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Damaged Hair: The Hidden Perils Of Hard Water

Water - and more specifically the calcium within - can cause damage to your hair. The secret to defending your hair fibres ? Decalcification. Discover all there is to know to keep your locks strong, shiny and supple.

Water flowing from a shower head

Hard water, with its high calcium content, can cause hair breakage especially if it's already damaged, bleached, or processed. Often underestimated for its potential harm, hard water can be a silent assailant to your strands, weakening and dulling them.

The key to saving your hair fibres from this hard water is hair decalcification. In this article, we’ll dive into the science behind why hard water is detrimental to your hair and the practical tips you need − including how to decalcify – in order to protect your hair from the dangers of hard water.

Why Water Damages Your Hair?

Water is life, and it plays a crucial role in maintaining our overall well-being. However, when it comes to your hair, the type of water you expose it to can either be a blessing or a curse. Hard water is water that is rich in minerals, predominantly calcium and magnesium.

When we think of hard water, we often think about limescale - that chalky deposit that builds-up around taps and in the depths of your kettle - but when it comes to hair, it’s the calcium that is the real issue. Strange, right? Because when we think of calcium, we often link it to strong, healthy bones and teeth but when it comes to hair, calcium buildup is not your friend - it can, in fact, lead to a range of problems, including hair weakening and breakage. These hair concerns can be signs of hard water on hair causing damage.

What Type of Damage Can Calcium Cause to Your Hair?

Now that we know why calcium is good for our bodies but bad for our hair when exposed regularly,
here are 3 types of damage that calcium can cause to your hair:


Calcium reacts with the proteins in your hair fibres causing them to stiffen. This stiffness can make your hair feel coarse and difficult to manage, leading to more breakage during styling or brushing.


Wondering what does hard water buildup look like on hair? When your hair is exposed frequently to hard water, calcium can form a coating on your hair, making it look dull and lacking luster. This layer can prevent moisture on the hair shaft, leaving it dry and lifeless.


Calcium can weaken the protein structure of your hair, making it more prone to breakage. This is especially concerning for those with already damaged or porous hair, as it exacerbates the problem.

What Type of Damage Can Calcium Cause to Your Hair?

Now that we know why calcium is good for our bodies but bad for our hair when exposed regularly,
here are 3 types of damage that calcium can cause to your hair:

How to Decalcify your Hair and Protect it from Hard Water?

Hair decalcification is the process of removing the damaging calcium buildup from your hair. This procedure is essential for maintaining healthy, lustrous hair, particularly if you live in an area with hard water.

There are several methods for hair decalcification, including specialized shampoos, conditioners, and treatments designed to dissolve and remove excess calcium. Regular use of these products can help restore the natural balance of your hair and prevent further damage. Here are 4 hard water hair treatment ideas:

These Products Could be for You!

To keep your hair looking its best, implement hair decalcification into your routine and use products designed to combat the hard water effects on hair. With the right hair care routine and a little extra attention, you can keep your hair strong and healthy, even in areas with notoriously hard water.

What Products to Use to Avoid Hard Water Damage?

Did you know, damaged hair absorbs 3x more calcium than healthy hair?

That’s where the new hair strengthening range, Première, comes in, as it has been specifically formulated to decalcify your hair fibres using citric acid and glycine – giving your hair a mineral detox.

The Kérastase Première Concentré Décalcifiant Ultra Réparateur boasts the highest percentages of each ingredient: 3% citric acid to eliminate the calcium buildup, neutralizing dullness and stiffness. Added to that is 5% glycine, an amino acid, that penetrates the hair to reconnect broken keratin links (caused by the calcium) to reduce breakage. The dual action repair, both outer and inner repair, can recreate 99%* of your hair’s original strength.

Sounds too good to be true - we know - but it’s not magic, it’s science. Find out how the Kérastase Première Concentré traps and eliminates the excess calcium with this experiment done by Edine Ahbich, Kérastase Scientific Director.

At-Home Decalcification Ritual

The key to the Première range is the power of layering (a hot new hair trend, you can read more about hair layering here) to remove the calcium deposits from the outside and inside of your hair fibre. By layering our powerful Première clarifying pre-shampoo concentré with the shampoo, the active ingredients are able to penetrate the different layers of your hair for optimal decalcification and mineral detox.

Kérastase Première Pre-Shampoo Treatment for decalcifying layering ritual


Start with the Kérastase Première Concentré Décalcifiant Ultra Réparateur, a pre-shampoo concentrate that is the clarifying hero of the collection. Use on slightly wet/damp hair and should not be rinsed before applying the shampoo (layer 2).

With 3% citric acid and 5% glycine, it decalcifies your hair reducing stiffness, boosting shine, recreating 99%* of hair’s original strength and reducing breakage by 93%*.

Kérastase Première Shampoo for decalcifying layering ritual


Our Kérastase Première Bain Décalcifiant Réparateur should be applied directly on top of the Concentré (you can add a little water to emulsify, if needed).

Its creamy texture and voluptuous foam gently cleanses away calcium overload and neutralizes dullness and breakage. Hair is left healthier, shinier and renewed.

Kérastase Première Conditioner for damaged hair


Once hair is towel dried you can layer on the Kérastase Première Fondant Fluidité Réparateur, or the Masque Filler Réparateur.

The lightweight formula of the conditioner quickly gets to work to restore moisture and fluidity. In fact, hair is left 7x smoother, * 82% shinier* and with 86% more moisture. *

The rich, creamy mask should be left on towel-dried hair for 5 minutes in order to penetrate fibres to repair and rebuild inner strength.

Kérastase Première Huile Gloss to repair damaged hair


Calcium doesn’t just cause breakage, it enhances damage and dryness leading to frizz, so our Kérastase Première Sérum Filler Fondamental is designed to repel humidity and protect against heat up to 230 ºC.

Huile Gloss Réparatrice is a nourishing oil that seals spit ends and boosts shine. It’s the perfect addition to polish hair after heat styling or to tame flyaways if you tend to leave you hair to air dry.

In-Salon Decalcification Ritual

Kérastase Première salon-exclusive routine to repair damaged hair Kérastase Première salon-exclusive routine to repair damaged hair

For the ultimate hair decalcification in salon, your hairdresser can offer our salon-exclusive clarifying Concentré Liquide Resurfaçant.

After your hairdresser layers the Concentré with the Bain, they will rinse. Then they will apply the Kérastase Concentré Liquide Resurfaçant with the Masque, before rinsing again.

This double layering technique offers the highest exposure to citric acid and glycine in one hit to intensely decalcify - removing calcium - to reverse persistent stiffness and to seal in shine and suppleness. Expect hair that is stronger, healthier and shinier.

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