Hi Carla! I ran your recipe through soapcalc.net without the castor and it should be a fairly hard bar already. You should really figure the castor into your recipe and then run it through the calculator at 5-7% superfat so that your recipe will be more accurate. Adding the castor at the end doesn't mean it will be what is used for superfatting because the lye will take what it wants. You have a good recipe even without the castor but if you wanted to add it, I would cut the coconut back to 25% and add 5% castor. Your bar will be a little softer, but it will be more conditioning.
Did you completely melt & stir your palm oil before measuring it? If not it could have seized because that batch had an excess of stearic acid from the palm oil. I've added salt (up to 1 tsp/# of oil) to my lye water and haven't had a problem with seizing. Maybe soapbuddy has other suggestions.
