INS was 160

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whitewitchbeauty

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Do i win a prize or get a sticker? :) I made some patchouli & rosemary CP soap and noticed my INS in soap calc was 160. I read that is a good thing but on Brambleberry i read it doesn't mean jack. Darnit i was hoping it meant i made a great batch of soap. Im not sure if INS means anything significant.
 
INS is the saponification value minus the iodine number. Iodine number is a measure of the unsaturated bonds in the fats. In other words, more liquid oils -> more unsaturation -> higher iodine number OR lower INS number. The more unsaturation, the greater potential for a softer soap and greater chance for DOS. Obviously, a high iodine number doesn't absolutely mean the soap will be soft or get DOS; it's just an indicator.

Both iodine number and INS are ways to evaluate a fat mixture for ease of saponification, initial hardness for ease of unmolding, and the shelf life of the soap. They are values originally created for quickly evaluating blends of fats for use in large scale commercial soapmaking. They are not quite so critical for the handcrafted soapmaker who is less concerned about churning out mass quantities of soap.

Rather than focus on the iodine or INS numbers, some people keep the sum of linoleic and linolenic acid under 15% to help guard against DOS and softness. Or they have a rule of thumb about limiting the polyunsaturated oils such as canola, corn, soy, sunflower, safflower, etc. to a modestly low % in their recipes. Some watch the iodine number or INS value instead.

See also: http://www.soapmakingforum.com/showthread.php?p=320350

ETA: I made five batches of soap this weekend. The INS ranged from 137 to 155. Linoleic + linolenic amounts ranged from 4% to 6%. All were firm enough to unmold in 12 hours, and they will be fine to cut today. The little sample bars I poured from one batch didn't go through gel, so they're somewhat softer than the main loaf made from the same batch, but I still was able to ummold these little bars just fine.
 
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Rather than focus on the iodine or INS numbers, some people keep the sum of linoleic and linolenic acid under 15% to help guard against DOS and softness. Or they have a rule of thumb about limiting the polyunsaturated oils such as canola, corn, soy, sunflower, safflower, etc. to a modestly low % in their recipes.

I see you mention softness as one property of Linolenic and Linoleic acids, but isn't this property also given by oleic acid too? (Olive oil, sunflower/safflower HO).
 
Carbon chain of Oleic acid (C18:1)
Carbon chain of Linoleic (C18:2)
Carbon chain of Linolenic (C18:3)

Notice how Oleic has only 1 after the 18, while the other two have more? That particular number after the 18 represents the unsaturated places in the carbon chain. The higher that number, the softer the soap will turn out. So, in effect, a 100% HO Sunflower oil soap (with a higher oleic content) will turn out a harder soap than a 100% regular sunflower oil soap (which has a much higher linoleic content).


IrishLass :)
 
So much to learn, thanks. I wish i could meet with someone locally and soap together, or just talk soap. :) I'm thankful for the internet! Somehow this has become a big stress reliever and therapy for me. I love learning and there is so much to soap making it will take years to master, which i invite with love :)
 
So much to learn, thanks. I wish i could meet with someone locally and soap together, or just talk soap. :) I'm thankful for the internet! Somehow this has become a big stress reliever and therapy for me. I love learning and there is so much to soap making it will take years to master, which i invite with love :)

Amen to everything you wrote. I'm incredibly grateful for those willing to share their knowledge here; there's so much to learn and I'm soaking it all in, as much as this old brain will allow at any given time.
 

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