A few days to one week after you’ve made your soap you can unmould it and prepare it for the curing process. During the 4 to 6 weeks of curing the saponification will finish and the soap will become milder (the pH will slightly decrease) and harder (due to the evaporation of water). First put on your gloves, as the lye might still be active, and unmould your soap. You can check the pH of your soap with a pH meter or pH strips, however the strips are not always reliable. In the soap makers’ world you will hear of the zap test. The zap test is when you touch the soap with the tip of your tongue and if you get a light zap like from a 9 volt battery then there is still unsaponified lye in your soap. If your soap has gelled then it shouldn’t zap after 24 hours. If it hasn’t gelled it might zap up to 3 days. If your soap zaps after 4 days then it might have too much lye in it due to an incorrect formula or incorrect weighing of ingredients, so it might be unusable. If you have the formula and can recalculate the quantities, you can add the missing ingredients and rebatch it. If the soap doesn’t zap you can slice it in individual bars and let them to cure. You can use a knife, a soap cutter (straight as in the picture above or crinkled) or a wire cutter (soap or cheese cutter). Your soap should cure for 4 to 6 weeks, you can use it after 4 weeks but after 6 weeks your soap is even milder and harder. Exception makes 100% olive oil soap which needs to cure for at least 6 months, but better for 1 year. A harder bar will also last longer. What makes your soap harder and longer lasting?
- Water discount – less water to evaporate;
- High percentage of hard oils and butters;
- Adding salt to harden your soap.
How and where to cure your soap?
- In a place out of reach of children and pets;
- Not in direct sunlight as it will affect the quality of your soap (fragrance and colour);
- Align the bars next to each other but not touching, so they don’t get stuck to each other and have enough spacer;
- Not in extreme temperatures (too hot or cold), ideally around 24 degrees Celsius/77 Fahrenheit;
- In a dry place;
- Turn the bars every few days so they can lose moisture from all sides and won’t warp.
After the soap is cured keep them in paper bags or cardboard boxes so it can breathe, otherwise it might grow mould!