai and Curél conducted this study to find a more effective way to deliver treatment to hair after chemical treatment and ageing hair.

The Japanese cosmetics company has been focusing on organic acids to establish hair-improving technologies, such as repairing the internal cavities within the hair.

“As an evolution of that technology, we focused on carbonic acid. It has long been known for its blood circulation promoting action through vasodilation,” ​said Kao.

Additionally, the firm knew carbonic acid could act on the keratin on the surface of the stratum corneum to make skin smoother, driving the firm to study its effects on hair.

In one experiment, researchers mixed wool-derived keratin powder with carbonated water and observed that the keratin powder expanded.

This confirmed that carbonated water could promote water retention.

The team hypothesised that the carbon dioxide could be acting on the keratin inside the hair, making it easier for the hair soaked in carbonated water to hold water.

In the next experiment, the researchers wanted to prove that carbonic acid-enhanced water-retention in keratin derived from hair

They infused pTS salt and succinic acid in carbonated and non-carbonated formulations. pTS salt is known to relax hair while succinic acid helps it to penetrate the surface of the hair.

Hair was immersed in both carbonated and non-carbonated formulations for 15 minutes.

The result showed that the stress relaxation rate was significantly higher in the preparation with carbonic acid and that no difference was found in the formula without carbonic acid.

This led the researchers to believe that the combination of carbonic acid and pTS salt enhances the effect of succinic acid.

Furthermore, the researchers used Time-of-flight secondary ion mass spectrometry (ToF-SIMS), an analytical method that can detect inorganic and organic substances on the surface with high sensitivity at the molecular level.

They used it to visualise the cross-section of the hair and found that the distribution of pTS salt inside the hair was higher in the presence of carbonic acid.

“This study suggests that the effect on hair may be enhanced by combining carbonic acid with a component that has a hair-modifying effect. It is speculated that this is because carbonic acid promotes the penetration of the modified component into the hair,” ​said the researchers

Additionally, they concluded that increasing the penetration of pTS salt could improve hair waviness due to the effect of relaxation.

“We believe that applying carbonic acid to hair care is one of the effective means to treat hair that has changed due to chemical treatment or ageing for healthy and beautiful hair. We will continue to study the effects on hair and the mechanism of action of it.”​