This is mostly personal preference; I find the water phase comes out of its measuring cup more easily and completely, so I do it this way. If you prefer to do it the other way around, go for it. It usually does not matter. If the formulation uses Polawax, Emulsifying Wax NF, Olivem 1000, Ritamulse SCG (Emulsimulse, ECOMulse), BTMS-50, BTMS-25, Glyceryl Stearate SE, or Glyceryl Stearate (and) PEG-100 Stearate as the emulsifier, I’m quite confident that you can pour whichever phase as you desire and the formulation will succeed. I have probably made well over a thousand successful emulsions with these emulsifiers, pouring the water phase into the oil phase.
Some people believe that if you’re making an oil-in-water emulsion than you must pour the oil into the water and vice versa. This is not the case. The emulsifier the formulation uses determines the sort of emulsion you get—which phase is poured into which cannot change that. Some formulations/emulsifiers will specifically require that one phase is poured into the other. If that is the case for any of my formulations, I’ll make it abundantly clear in the instructions.
Posted in: Troubleshooting & Adjusting