Nerd info about pH (for those who want to know more).


pH is a way of measuring the acidity of a liquid. The scale indicates whether the liquid is acidic, neutral or alkaline by measuring the amount of hydrogen ions (H+) and hydroxide ions (OH-) in the liquid. It is important to note that pH can only be measured when a substance can dissolve in water.

Ions are charged particles that form when an atom loses or gains an electron. Atoms consist of protons, neutrons and electrons, where protons are positively charged, neutrons are neutral and electrons are negatively charged. When an atom loses or gains an electron, the number of positive protons and negative electrons in the atom changes, and an ion is formed. Ions play an important role in chemical reactions and are essential for many biological processes.

Neutron (neutral) Proton (+) Electron (-)

Hydrogen ions are positively charged, meaning they lack electrons and therefore have a positive charge. Hydrogen ions can form when a hydrogen atom loses its single electron and only one proton remains. On the other hand, hydroxide ions have a negative charge, which means they have excess electrons and therefore have a negative charge. Hydroxide ions can be formed when a water molecule is split, releasing a hydroxide ion (OH-) and a hydrogen ion (H+).

These two ions, hydrogen ions and hydroxide ions, play an important role in chemical reactions and are fundamental to understanding the pH scale and acid-base chemistry.

PH scale

The pH scale is a logarithmic scale that ranges from 0 to 14, with 7 being neutral. Values ​​lower than 7 indicate acidity, while values ​​higher than 7 indicate base/alkalinity. Each step on the scale corresponds to a tenfold increase or decrease. Therefore, a pH of 5 will be 100 times more acidic than a pH of 7, while a pH of 0 will be 10 million times more acidic than a neutral pH of 7, and a pH of 14 will be 10 million times more basic/alkaline.

The Richter scale for measuring earthquakes is also logarithmic and based on the base number 10. Each step on the Richter scale corresponds to a tenfold increase in the strength of the earthquake. For example, an earthquake measuring 6 on the Richter scale will be ten times stronger than an earthquake measuring 5, while an earthquake measuring 7 will be a hundred times stronger than an earthquake measuring 5, and an earthquake measuring 8 will be a thousand times stronger than an earthquake measuring 5, and so on.


The pH of hair, skin and scalp is 4.5 to 5.5. This is not the pH of the hair, skin and scalp itself, but of the protective layer that lies on the surface. This layer, which is a combination of water and oil, is called the acidity barrier/sebum. The acidity barrier is produced by the skin's sebaceous and sweat glands.


The acidity barrier on the hair is destroyed or disturbed when we use products with a high pH value, such as permanent fluid, color or bleaching powder. This causes the hair to swell and forces the hard cuticles to stretch/open. However, this condition is necessary for chemical treatments to work properly. The important thing is to restore the acid balance as soon as the chemical treatment is finished.


To understand the effect pH has on hair fibers, it is necessary to understand hair chemistry. Hair fibers are made up of keratin proteins. Keratin is formed when amino acids combine, which is affected by pH. These amino acids belong to two groups: those with an acidic carboxyl group (-COOH) and those with a basic/alkaline group (-NH2).

Anything that produces positive ions (H+) when dissolved in water is called an acid. When the hair is wet, the acidic part of the amino acid releases positive hydrogen ions.

The hair fiber cannot dissolve in water, but some of the amino acids release positive hydrogen ions.

Anything that produces negative hydroxide ions (OH-) when dissolved in water is called basic/alkaline. When the hair is wet, the basic part of the amino acid releases negative hydroxide ions.

Normal hair does not have an equal number of acidic carboxyl groups (-COOH) and alkaline groups (-NH2). This means that wet, normal hair does not have an equal number of positive and negative ions. Wet, normal hair is not neutral, but is slightly negatively charged because the hair has released positive hydrogen ions.

To return to a neutral balance, wet, neutral hair needs the positive hydrogen ions it can get from a slightly acidic solution.


Protein chains can be both positively and negatively charged. This is because the proteins in the hair have both an alkaline part and an acidic carboxyl group part.

Opposite electrical charges attract each other, while like electrical charges repel each other. You might remember when we played with magnets as kids?

SALT BRIDGES. This attraction between opposite charges in the acidic and alkaline part of the protein chains stabilizes the hair fibers. These attractions are called salt bridges.

