Soap Hardness vs Insolubility

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This is the note I sent to soapcalc via their contact  form at contact.asp

Hello and thank you for your wonderful soap calculator. I have one question regarding the hardness factor. Is this a measure, as it says, of hardness or of non-solubility? It is always a mind bender for new soaping students to grasp that hard doesn’t necessarily mean longer lasting and before addressing this in an upcoming class (where we’ll use your calculator) I just wanted to get any feedback from you on it. My understanding is that the higher palmitic and stearic values contribute more to the non-solubility of the soap than the actual hardness value. I just want to make sure I am proving correct information.

Thanks so much,

Bunni Dot Com (Vaughan Healy)

This is the answer I received:

Hi Bunni,

It is my understanding that palmitic and stearic values will affect the solubility of the soap as well as the hardness. Hardness will reach a threshold where making it harder does not contribute to bar life, however to a point it can help keep the bar integrity and life. And yes, my mind still gets twisted up with this stuff from time to time.

Let me know if you have any other questions or would like anything further clarified. Good luck with the class!

Take care,