Consider what are the key performance and sensory characteristics you want in the final product, and what other ingredients you intend to use. Key questions to consider include:-
- What type of emulsion do you want to make? Oil-based dispersions give the best results in W/O emulsions. O/W systems are effective with either oil-based or water-based dispersions, but water-based dispersions give greater flexibility. Another useful approach in some cases is to use both oil-based and water-based dispersions in the same formulation.
- Is transparency important? If so, select one of the Solaveil™ Clarus range to minimize whitening on skin. If transparency is not important, for example in a baby sun product, a Tioveil™ or Tioveil 50 dispersion may give better cost-effectiveness.
- Is water-resistance required? Oil-based dispersions tend to give better water-resistance. However Solaveil CT-10W, which is a water-based dispersion but uses hydrophobic Titanium dioxide, also gives good water-resistance.
- What skin feel is required? Water-based dispersions tend to give a drier skin feel than oil-based. If using an oil dispersion, select a carrier which helps to deliver the skin feel characteristics you want in the final formulation.
- Are there any organic UV filters in the formulation? A dispersion based on C12-15 Alkyl Benzoate can be helpful in this case, as this ester is an excellent solvent for organic filters. However certain organic filters can give a yellow colour in combination with titanium dioxide; this can be reduced or even eliminated by using a water-based titanium dioxide dispersion.
For specific guidance on your application, please contact your local Croda applications laboratory for a recommendation.
In principle any of the dispersions can be used in decorative cosmetics; the choice depends on other characteristics of the product, in particular skin feel as outlined above. Water-based dispersions tend to give a drier skin feel than oil-based. If using an oil dispersion, select a carrier which helps to deliver the skin feel characteristics you want in the final formulation. Many modern cosmetic products are being formulated as silicone-in-water or water-in-silicone systems; for these, the silicone-based dispersion Tioveil CM is ideal.
For transparency on skin, one of the Solaveil Clarus dispersions should be used. As to which specific dispersion to use, this depends on the particular skin feel characteristics required. Generally, either Solaveil CT-200 or the water based dispersions (Solaveil CT-10W, Solaveil CT-12W) give the most preferred skin feel. However remember that the other ingredients in the formulation also exert a great influence on sensory properties.
Some organic UV filters and other actives such as certain vitamins, can give a colour in formulations with titanium dioxide. For example butyl methoxydibenzoylmethane (avobenzone) tends to give a yellow colour. This can be avoided by using a titanium dioxide dispersion which goes into the opposite phase to the organic active; for example BMDM is oil-soluble, so using a water-based titanium dioxide dispersion (for example Tioveil AQ or Solaveil CT-10W) can substantially reduce or even eliminate this yellow colour. Croda is also working to develop new coatings for titanium dioxide which will prevent even oil-dispersed titanium dioxide from interacting with these organic actives.
There are very few ingredients which are incompatible with the dispersions. There are a few specific incompatibilities, depending on which type of dispersion is used. Please contact your Croda sales representative or your local Croda applications laboratory for specific guidance on the dispersion you are using.
We use the in-vitro technique of Diffey and Robson (J.Soc.Cosmet.Chem, 40, 127-133 (May/June 1989)), using either an Optometrics SPF-290 analyser or a Labsphere UV-1000S UV transmittance analyzer. Standard products of known in-vivo SPF are used to ensure consistency of results.
Croda commissions external, recognized test laboratories to conduct in-vivo SPF tests according to published standard methods (eg. the International method in Europe, or the FDA protocol in the USA).
Many different aspects of the formulation can influence the SPF. For further information, consult the following reference:-
J.P.Hewitt, “SPF Modulation: Optimising the Efficacy of Sunscreens”, in “Sunscreens: Regulations and Commercial Development”, 3rd edn., edited by N.A.Shaath; published by Taylor & Francis, Boca Raton, 2005; pages 385-412.