Learn soap making
Cold process soap is oils plus a lye solution, stirred until it thickens and left to cure. The chemistry is unforgiving about measurement and relaxed about almost everything else.
Before anything else: lye safety
- Gloves and eye protection, every time. Sodium hydroxide burns skin and eyes.
- Always add lye to water, never water to lye. The reverse can boil violently and erupt out of the container.
- Mix somewhere ventilated. The solution briefly gives off fumes and heats to near boiling on its own.
- Keep children and pets out of the room while you work.
- Use heat-safe containers - stainless steel, heavy plastic marked #5, or heavy glass reserved for the purpose. Never aluminium; lye attacks it.
- Keep vinegar and running water nearby, and know where they are before you start.
What you need
- A digital scale that reads to 1 gram or better. Everything is weighed, never measured by volume.
- Sodium hydroxide (NaOH) for bar soap, or potassium hydroxide (KOH) for liquid soap.
- Your oils and butters.
- A stick blender - hand-stirring works but can take hours.
- A mold. A lined loaf pan is a perfectly good start.
- A thermometer, and a heat-safe jug for the lye solution.
The basic method
- Run your recipe through the calculator and write down every weight.
- Weigh the water, then weigh the lye separately. Add the lye to the water, stir until clear, and let it cool.
- Melt your hard oils, then add the liquid oils. Aim for both lye solution and oils somewhere around 90-120°F (32-49°C).
- Pour the lye solution into the oils and blend in short bursts until the mixture thickens to trace - thick enough that a drizzle leaves a mark on the surface.
- Stir in fragrance, colorant, or additives, then pour into the mold.
- Unmold once firm - often around 24 hours - and cut into bars.
- Cure on a rack with airflow for four to six weeks, longer for high-olive recipes. Cured soap is harder, milder, and lathers better.
The calculator's Recipe Insights estimate trace speed, unmold timing, gel phase, and cure length for your specific blend.
Where to start
The Classic Trinity in the recipe library - olive, coconut, and palm in balance - is the usual first batch: forgiving, quick to trace, and it makes a genuinely good bar. Make it once as written before adjusting anything.
Once you're comfortable, change one thing at a time and watch what the quality scores do. That's how the numbers stop being abstract.
Open the calculator →Guides, videos, and links
Hand-picked tutorials, supplier links, and video walkthroughs are being collected here.
This is an overview, not a substitute for careful reading and your own judgement. Soap making involves caustic chemicals; work at your own risk and verify lye amounts independently.