What sun, salt, and chlorine do to colour-treated hair

Every summer we see the same pattern: clients come in after a holiday with colour that has shifted in ways they did not expect. The brassiness, the dullness, the unexpected warmth at the mid-length. Most of it is predictable once you understand what is happening at the level of the hair shaft.

UV light and oxidation ¶

UV radiation oxidises melanin, both natural and artificial. For lighter colours, this means warmth creeps back in, particularly at the ends where the hair is most porous. For darker colours, UV can produce a reddish or orange cast that was not there in spring.

The effect is cumulative. A week in the sun is manageable. Six weeks of daily UV exposure without any protection will shift most colour noticeably. A UV-filter leave-in product applied before sun exposure is the most practical defence. We stock one in the salon and include it as a rinse in our late-summer gloss appointments through September.

Chlorine: the specific risk for copper and blonde tones ¶

Chlorine strips the cuticle and, in high concentrations, can react with residual copper-based pigments in the hair to produce a greenish tint. This is more common than most people realise, particularly in hair that has been lightened and toned with a cool or ash formula.

The practical fix is simple: wet the hair with fresh water before getting into a chlorinated pool. Saturated hair absorbs less chlorine than dry hair. Rinsing immediately after swimming and applying a small amount of conditioner to the mid-lengths before you go in both reduce the effect significantly.

Salt water and the cuticle ¶

Salt water is less aggressive than chlorine but still drying. The main issue is that it raises the cuticle, which makes colour look duller and feel rougher. The colour itself is not being stripped, but the surface of the hair is not reflecting light cleanly.

A gloss treatment in late August or early September resets the tone and closes the cuticle. It takes thirty minutes and costs from ¥8,550. It is the most efficient way to bring the colour back to where it was before the summer.

None of this means you should avoid the sea or the pool. It means a small amount of preparation and a gloss appointment at the end of August will keep the colour looking like you paid for it.