The fragrance disappeared

A bar that smelled wonderful when it was cut and smells of nothing when it is ready to sell.

Strong in the pot, gone at six weeks

Almost universal with essential oils and common with cheaper fragrance oils.

The instinct is to double the dose, which produces a bar that is harsh at first, may accelerate the batch, and fades anyway.

What happened

The alkaline environment. Soap is strongly alkaline while it saponifies, and many aroma compounds do not survive it chemically. This is the main cause and no dose fixes it.

Heat, during gel, which drives off volatiles.

Evaporation over a six-week cure with air moving past the bars, which is exactly the condition the cure requires.

Light top notes being inherently fugitive: citrus is the classic and it disappears almost entirely unanchored.

Anchoring

A base note that holds lighter notes: patchouli, cedarwood, benzoin, vetiver.

Clay, which many makers use as a fragrance anchor and which also colors gently.

Blending a fugitive oil with a tenacious one rather than using it alone.

These work, and they change the scent, which is a trade rather than a fix.

Choosing better

Buy fragrances stated as suitable for cold process soap, and ask the supplier for performance notes.

Good suppliers say whether an oil holds through cure, and that is a useful piece of information about a fragrance.

Use a proper rate rather than guessing, by weight, as a percentage of oils.

And judge the scent at the end of the cure rather than at the cut, because that is the product the customer smells.

References