What sort of preservatives should I use for my Cold Processed soap formula? How long is the shelf life using these preservatives? Will humidity affect my bar?
Preservatives: A properly saponified and formulated bar of soap will not require preservatives.
The only time he might require a preservative is if the Superfat value is too high, leaving a high percentage of unsaponified oils.
Recommend staying somewhere around a 4%-5% superfat.
Humidity: Again, a high superfat will have problems, mold, oxidation, etc.
Shelf Life: Again, a high superfat will have a shorter shelf life. A properly saponified bar should last four years or more. We have soap that has lasted six years sitting in a high humidity un-air-conditioned space.