Hair

Chelation — the ingredient you never see, without which the rest does not work

10 September 2026

On an INCI list it usually sits in the second half, at a low level, with an unpronounceable name. Nobody advertises it. In hard water it decides whether the rest of the formula will work.

The problem: tap water is not a neutral solvent

Mains water holds dissolved ions — mainly calcium (Ca²⁺) and magnesium (Mg²⁺), plus copper and iron, much of it from building pipework. Those ions are not passive passengers. They react.

With anionic surfactants they form insoluble salts — the same phenomenon we call limescale in a washing machine and deposit on a tap. On hair and scalp a layer builds that will not rinse, because it is not water-soluble. A film appears: rough, dull, weighing hair down.

The practical effect anyone who has moved to London or Copenhagen knows: hair washed with the same shampoo suddenly feels heavy, dull, harder to style and oilier faster. The shampoo did not change. The water did.

With transition metals it is worse. Copper and iron catalyse free-radical reactions. Copper depositing in keratin speeds its degradation, and in contact with hydrogen peroxide during bleaching it increases fibre damage. Blonde, grey and porous hair accumulates metals most — hence the characteristic green or rusty casts.

The solution: a molecule that grips ions

A chelator (from Greek chele — claw) binds a metal ion at several points at once, locking it in a stable complex. The bound ion stops reacting — it does not form salts with surfactants, it does not catalyse oxidation, it rinses away with the water.

Trisodium Ethylenediamine Disuccinate (EDDS) is a next-generation chelator. The key difference from classic EDTA: EDDS is readily biodegradable. EDTA breaks down very slowly and reaches surface waters, where it can remobilise heavy metals from sediment. EDDS has comparable efficacy against Ca²⁺, Mg²⁺, Fe³⁺ and Cu²⁺, and then disappears in the environment.

What a chelator does in a formula

1. 1.Helps prevent calcium-salt deposits — hair feels lighter, cleaner, reflects light better.
2. 2.Supports cleansing in hard water — less surfactant is wasted binding ions, more is left to cleanse.
3. 3.Limits free-radical catalysis — helps protect keratin and pigment from oxidation, including from colour or bleach.
4. 4.Stabilises the formula itself — metal ions can speed oil rancidity and the breakdown of sensitive ingredients.

A chelator is not a “detox”

Marketed “detox shampoos” often work as a strong detergent that strips everything — lipids included. A chelator is selective: it binds metal ions and little else. It can be used at every wash, including on coloured hair. That is daily prevention, not a clarifying treatment.

A cosmetic does not soften water. It can bind calcium and magnesium ions and help protect hair from the effects of hard water.

Where it matters most

Anywhere water hardness is above about 200 mg CaCO₃/l — which covers most large cities in Poland, England, Denmark, Germany and Italy. Details in the next article.