I appreciate the anecdotal evidece for one. And the fact that you just answered several of my other questions as well. That's amazing.I've used sodium lactate, salt and bees wax for a harder bar. Then I found out that what I really wanted was a bar that lasted longer, not just harder (as in faster out of the mold and can cut earlier). All three cut the lather to some degree.
When I found out what I wanted was longevity, I got rid of most of my coconut oil and started adding rice of some sort to my soaps. I'm down to one bar of @Dawni 's triple rice soap so will be doing another couple of batches this month. It makes a lot of difference in the longevity of my soaps. This time I will be making ice cubes from the rice water and rice puree, so I have that part made...sort of like master batching my lye water. And I love the feel of the lather on my skin better than I did before going to rice.
I finally bought some sorbitol and will be trying that to increase the bubbles, but since I already like the feel of the lather, the sorbitol is only for my grandson who loves bubbles, not lather.
I was gonna ask another question about longevity, since some oils are more soluble others, regardless of how hard they are. What are some ways you increase longevity without sacrificing other values?Coconut oil (high in Lauric acid) creates a hard bar, but is very soluble, so the soap bubbles well, but gets used up faster.
Fats high in palmitic and stearic create longevity - i.e, yes they do harden a bar, but are not very soluble ( they're not there to promote lotsa bubbles) and thus they last longer.