By Elena L. Peters - Beauty & Hair Editor
24 october 25

Chelating shampoo and chelating treatment: removing hard-water metals from hair

ChelatingHard waterOLAPLEX

Every wash, swim or splash in hard water leaves microscopic minerals and metal ions on and inside the hair fibre. Over time these deposits build a dull film, block moisture and interfere with colouring, lightening and smoothing or keratin treatments. A chelating shampoo and a chelating treatment solve the root cause: they bind calcium, magnesium, copper and iron so the metals rinse away cleanly.

This guide explains chelation in plain language, answers the hard-water questions clients ask, and shows the OLAPLEX products we stock for it: the OLAPLEX Broad Spectrum Chelating Treatment and No. 4C.

Short answer: Chelating agents grip metal ions and make them water-soluble, so hard-water minerals and pool or pipe metals rinse out of the hair instead of dulling it and fading colour. Our advice: chelate in the salon before a chemical service, and keep up a clarifying wash at home between visits, followed by conditioner or a mask.

What is a chelating shampoo, and what is a chelating treatment?

The word chelation comes from the Greek chele, claw. In cosmetic chemistry a chelating agent grips a metal ion at several binding points and forms a stable, water-soluble complex that rinses off the hair. Chelators such as EDTA, MGDA, EDDS and citric acid target the common ions, calcium, magnesium, copper and iron, and neutralise their reactivity so they can be removed during rinsing.

Infographic: pollution and metal build-up on the hair surface
What hard water and pollution leave on the hair surface, wash after wash.

A chelating shampoo carries these agents in a cleansing base, for regular maintenance. A chelating treatment is a concentrated professional step with a longer processing time, for deep removal before a chemical service. Both do three things:

  • Remove the invisible mineral film that blocks conditioners and masks.
  • Reduce metal-catalysed oxidation during colour or bleach, for truer results.
  • Bring back softness and shine in hard-water conditions.
Diagram of EDTA chelating a copper ion
The claw: one EDTA molecule binding a copper ion at several points.

How chelation works: the science in five steps

Chelating agents contain multiple donor sites (ligands) that coordinate to a single metal ion. The sequence is recognition, binding, complex formation and removal by rinsing.

Infographic: chelation in five steps
Recognition, binding, complex formation, rinsing: chelation in five steps.

Copper and iron matter most: they catalyse free-radical reactions that fade colour and damage proteins. By binding these ions, chelating agents reduce oxidative stress and make salon services more predictable.

Chelating vs clarifying shampoo: what is the difference?

Clarifying removes surface oils and product residue with surfactants. Chelating targets the mineral and metal ions embedded within the fibre with chemical binding. Clarifying is for product build-up; chelating is the step for hard water, pre-colour preparation and green or brassy casts.

Clarifying vs chelating
Clarifying shampoo
Surfactants lift oils, silicones and styling residue from the surface. Use for product build-up.
Chelating shampoo or treatment
Chelating agents bind calcium, magnesium, copper and iron inside the fibre and rinse them out. Use for hard water, before colour, and for green or brassy casts.
Comparison chart: clarifying versus chelating in hair care
Two different jobs: surface residue versus embedded metals.

What does hard water do to your hair?

Calcium and magnesium from hard water form stubborn films that make hair feel rough and block conditioning. Copper from pools or pipes and iron from plumbing accelerate oxidation, which leads to colour fade, green or brassy casts and more breakage. Removing these ions leaves a cleaner hair surface and lets care products penetrate evenly.

Hair cuticle with mineral build-up versus after chelation, 3D microscopy view
The cuticle under mineral build-up, and the same surface after chelation.

Does hard water make hair greasy or heavy?

What feels greasy is often not sebum but the mineral film: hair feels coated, conditioner does not absorb, products stop working, and fine hair loses volume under weighty deposits. More shampoo does not remove a mineral film; a chelating shampoo does, and afterwards conditioners and masks penetrate again.

Is hard water bad for coloured and blonde hair?

Copper and iron catalyse the free-radical reactions that fade colour and damage proteins during oxidative services. On blonde or lightened hair the copper shows as a green cast and iron as brassiness; on colour-treated hair as uneven tone and fast fade. This is why chelating before colour gives truer, more predictable results.

Swimmers: chlorine, copper and green hair

Pool water combines chlorine with copper, and the copper deposits on lightened hair as the well-known green cast. For clients who swim often, a chelating shampoo is the swimmers' shampoo; our advice is to chelate before any colour or lightening service.

