[oksana.walker]

You add salt (NaCl) to the water phase to increase repulsion and if you worry about preservatives being distributed between two phases, add glycol.

[oksana.walker]

You can have a water phase with 1-2% of salt, your water soluble actives, humectants and preservatives and your second phase with oils, antioxidants and oil soluble actives. That’s it. You can even have tri-phase product if you add some silicone. It is very simple and easy