At least a few of us here on SMF find that single-oil soaps, or soaps that are made primarily of a single oil (e.g., 70% or more) tend to need a longer cure before they are nice to use.Thanks. I let my Aleppo soap cure for at least 6 months and a year is better, but most other soaps I make are cured for about 8 weeks before I sell them. I haven't made salt bars but it's helpful information in case I do try.
Combinations of oils can become more than the sum of their parts once saponified. The one example that comes to mind is that they become a "eutetic mix" where the melting point of the mix is lower than its constituents. It's probably something analogous going on with curing mixed oils, rather than singles.