Signs your client's hair needs chelating

  • Dullness Loss of shine, or a coated feel.
  • Colour problems Green or brassy tones, uneven colour, or fast fade.
  • Products stop working Conditioner does not absorb.

OLAPLEX Broad Spectrum Chelating Treatment

We stock the OLAPLEX Broad Spectrum Chelating Treatment. For application, processing time and how often to use it, follow the directions on the pack. More on the OLAPLEX range in our OLAPLEX bond-building guide.

OLAPLEX Broad Spectrum Chelating Treatment bottle
OLAPLEX Broad Spectrum Chelating Treatment.
Pro tip: we chelate before a chemical service, not after it, so colour, lightening or smoothing goes onto a clean fibre.

OLAPLEX No. 4C: Bond Maintenance Clarifying Shampoo

For the home routine between salon visits we recommend OLAPLEX No. 4C Bond Maintenance Clarifying Shampoo (250 mL). Its label reads “DEEP CLEANS, SOFTENS, RESTORES SHINE & CLARITY” and “ALL HAIR TYPES”. It is also available as a 1000 ml bottle.

OLAPLEX No. 4C Bond Maintenance Clarifying Shampoo bottle
OLAPLEX No. 4C Bond Maintenance Clarifying Shampoo.

At-home maintenance between salon visits

  • A clarifying wash between visits Our advice: more often with very hard water or frequent swimming, never daily.
  • Always condition afterwards to reseal the cuticle.

For your client's home routine we stock OLAPLEX No. 4C, and for the conditioning step after it OLAPLEX No. 5 Bond Maintenance Conditioner or OLAPLEX No. 8 Bond Intense Moisture Mask.

OLAPLEX No. 4C Clarifying Shampoo and No. 8 Bond Intense Moisture Mask
OLAPLEX No. 4C and No. 8.

Chelating for blonde, coloured, curly and fine hair

Blonde or lightened hair
Helps keep green or brassy casts away.
Colour-treated hair
Supports truer tone and longer-lasting results.
Curly and textured hair
Improves softness and product absorption.
Fine hair
Removes weighty deposits for better volume and movement.

How often should you chelate?

Our advice: in the salon, chelate before every chemical service. Before a smoothing or keratin service the same rule applies; our taninoplastia guide and the formaldehyde-free keratin guide both start from a clean, mineral-free fibre. For colour or lightening after chelating, the pack of OLAPLEX No. 1 Bond Multiplier names its place itself: “MIX WITH LIGHTENER, COLOUR, OR CHEMICAL SERVICES”. At home: a clarifying wash between visits, more often for very hard water or frequent swimming, never daily.

Why chelation belongs on the salon menu
Predictable colour
Copper and iron out of the fibre means less oxidation, truer tone and less fade.
Better adhesion
Smoothing and keratin systems bond to a clean canvas.

Frequently asked questions

What is a chelating shampoo?
A shampoo whose formula contains chelating agents (such as EDTA, MGDA, EDDS or citric acid) that bind calcium, magnesium, copper and iron so they rinse out of the hair.
Chelating vs clarifying shampoo: what is the difference?
A clarifying shampoo lifts oils, silicones and styling residue from the surface with surfactants. A chelating shampoo binds calcium, magnesium, copper and iron in the fibre and rinses them out.
What is the difference between a chelating treatment and a chelating shampoo?
A chelating treatment is a concentrated professional step with a longer processing time, for deep removal before a chemical service. A chelating shampoo carries the same kind of agents in a cleansing base, for regular maintenance.
How do you get hard-water minerals out of your hair?
More shampoo does not remove a mineral film; a chelating step does. Our advice: in the salon, chelate before every colour, lightening or smoothing service; at home, a clarifying wash between visits, always followed by a conditioner or a mask.
Does chelating dry out the hair?
Hair can feel drier straight after a chelating step, which is why we always follow with a conditioner or a mask.
Can I use a chelating shampoo every day?
We advise against daily use. Adjust the frequency to your water and exposure: more often with very hard water or frequent swimming.
Is chelating a good idea for coloured hair?
Yes, in our view. Removing copper and iron reduces the metal-driven oxidation that fades colour, and gives a cleaner base for toners. On blonde or lightened hair we follow with a conditioner or a mask straight away.
How long before colour should I chelate?
Before the chemical service, not after it. For processing time and the gap between chelating and colouring, follow the directions on the product you use.

Chelation is hair science, not just a deep clean: take the metals and minerals that drive dullness and chemical unpredictability out of the fibre, and colour and smoothing services become more predictable. The full range is on the OLAPLEX brand page; professional products under OLAPLEX Professional.

