Understand the bar before you make it.

Two processes, one reaction

Soap is what happens when oils meet an alkali. Sodium hydroxide turns fats into soap within 24–48 hours. What differs is where it finishes.

Cold process soap is blended to trace and saponifies in the mold. You choose whether it goes through gel, and it needs a full cure of at least 4–6 weeks. Hot process soap is cooked on low heat until it looks like waxy mashed potatoes. Superfat oils, delicate scents, milk and honey go in after the cook, and the bars need only 1–2 weeks of hardening.

What each oil brings

Every oil changes the bar through its fatty acids. The book's balanced bars are roughly 28–30% coconut, 15–25% butters, 44–47% olive and 2–5% castor.

The numbers are predictions, not laws. To change a bar, change the oils, never the lye.

The gel phase

Fresh soap heats itself. In gel phase it reaches 54–82 °C and turns semi-translucent, giving brighter colors and a harder bar. Insulate to encourage it; chill to prevent it. Milk soaps and layered designs are made without gel.

Cure times from the book

A sample from the book: Rosemary & Citrus Luxury Bar

A multi-oil cold process bar with a rosemary-infused post-trace superfat and a spirulina swirl. About 500 g, 6% superfat.

Key steps: bring lye and oils to a deliberately warm 43–46 °C so the butters stay fluid, blend to medium trace, add the macerate, then the essential oils. Split, color half with spirulina, swirl, spray with alcohol, gel in a warm switched-off oven, and cure 6–8 weeks.