I've done a few trial batches of liquid soap but they need some work before I figure it out. I want to make it with cp method to avoid scorching the milk. I add my lye to the milk (rather than later in the trace stage)I will be using distilled water for dilution. My questions are: 1) does liquid soap this way need a preservative? 2)whats the typical shelf life of liquid soap? 3)do i need a ph tester or is zap testing the paste enough? Any extra tips are welcome Thanks!