The unique properties of clays are essentially due to the small size of their particles, their structure and the negative charge they possess.
Benefits: Clays absorb water and increase in volume when they swell, forming a homogeneous liquid mixture. They can exchange ions with the environment where they are found and capture many molecules, both simple and complex. Also, they help adsorb sebum from the skin, refining the texture and helping to eliminate impurities.
Bentonite: Bentonite is a clay composed of 75% smectite, 15% illite and 10% kaolinite (Figure 1).
Figure 1: Characterization carried out by X-ray diffraction.
This combination of different types of mineral silicates improves the properties of their individual components:
-Smectite: Provides a good part of its properties, such as its great capacity for mass absorption and surface adsorption, due to its particular structure of stacked sheets that intercalate metal cations.
Calcium smectite is the most abundant in nature, it is capable of absorbing 36% of its volume of water and maintaining an excellent cation exchange capacity compared to many other clays (38 meq). An advantage of this natural smectite is that the calcium ions that are between the silicate sheets are united with weak chemical bonds, allowing a much better absorption of large molecules such as toxins and mycotoxins1.
-Illite and kaolinite: They have less absorption and adsorption capacity than smectite, but they provide other different properties. In particular, they have the ability to form a viscous, hydrated protective film with anti-inflammatory and regenerative properties for both plant and animal cells.
The use of clays in cosmetics is related to its ability to absorb sweat and fat, as well as its ability to adsorb toxins, water regulation and protective action of the skin. Also of interest is its refining and smoothing action on the skin by acting as a physical exfoliating agent and its high softness.
Table 1 lists the type of silicate with its action in cosmetic products.
Origin: Bentonite was formed by natural aging over thousands of years from volcanic ash. It comes from controlled deposits dating from the geological period called Oligocene, with an age of between 23 and 34 million years. It is produced through a process designed so that the clay does not suffer any type of degradation
Traditional uses: Clay has been used since ancient times due to its various characteristics: Remineralizing, healing, purifying, soothing. The great ladies of ancient Egypt knew the powers of clay and applied it to their faces to perform a facial cleansing before putting on makeup. Already at that time, a soft and light skin, without defects, was valued, and it was known that clay is an ally of choice in the beautification and maintenance of the skin. Clay was also included in the composition of different mixtures that the Egyptians used in cleaning and makeup preparations, combining ash and clay, as well as in the mummification process, for its disinfectant properties.
Bentonite is currently authorized as a food additive that belongs to the category of technological additives as a binder and anti-caking agent.
|Mineral Silicate||Property||Action in Cosmetics|
|Snectute||Adsorption||Balances the skin’s metabolism by eliminating toxing and impurities.|
|Illita||Absorption||Eliminates fat, sweat.|
|Kaolinite||High softness exfoliation||Care for sensitive skin.|