References

Peer-reviewed literature

  • Srinivasan, G., & Srinivasan, S. (2014). Effects of hard water on hair. International Journal of Trichology, 6(3), 137-139. doi:10.4103/0974-7753.139078
  • Luqman, M. W., Ramzan, M. H., Javaid, U., Ali, R., Shoaib, M., & Luqman, M. A. (2018). To evaluate and compare changes in baseline strength of hairs after treating them with deionized water and hard water and its role in hair breakage. International Journal of Trichology, 10(3), 113-117. doi:10.4103/ijt.ijt_115_16
  • Srinivasan, G., & Chakravarthy Rangachari, S. (2016). Scanning electron microscopy of hair treated in hard water. International Journal of Dermatology, 55(6), e344-e346. doi:10.1111/ijd.13141
  • Yang, F., Zhang, Y., & Rheaume, M. (2015). The role of chelating agents and amino acids in preventing free radical formation in bleaching systems. Free Radical Research, 49(11-12), 1408-1418. doi:10.3109/10715762.2015.1087643
  • Marsh, J. M., Davis, M. G., Blalock, J. S., Scott, A. E., Harding, C. R., & Ismaeli, H. A. (2015). Preserving fiber health: reducing oxidative stress throughout the life of the hair fiber. International Journal of Cosmetic Science, 37(Suppl 2), 16-24. doi:10.1111/ics.12285
  • Naqvi, K. R., Marsh, J. M., Godfrey, S., Davis, M. G., Flagler, M. J., Hao, J., & Chechik, V. (2013). The role of chelants in controlling Cu(II)-induced radical chemistry in oxidative hair coloring products. International Journal of Cosmetic Science, 35(1), 41-49. doi:10.1111/j.1468-2494.2012.00755.x
  • Zhang, X., Niu, L., Gao, Z., Zhao, L., Liu, Q., Pan, L., & Liu, G. (2016). Trace metal ions in hair from frequent hair dyers in China and the associated effects on photo-oxidative damage. Journal of Photochemistry and Photobiology B: Biology, 156, 1-7. doi:10.1016/j.jphotobiol.2015.12.027
  • Marsh, J. M., Gray, J., & Tosti, A. (2009). Copper and calcium uptake in colored hair. Journal of Cosmetic Science, 60(4), 479-480. doi:10.1111/j.1468-2494.2009.00522.x
  • Oviedo, C., & Rodriguez, J. (2003). EDTA: The chelating agent under environmental scrutiny. Quimica Nova, 26(6), 901-905. doi:10.1590/S0100-40422003000600020
  • Sebetic, K., Sjerobabski Masnec, I., Cavka, V., Biljan, D., & Krolo, I. (2008). UV damage of the hair. Collegium Antropologicum, 32(Suppl 2), 163-165. PMID 19138021
  • Trueb, R. M. (2015). Oxidative stress in ageing of hair. International Journal of Trichology, 7(3), 94-100. doi:10.4103/0974-7753.167266
  • Gavazzoni Dias, M. F. (2015). Hair cosmetics: An overview. International Journal of Trichology, 7(1), 2-15. doi:10.4103/0974-7753.153450
  • Catala, A., Gonzalez, V., Romani, J., & Agusti-Mejias, A. (2022). Pseudo green hair. Indian Journal of Dermatology, 67(2), 215-217. doi:10.4103/ijd.ijd_880_21
  • Luqman, M. W., Ali, R., Khan, Z., Ramzan, M. H., Hanan, F., & Javaid, U. (2017). Effect of topical application of hard water in weakening of hair in men. International Journal of Trichology, 9(1), 165-166. doi:10.4103/ijt.ijt_4_17

Cosmetic chemistry and formulation

Cosmetics & Toiletries (2014), Deciphering chelating agent formulas, 129(11); Personal Care Products Council (2024), wINCI, definition of chelating and sequestering agents; SpecialChem (2024), Disodium EDTA (chelating agent), cosmetic ingredient database; National Center for Biotechnology Information (2024), PubChem compound summary CID 6049, ethylenediaminetetraacetic acid.

Water quality and hard-water research

U.S. Geological Survey (2023), Water hardness and alkalinity, National Water Quality Assessment Project; World Health Organization (2011), Hardness in drinking-water, background document for the WHO Guidelines for Drinking-water Quality, WHO/HSE/WSH/10.01/10/Rev/1; TRI Princeton (2023), Aqua-mane-ia: the science and art of water on your hair.