No, an O level is more like a modern A level. So I was informed by my son when he did some O level papers during his A level course - and that was 5 years or so back.
The basic principal of soaps (and detergents) is to have one end water soluble, and the other end oil soluble. Wikipedia's quite good:
Calvin Sambrook coughed up some electrons that declared:
IIRC, strong alkali and fat/oil, eg: caustic soda + veggie oil => soap + glycerine
That's why cheap crap crude soaps don't do your skin any favours as they are
Animal fat can be used too.
Human fat could also be used (cf Fight Club)
I expect in the old days, it was made from a.n.-other-random-fat and lye (from wood ash) but I'm guessing. I know lye was a popular alkali as everyone had loads of wood ash going spare.
Here's an interesting article:
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"Fish oil soap" - erk! Wouldn't wash with that and expect to pot the red that night.
But I really *didn't* know grease involved soap. I thought it was just various fractions of distilled crap. Learn something every day...
Likewise. It leaves me wondering something else. Before reading this thread, I'd assumed that (like vaseline) grease was just a particularly thick petrochemical -- or a mix, to get the right properties. What is it that makes doing it that way impossible (or at least, makes making something that eventually dries out a better choice)?
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