Hello: I have been using more natural preservatives in my skin cream but would like to try organic 190 proof grape alcohol as a preservative. I have two questions. My understanding is that the alcohol needs to be 15-20% to effectively preserve the skin cream. But is that of total volume or just the water phase. Second at what stage do you add the alcohol and should it be warmed to the temp of the emulsion? I assume cool down phase but I find that my emulsion breaks. Any tips appreciated.