If you have made cold process soap, you have probably heard the instruction: “Let it cure.” But curing is more than simply waiting for a bar to become hard enough to hold.
What is curing?
Curing is the period after the soap has been unmoulded and cut when it continues to lose water and its physical characteristics develop. The exact experience depends on the formula, environment, bar size and storage conditions.
Curing and saponification are related—but not identical
Saponification is the chemical reaction in which the oils and sodium hydroxide form soap. A properly formulated and processed cold process soap can complete most of this reaction relatively early, but the finished bar still benefits from time to dry and develop its final characteristics.
What changes during the cure?
Water evaporates
As moisture leaves the bar, the soap generally becomes firmer and more resistant to wearing away quickly in use.
The bar becomes easier to use
A well-cured bar usually has a more developed texture and can provide a better user experience than a freshly cut bar.
The formulation settles
Time can allow the finished soap to develop a more stable sensory character, although the exact result varies with formulation and ingredients.
Can you use soap before the full cure?
A soap maker should follow the curing guidance appropriate to the specific formulation and process. Early use may produce a softer, faster-wearing bar, and safety should never be compromised by rushing the process.
How to make curing easier
- Cut bars consistently so they cure at a similar rate.
- Leave space between bars for airflow.
- Label batches with the date they were made.
- Rotate or rearrange bars if needed for even airflow.
- Do not judge readiness by hardness alone.
Patience is part of soap making
One of the joys of handmade soap is learning to respect the process. The moulding and cutting happen quickly; the best part of the work often happens quietly afterward.