Saponification is the chemical reaction that turns oils and lye into soap — this is mostly complete within 24–48 hours after pouring. Curing is the slower process of water evaporation and crystal structure formation that hardens the bar and makes it milder. These are two different things.
After cutting, place bars on a curing rack with at least 1/2 inch of space between them for airflow. Keep them in a cool, dry, well-ventilated area out of direct sunlight. Turn bars every few days during the first week for even drying.
Minimum cure times by recipe type: standard mixed-oil CP soap: 4–6 weeks. High olive oil soap: 6–8 weeks. Pure Castile soap: 6–12 months. Salt bars: 4–8 weeks. The longer the cure, the harder, milder, and longer-lasting the bar.
To test if a bar is cured: weigh it weekly — when weight loss stabilizes, the bar is nearly cured. A well-cured bar feels hard and dry, lathers well, and is mild on skin. An under-cured bar feels soft, dissolves quickly, and may be slightly more alkaline.
Store finished bars in a cool, dry place with good airflow. Do not store in airtight containers long-term — soap needs to breathe. For storage longer than 6 months, wrap bars in paper (not plastic) and keep out of direct light to preserve scent and color.