Do I need to add a preservative to my soap?

If you are making your soap properly (that is, without a ridiculously high superfat percentage, and ensuring you’re measuring & calculating correctly)—no.

Soap has a high pH because it is made from lye, which has a very high pH. This high pH wards off bacterial growth. The high pH of the soap will not wear off over time.

If you superfat your soap much about 7%, you may encounter rancidity (the excess oils in your soap will oxidize) or DOS (deadly orange spots). The best way to avoid this is by not superfatting your soap above 7%.

Something else that can interfere with the shelf life of your soap is adding acid to lower the pH (I’ve read about people doing this for shampoo). I’ve never tried it myself, but logically speaking, lowering the pH of the soap means its pH may no longer be high enough to ward off bacterial growth.

Posted in: Preservatives

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