Rancid oils

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New Member
May 13, 2015
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Hi, I have a box full of rancid/expired oils, and would like to use it up instead of throwing it out. If i were to do a hot process superfat at 0% for the expired/rancid oils, I understand that the soap might be dry to the skin. I was wondering if i could add in my cocoa butter ( its not expired) to the soap batter as a addictive after I've trace it or should i add it after its cooked? Should I add 5% cocoa butter of the total oil used? In the soap calculation, i will not include cocoa butter in the calculation. Is that correct? Thank you so much.


Well-Known Member
Feb 6, 2022
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BC, Canada
For hot process you add your SF (superfat) after cook. Otherwise the Lye will eat from ALL the oils randomly. They recommend a 28% lye to water concentration to make it more manageable when you are putting it into a mold. The other trick is to add Yogourt at the end to help mold it. 1 tbsp per pond of oil, and warm it so it doesn't make your batter seize.

Making soap from rancid oils is probably a bad idea, especially if it's an oil like shea that doesn't fully saponify (all the oil doesn't change to soap when making soap); the other one that I know of is cocoa butter, but there's probably others too.
Apr 5, 2017
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I have washed oils and fats to remove the impurities that make them smell rancid. I saved several gallons of palm oil through washing and two years later the PO is still pristine. I saw the method mentioned in a commercial soapmaking book from the early 1900s, but it is essentially the same as rendering tallow. It should work for liquid oils as well. It’s pretty simple to mix up one part salt to nine parts water and simmer the oil in the brine. Check out the end of this page on @DeeAnna ‘s website. Rancidity and DOS | Soapy Stuff

Rancid oils may rice or otherwise behave badly in your soap recipe. The smell may also linger. Here’s a post from @DeeAnna about problems with oils as they age. Quick question - stale oil
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