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Cold process soap for beginners
Cold process (CP) soap is made by combining fats and oils with a lye solution. The lye — sodium hydroxide (NaOH) for bar soap — reacts with the oils in a process called saponification, turning two things that are not soap into soap plus natural glycerin. "Cold" simply means you don't cook the batch; the reaction generates its own heat and finishes over the following days and weeks. It's the most popular method for handmade bar soap because it gives you full control over the recipe and a smooth, hard bar.
Open SoapLog — free →What you need
A handful of dedicated tools, kept separate from your kitchenware:
- A digital scale accurate to 1 g — soap is made by weight, never by volume
- Lye (NaOH), distilled water, and your oils (e.g. olive, coconut, palm or a butter)
- A heat-safe pitcher for the lye solution and a bowl for the oils
- A stick blender, a thermometer, a silicone or lined mold
- Safety gear: goggles, chemical-resistant gloves, long sleeves, and good ventilation
The basic workflow
Run your recipe through a lye calculator first, every time, to get the exact lye and water amounts for your oils. Then: weigh everything; add lye to water (never water to lye) and let the solution cool; melt and combine your oils; bring both to a similar temperature (often around 100–120 °F / 38–49 °C). Pour the lye solution into the oils and blend to "trace" — the point where the mix thickens like thin pudding. Add fragrance and color, pour into the mold, and insulate.
After the pour
Unmold and cut after roughly 24–48 hours, once the bar is firm. Fresh soap is still caustic and harsh, so it must cure for about four to six weeks before use. Curing lets excess water evaporate and the bar harden, giving a milder, longer-lasting soap. Start small — a 500 g oil batch is plenty to learn on — and write down exactly what you did so you can repeat your wins and learn from any miss.