Every aqueous solution has a potentia Hydrogenii, or pH, value. pH is a unit of measurement for the amount of H atoms and therefore how acidic or alkaline a substance is and can only be used to measure something that is water-based. As such, you can’t measure the pH of oils. The pH scale goes from 0 to 14 with the neutral point at 7. Acids always have more Hydrogen H+ ions while alkalines have more Hydroxide OH ions.


Everything between pH 0 and pH 7 is an acid pH value. More H Ions than OH ions = more acidic. Example: lemon juice or treatments.

This allows a hair product to re-establish a proper pH after it has been being treated with an alkaline product like a permanent hair color, lightener, perm, straightener, or relaxer.


Everything between pH 7 and pH 14 is an alkaline pH value. Less H Ions than OH ions = more alkaline. Example: oven cleaner or bleach/de-colorizer.

This allows a hair product to change or modify the hair’s structure both inside and out. Alkalinity swells the cuticle layer, allowing the product to penetrate into the cortex. However, products that are too high in alkalinity can cause the cuticle layers of hair to break off.


The neutral point is pH 7. Pure water contains H and OH Ions in equal measure. The pH range for hair and skin is between 4.5 and 5.5. Products that are neutral to hair and skin have to match this acidic pH value.


pH tells only about the concentration of “free” [H] / [OH] ions in a aqueous solution. pH says nothing about how many “reserve ions” [H] / [OH] are available. And diluting with water will not change the pH significantly.

ph value scale


The pH scale is a convenient way of expressing hydrogen ion concentration by simply referring to its logarithmic power.

The pH value does not tell how gentle or aggressive a product is and it won’t tell the power of a product. The chemical makeup of a product consists of more important components, with the pH value being only one. How gentle or damaging a product is can’t be determined by a low or high pH value.

By adding water to an acid or alkaline base, H and OH is diluted in the same degree keeping the pH value essentially the same. Diluting chemical products e.g. hair color with water does not change the pH value but does lower the concentration of the dyestuffs.

For product performance it is not important if chemists use pure or diluted concentrations or how they mix it. Only the effect on hair is important. Goldwell products are designed to deliver the best performance along with exceptional care.


Most permanent hair coloring products require an alkaline solution in order to drive pigments into the hair shaft.

Alkaline solutions swell the cuticle and allow the color molecules to be deposited into the inner cortex of the hair. Therefore alkalines like Ammonia are in most color products.

Hydrogen peroxide lotion (H2O2) is always acidic for stability and to avoid unwanted oxidization. It registers below pH 4 and is used as an oxidizing agent in permanent dyes. The alkalinity of the hair color de-stabilizes the hydrogen peroxide lotion, releasing oxygen and activating the oxidative reaction needed for coloring.

Lightening powder (bleach) is around 8.5 to 10.5 pH. When mixed with peroxide, the solution is still alkaline enough to lift natural and artificial color from hair.

Since alkalinity is necessary for some coloring products, it’s also important to acidify the hair and bring the pH back to a 4.5 to 5.5 level. In order to reduce the swelling in the cortex and make the cuticle compact and smooth, an acid pH shampoo and/or treatment should be used after an alkaline service.


Learn more about Chemical Backgrounds here.

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