Teach Soap

I remain unsure about just why we need to add so much % of FO to CP soap.
My first question is (since I have never made HP but I know some of you have): does it take less % of FO for HP, because I assume you add it right at the end when saponification is complete. Or in other words is it the active lye that eats FO?

Secondly, why is it that just 1% FO in my shampoo or liquid hand soap (syn) gives a really strong aroma, but 5% in CP soap hardly competes with it?

The lye eats up some of the fragrance. Liquid soap is already made/saponified before you add the fragrance. Fragrance is also personal and some fragrances are stronger then others. Flashpoints come into play for HP soap. The lower the flashpoint, the easier the FO evaporates and thus fades.

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Irena
Closed minds are like faulty parachutes; they refuse to open.

A lot of that has to do with time and temperature. In traditional CP, the fragrance is added prior to the saponification process and therefore is subjected to the higher temperatures for a longer time. This cooks off many of the volatile oils in the fragrances.

In HP, since the soap is already saponified, even though the soap mixture may still be hot when the FO/EO is added, the reaction is over and the soap is only in the cooling off phase. This allows us to use less fragrance, but the heat will still cook off some of the scent.

In both cases the heat also can change the scent based on which elements of the fragrance cook off first.

For shampoo, lotion, etc where the FO/EO can be added after the product is cool, they require even less fragrance because there is no heat to cook off and change the fragrance.

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Great explanations, thanks