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question about using old oils


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i haven't soaped much lately and now find myself with some rather old oils. they all still smell and look fine.

my question is this: once they become soap, does the fact that they were old affect the soap life, and if so how much, i.e. will the soap go bad quickly?

part of me thinks yes, part of me isn't sure.



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Check the shelf lives for the oils. Most are ok even up to several years and some only for months. The storage affects the quality as well. Stored in a cool area or a refrigerator should insure the oils are ok for soaping. If they don't smell rancid or look discolored; they ought to be ok. IMHO.


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I don't think the older oils are more likely to make the soap go bad except for the softest ones.

Rancidity just means that the oil molecules are breaking down into glycerin and free fatty acids. The free fatty acids saponify immediately, so when an oil has decomposed slightly over time it will probably just trace faster. You see this effect sometimes with pomace olive oil, which is effectively a little rancid compared to regular olive oil even when you buy it fresh.

Rancidity and oxidation don't always go hand in hand. You can get into problems with stability when the fatty acids in the oil oxidize, which is more likely to happen with unsaturated oils. It's not a bad idea to keep monounsaturated liquid oils like olive cool if you can. Polyunsatured oils are probably best avoided altogether, especially when they've been sitting around a while.

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hi again top,

the olive oil is in a fairly cool place which will definitely get warmer as summer approaches. i guess i'll make some room in the refrigerator before the really warm weather arrives here in jersey. maybe i should just buy another one!

after reading your reply i took a quick look on the web and now understand why high oleic sunflower and safflower oils are ok for soap and the regular sunflower and safflower are not a good idea.

i always learn something from your posts top, this time you peaked my curiosity about mono and polyunsaturated fats and that led to checking the diff between linoleic and oleic acids.

thanks once again for the time you always take to give technical information, i for one (and i'm sure there are many others) really appreciate it!


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I always taste questionable oils too, they can smell okay but taste off sometimes.


Not all places sell food grade oils. Some sell them as manufacturing quality, I don't know if that makes a different but I wouldn't be tasting any that have that on the box just in case.


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