I only use Distilled water. Last time I used tap water my soap never set up (and it was a 5 batch night with a tried and true recipe.) Ran out of distilled water and said, what the heck, everyone else uses tap. Soaps were semi-liqud in the morning (usually rock hard within 10 hours.) Since that episode I will never use tap again. I don't think its the castor. I use 20-25% in each batch, makes one mean silky bar! My conditioning score for my fave recipe is 56. My base recipe's conditioning score is 53. I cringe when I see recipes with conditioning scores of 50 and under, makes my skin itch just thinking about it. My recipes also contain 10% shea butter, and if it melted all the way when you melted your oils, then it can't be the shea, or the coconut oil, since soap during gelling gets much hotter than the melting points of both. Castor is a drawing oil that helps draw blood circulation, etc. But it does not draw moisture out of the skin in a soap IMO, it is a moisturizing oil, and perfect for increasing the conditioning properties in your soap.