Fresh soap is finished soap? Not quite. Saponification — the chemical reaction that turns oils and lye into soap — takes a few hours. But before soap is truly gentle on skin, it has to cure.
What happens during saponification.
Oils and lye (sodium hydroxide) react and turn into soap and glycerine. We make soap cold — we don't heat the mixture, so more of the oils' beneficial compounds and the natural glycerine that hydrates the skin stay in it. The reaction itself completes in a few hours. The soap is “finished” in the sense that it's no longer alkaline enough to harm.
So why three weeks?
Because “finished” doesn't yet mean “gentle”. During curing, water evaporates from the soap: the bar hardens, lasts longer and dissolves more slowly. At the same time the chemical maturing finishes — the pH drops and the soap becomes kinder to skin. Young soap could still pull and dry it out.
Good soap can't be rushed. You can only wait until it's ready.
That's why we don't rush our soaps at MuSK.
We let the block set, cut it by hand with a wire and place it on the shelves. There the bar rests for 21 days. We pack it only when it's truly ready for you. That's why every batch is a little different — and why the soap you receive lasts longer and is gentler.
Next in the Soapery Myths series: why hand-cut soap is deliberately imperfect — and why that's a feature.
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