Let’s talk about pH stabilisers.
The term ‘pH’ was introduced in 1909 by the Danish chemist Søren Sørensen.
In chemistry, pH is a quantity that measures the acidity or basicity of a solution.
pH values vary in a range from 0 to 14 where:
- a pH value of 7 indicates a neutral solution (example: distilled water at 25°C);
- a pH value less than 7 indicates an acid solution (example: coffee or healthy skin);
- a pH value greater than 7 indicates a basic solution (example: seawater).
The pH value can be determined electrically using an electronic instrument called a pH meter or chemically using litmus paper or chemical test kits.
Today, using a pH meter is considered the best way to measure pH, as it has many advantages, including speed and greater accuracy.
The skin has a slightly acidic pH (around 5) and it is essential to keep it in balance as it is the key to the skin’s protective barrier.
Clearly, the degree of acidity of the skin varies depending on the individual: the body region must be taken into account, plus other factors of endogenous (e.g. sweat and lactic acid) and exogenous (air pollution and diet) origin.
It is therefore essential to take the pH of the skin into account when defining the pH of cosmetic formulations. This is why so-called pH stabilisers are used in cosmetics. They serve to increase or decrease the pH that spontaneously occurs in a formulation when the various raw materials are mixed together.
Examples of molecules capable of modifying the pH of cosmetic formulations are:
- citric acid, when one wants to make the pH of a formulation more acidic;
- triethanolamine, when one wants to make the pH of a solution more basic.
By means of pH stabilisers it is possible to adjust, in fact stabilise, the pH so as to increase or decrease the pH of a formulation as required.