The requirements of an effective sunscreen include high solubility of
organic filters in the vehicles, efficient dispersion of physical
filters, absence of crystallisation after application onto the skin
surface and lack of aggregation phenomena of micronised powders into
product. Moreover, an effective sunscreen requires appropriate inorganic
filters load as well as optimum wetting of mineral filters and the
formation of a transparent limit layer over the skin surface.
Photo-stability is another essential requisite for high SPF products.
Nowadays, new synthesis and advanced purification process provide the
formulator with pure, chemically defined hydrocarbon molecules having
interesting potential for use in sunscreen products, high photostability
and the capability to stay onto the skin surface without diffusing. New
methods of micronisation and coating of physical filters provide a wide
range of particles dimensions, different degrees of lipophilic or
hydrophilic behaviour and enhanced transparency. When associated with
branched chain hydrocarbons they yield an improvement in effect/dose
ratio and form a very transparent film over the skin surface. Practical
examples of formulation demonstrate the wide range of combinations made
possible by such high-technology ingredients.