When you make a batch of soap, you have to be extremely accurate when measuring right? I'm confused about masterbatching being accurate in your mini batches from your main masterbatch. How do you know if your really getting let's say 5% castor oil when pouring your mini batch from your masterbatch? Every oil has a sap value so how do you really know how much lye to use. I know you should mix it up and everything but I can't wrap my head around the fact of accuracy. Please tell me what I'm missing!