Who cares about INS value?

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OWU Soaps

Mar 12, 2023
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I'm having trouble wrapping my brain around how to use INS, or if I should. It seems like I can always get a really high INS if I add a bunch of Palm Kernel Flakes and/or Coconut oil, but this always gives me a cleansing value higher than I want. I've read some articles that state it's a good idea to keep it above 145 but not to get wrapped up in searching for a 160-ish value. I was wondering if any of y'all could give a little insight into how you use INS in your process, or if it's not helpful. Thanks!
Nah, no need to worry at all about INS value. That is an outdated metric that is more important to large-scale commercial soap makers. Focus on getting the soap qualities that you want, remembering that "cleansing" actually means "stripping oils from your skin and making it dry." In other words, the suggested cleansing range in soap calculators really isn't helpful at all. Most handcrafted soapmakers want to be at the very low end or even below the suggested cleansing range.
I've never paid any attention to it. I still don't really understand it even though I've read about it a lot on here. I just don't seem to retain any information if it's something that doesn't affect me/my soap. Interestingly though, my standard recipe has an INS value of 150 which is mid range so I guess that's a good thing?
Q: Who cares about INS Value?
A: I do! 😁

I use SoapCalc to formulate recipes. The more you use it and experience the result of your formulations the more you will learn about manipulating values when using different oils.

The Basic Trinity of Oils "starter formula" has an INS 157. It is good for all skin types with good hardness/ lather and conditioning values. I also look at the SAT/UNSAT ratio for a balanced bar. It is good for people like me who don't know much about the science of soapmaking. ;)

If you have a head for science, you're in the right place. Try browsing @DeeAnna 's SOAPY STUFF It is a treasure chest of knowledge and experience based on science. Well worth your time and effort.

That being said, I'm not "sciencey" at all. All I need are the Soap Quality Values to achieve whatever it is I want to make. I've been at since I made my first soap in 2003 at age 60. Experience plus knowledge of all things soapy helps!

HAPPY SOAPING! :computerbath:
I agree with AliOop. I've never in my 27 years of soaping ever even looked at those numbers because they mean squat to me. I get more value in testing my recipe by the way it feels on my skin after it's cured and what my testers tell me. To me the way a soap feels is 1000x better than what the numbers tell me, but that's just me.
INS is a one-number measurement used by commercial soap makers to quickly compare various blends of fats. This measurement was invented quite some decades ago, so I don't know if it's even still used in commercial soap making anymore.

The "ideal" INS value of 160 is something proposed by handcrafted soap makers, however. That "ideal" is totally unrealistic for me (and I suspect for many other soap makers).

The only way to get the INS that high is to use a lot more coconut (or other "cleansing" fats) than I want to use. There's no way I'm going to make soap like that all in the name of meeting a measurement that someone thinks is "best".

You can use INS as a guide if you want but it is just one number that's kind of ... one dimensional.
For example, a 100% lard recipe and second recipe with a blend of coconut and olive might have the same INS number. Both soaps might behave the same when making and unmolding the soap, but that's only part of the story. The lard soap will last a long time and will produce low amounts of dense long-lived lather. The coconut-olive soap will have a much shorter life in the bath and will produce a generous amount of fluffy lather.

So it doesn't make sense for a handcrafted soap maker to have a strong focus on INS. As an alternative you can evaluate the various fatty acid percentages in a proposed recipe. More numbers to deal with, that's true, but the fatty acid profile will also give you a more nuanced idea about what the soap will be like.

Here's the rest of what I have to say about INS and iodine value:
English: Iodine Number and INS | Soapy Stuff
French translation: L'indice d'iode et le INS | Soapy Stuff
Thanks a lot everyone. What I get from all of this is that it's a number that does provide some value, some information, but really only if we understand what that information is, which is definitely more nuanced than good bar/bad bar. Zany, thanks for directing me to DeeAnna's site. What a wealth of resources. And DeeAnna, I like your advice about evaluating the fatty acids. I think learning about these will give me a better understanding of what I'm actually doing to the soap when I tinker. A lot more value there then in something simple like INS.