The attraction between positive and negative charges makes the hair strong and controls that the hair does not swell/open the cuticle.


If we add strong acidic or alkaline liquids to the hair, the hair will start to swell/open.

Strong alkaline products produce many negative ions. The keratin protein in the hair will lose its positive charges and only the negative charges will remain. This results in all the negative charges in the protein starting to repel each other, causing the hair to swell/open. The same thing will happen if the hair is exposed to strong acidic liquids, but then the remaining charges in the hair will be positively charged.

Swelling/opening of the cuticle is a process that weakens the hair. This is because the hair is no longer compact and the protein bonds are no longer strongly bound to each other.

DISULFIDE BRIDGES. Chemical treatments break down some of the disulphide bridges in the hair and thereby increase the number of negative charges in the hair protein (e.g. cysteic acid - often called cysteate - at close to neutral pH it takes the form -O3SCH2CH(NH3+)CO2−. It is an amino acid that is generated in the oxidation of cysteine, where a thiol group is completely oxidized to a sulfonic acid/sulfonate group). This causes the hair to have a different electrical charge than it originally had.

The result is that chemically treated hair needs a more acidic liquid to balance the internal negative charges in the hair's protein. In general, we can say that a liquid applied to the hair after a "harmful" chemical treatment should have a pH between 3 and 5 to restore the correct electrical balance in the hair. The more chemically damaged the hair, the closer to pH 3 the liquid we apply after the chemical treatment should be.

However, low pH after a chemical treatment will not always be enough to restore the hair's original structure. This is especially true when chemical treatments have been too strong or have affected the hair for too long, which may have destroyed or disrupted disulfide bonds or, in the worst case, peptide bonds. The quality of the hair before we start a chemical treatment and the desired result should always be considered before we start the treatment. If we see or think that the hair is too bad for the desired treatment, these assumptions are usually correct J

The quality of the hair is always decisive before we choose a permanent liquid or a relaxer product. It should also be taken into account when we determine the degree of lightening when dyeing. For example, bleaching versus dyeing, 3% H2O2 versus 12% H2O2. The solution to get good quality hair after a chemical treatment is to choose the right chemical products/treatment, follow recommended times (1), do not take too big "steps" - go from dark blonde to platinum blonde or sometimes refrain from such a treatment. Hair treatments with different ingredients containing amino acids can alleviate any damage after a chemical treatment, but the best choice is if the client has a healthy diet that provides optimal hair with respect to DNA. In addition, shampoos and hair treatments that build up keratin are used before chemical treatments to make the hair as good as possible. It is better to train for a marathon before the race than after the race J

(1) Remember that hydrogen peroxide (H2O2) is sometimes your hair's friend, but can also be your hair's enemy. In case of permanent fixation, H2O2 acts as a regenerator of the SS bonds, but should preferably not act for longer than 10 minutes. After this, the product will start to oxidize in other areas that are easily negatively affected and the end result of the treatment will not be as desired. This is especially true if the hair has been chemically treated from the start (frizzy, dull).

Lime: In some areas there is a lot of lime (CaCO3) in the water. This lime can settle on the hair and interfere with any chemical treatment. Lime dissolves very poorly in water, but can be easily removed with acidic solutions such as citric acid. We recommend having powdered citric acid in the salon that can be mixed with water and applied to hair after shampooing, leave on for 2-3 minutes and rinse. This treatment has no negative effects - carbon dioxide is formed, which is then spontaneously converted into water and CO2. The customer gets clean hair and you get a clean "raw material". (You can also use this in the shower at home to remove limescale, or acetic acid mixed with washing up liquid also works very well.


We should always use shampoos that have a pH value between 4.5 and 5.5 in order for the hair and scalp to keep the acidity barrier intact. This will protect the hair and skin from drying out and keep the hair in a compact structure.


pH measurement measures the exact pH value of a water-soluble product. Some products do not have a pH indicated, this can then be measured with pH paper/indicator. You can also measure the pH value of the water in your salon, this can be very important because the pH value of the water can affect the products you use in the salon. For example, if the water is alkaline, it will neutralize any acidic products you use. With the pH indicator, you can also measure the pH value of the hair after a perm. If the device shows an alkaline pH, you should do another acidic rinse.

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