Can I Thin Out a W/O Emulsion by Adding an O/W Emulsifier?
I’m developing a ZnO (20%) moisturizing sunscreen, with ~33% oils and ~19% water (final formula concentrations pending). My emulsifiers are Glyceryl Stearate (3%) and Sorbitan Stearate (1%), with some thickeners/stabilizers at low concentrations (e.g. Xanthan, 0.1%).
The emulsion is stable and spreads easily enough, however the product is supposed to be dispensable through a pump. As it currently stands, the lotion is more like a butter that is too viscous to be poured.
I’ve seen that some similar (W/O) products on the market have low concentrations of emulsifiers typically used for O/W emulsions. Is this out of ignorance, or does it help decrease viscosity without destabilizing the emulsion? I have been thinking of experimenting with Glyceryl Stearate Citrate, but I do not know if it would be a waste of funds (nor how much to start out using).
One other thing to consider: We are sticking with natural/biodegradable ingredients, so some of the traditional solutions aren’t available to us.
If not the emulsion, do you have any other suggestions to decrease viscosity?