Iodine/INS numbers in soapcalc

Hi all,

I'm wondering if anyone can explain what the iodine and INS numbers mean in soapcalc? I did a little googling and it seems that, generally, higher iodine = faster spoiling and INS closer to 160 = better soap.

Are these numbers very important when designing a recipe? I'm new to soapmaking and I'm trying to come up with a recipe using the oils I have, and I'm getting very high iodine values (>70). I think it's because I'm using safflower oil, which I understand has a tendency towards spoiling, but I'd like to play with that oil a bit (since it's cheaper than olive oil and seems to have similar qualities).

What do you think? Am I totally deluded?

Oh, for reference, the recipe I'm considering using is
50% Crisco (new)
30% coconut
15% safflower
5% castor

(maybe 5-7.5% superfat)

Since you're just starting out, play around.
The first couple of batches are more about getting to learn the process than the outcome anyway. Keep it simple and cheap.

Make sure you write down everything down, to the smallest details.
Doing a lot of different test batches and making mistakes will give you more insight than soapcalc ever will

Iodine number is a measure of the polyunsaturated nature of the fat. Higher iodine number = More double bonds (more polyunsaturated).

INS is the Saponification Value in milligrams of KOH / gram of fat - Iodine number. It is a rough measure of how easy the fat will be to saponify and how hard the soap will be initially. Higher INS = easier to saponify & harder in the mold.

Both come out of industrial soap chemistry. INS was meant to be a quick "one number" method of evaluating fats for use in soap. It's the number I check rather than worry too much about iodine number. In industrial soap making, the goal is to create a soap that saponifies easily and is relatively hard right after saponification is complete. An INS inside the "recommended" range indicates a recipe that will most likely accomplish those goals.

INS can be useful to hand craft soap makers. A recipe that is too far out of the "recommended" range may be trickier to make. A recipe with a very high INS value may trace very fast. One with a very low INS may trace slowly or may be too soft to unmold quickly.

If you want more time to do fancy swirls or other decorative techniques, design a recipe with a lower INS value. If you are a beginner or a high volume soap maker, it may be wise to design a recipe that has an INS within the recommended range.

I think "the numbers" are useful, but most people don't take the time to really understand what "the numbers" really mean, so the common wisdom is that "the numbers" lie, or they really aren't useful, or the like. I agree that experimentation is important, but doing research before doing experiments is important too.

I think a lot of folks really "fly by the seat of their pants" when making soap -- just read all the posts on SMF from people frantically asking "what horrible thing just happened to my soap?", or the posters that bemoan the fact that they have only made one successful batch out of six, or the like. A few do go on to learn about their craft, but most will continue to flail around blindly and wonder why things don't work well for them.

So kudos to you, Magstang, for asking good questions and wanting to understand more about the soap making craft!

Dagmar is right about testing and taking notes. Those numbers are guides. Nothing works better than experimentation.

But, also - yes the safflower is raising the iodine number. For me, personally, a high iodine in soap gives me "shower-itch". I haven't had DOS in any of those soaps, but I do try to keep it under 60 now. But, your mileage may vary - I've seen lots of soapers who use high amounts of safflower.

As far as your recipe, it looks fine. I would make it without too much concern.

Only thing I would personally do to tweak your recipe more to my liking is lower the coconut oil to 20%-25% to reduce the "cleansing number". Add more Crisco to compensate. Yes, this will lower your INS to below the "recommended" range, but I wouldn't worry about that greatly -- you're reasonably close. Your superfat % is fine; pick a number and go with it.

But all this is just my opinion. Your original recipe will make fine soap, so YMMV.

Thank you, everyone, for your comments, and DeeAnna specifically- that was an extremely detailed and clear response! I'm a trained chemist, so I'm well-practiced in the art of taking notes. I just am very unfamiliar with this specific field. :think:

pamielynn, what do you mean by "shower itch?" I have extremely sensitive skin, so I'd rather not do anything that would be irritating. Can you elaborate?

Thanks again everyone!

@DeeAnna - Wow - so I know this post is old, but it was exactly what I was looking for! Thank you ever so much for your greatly detailed response!
(from a not-chemist who is trying to learn more about this fun hobby of mine!)

Deborah Long said:

@DeeAnna - Wow - so I know this post is old, but it was exactly what I was looking for! Thank you ever so much for your greatly detailed response!
(from a not-chemist who is trying to learn more about this fun hobby of mine!)

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I started soaping last August and the very 1st batch I ever made was extra virgin olive oil soap. then I went from there. I made a small batch and ran it through the soap calac. I used 10oz of oil and just followed the water on the soap calc. I then poured it in the 2 oz cups you get at Dollar tree for 1 for a pack of 10. after that I worked my way up to adding 1 % coconut oil etc always in small batches. Now the largest batch I've ever made to date was 3 lb oil batch. The most recent thing I learned was chealating thanks to this wonderful soapmaking forum.