How Long Does Soap Need to Cure? Cure Times for Every Type of Soap

The Short Answer

Most cold process soap needs 4–6 weeks of cure time. Hot process soap can be used after about a week but improves with 2–4 weeks. High olive oil soaps such as castile need 6 months or more. Liquid soap does not need a cure at all.

Cure Times by Soap Type

• Cold process bar soap: 4–6 weeks
• Hot process bar soap: usable after about 1 week, best after 2–4 weeks
• Castile (100% olive oil): at least 6 months, ideally 12
• Bastille (70%+ olive oil): 8 weeks or more
• Salt bars: at least 8 weeks, and they keep improving for months
• Goat milk and other milk soaps: 4–6 weeks
• Liquid soap (KOH): no cure needed once the paste is fully cooked and diluted

Why Soap Needs to Cure

Most of the chemical reaction between lye and oils (saponification) is finished within 24–48 hours. Curing is mainly about water. Fresh soap can be 25–30% water; as that water evaporates the bar gets harder, milder and longer lasting, and the crystal structure of the soap settles so it lathers better. An under-cured bar is soft and dissolves quickly in the shower.

How to Cure Soap Properly

• Cut your loaf into bars and stand them on a rack or slatted shelf with space between each bar
• Keep them in a cool, dry room with good airflow, ideally 18–21°C
• Keep them out of direct sunlight, which can fade colours and speed up rancidity
• Turn the bars every week or so for even drying
• Avoid humid rooms such as kitchens and bathrooms

How to Tell When Your Soap Is Ready

The most reliable test is weight. Weigh one bar each week and write it down. When the weight stops dropping, the water has gone and the bar is fully cured. Your batch records should also show the date each batch was made and when it will be ready, so you never sell or gift a bar too early.

Track cure dates with the free LatherForge soap calculator app →

Can You Speed Up the Cure?

Using less water in your recipe (a stronger lye solution) shortens cure time a little, and hot process gives a usable bar sooner. But there is no real shortcut for a high olive oil bar. Warm rooms and fans help with airflow, but heat and direct sun can do more harm than good.

Can I use soap before it has cured?

Cold process soap is usually safe to use after 48 hours once saponification has finished, provided the recipe was correctly calculated. It will be soft, wear away quickly and may feel harsher than a cured bar, so it is best kept for personal testing rather than selling or gifting.

Do you need to cure melt and pour soap?

No. Melt and pour base has already been saponified by the manufacturer, so it can be used as soon as it has set. Wrap it promptly, because melt and pour bases can attract moisture from the air and "sweat".

Does hot process soap need to cure?

Hot process soap is safe to use once it has cooled and hardened, usually within a day or two. A 1–4 week cure still helps: the bar gets harder, milder and longer lasting as excess water evaporates.

Why does castile soap take so long to cure?

Olive oil makes a soft bar that holds on to water and lathers slowly at first. Over 6 to 12 months the bar hardens and the slimy lather becomes creamier, which is why castile makers cure for much longer than the usual 4–6 weeks.

Can soap cure for too long?

Most bars only get better with time. The risk with very long cures is rancidity, which shows up as orange spots and an off smell, especially in recipes high in soft oils or with a high superfat. Store curing bars somewhere cool, dark and airy and use them within a year or two.