Yes,
cleansing in this context seems to me to be a stronger word than
clean. I think of cleansing in soap as 'stripping' or to give it a stronger analogy I think of it as similar to 'ethnic cleansing' Not to put a political bent to the conversation, just to point out that in this respect cleansing in the case of soap is meant in the stronger sense than simply 'to clean'.
For me I find that I prefer a lower cleansing number, although I actually do like one soap I make with a high cleansing number, but it also has other ingredients that seem to counteract the drying properties that go along with that high cleansing number. But so far, it seems to be the only one (with a high cleansing number) that doesn't dry out my skin when I use it regularly.
I used to try to fit cleansing into that SoapCalc range but with many recipes it just dries my skin out and I get surface cracks that catch on my knit sweaters and whatnot. So it was big trial and error for me.
An example of a very mild soap that has long been considered the best soap around is Castile soap. But it's cleansing value is 0 and it certainly gets the skin clean.
Those numbers come from an unattributed source apparently from the 1930's which Dr. Robert McDaniels outlines in his book, Essentially Soap (2000). I would love to see the original article about INS, mentioned in this
blogpost. The blogger apparently found the original, but I have no idea where or how.
I've only been soaping for a year and a half, so I had no idea that the use of INS in
lye calculators was so 'new'. But I'd sure like to hear more about the historical side of those calculations and when and how they became such an 'industry standard' or 'industry guideline' to be more exact.