Making your own soap sounds intimidating until you realize it's really just chemistry plus a little patience. Combine oils with a lye solution and a reaction called saponification turns them into soap and natural glycerin. Do it “cold process” — without external heat — and you get a hard, long-lasting, fully customizable bar you made from scratch.
This guide covers everything a first-timer needs: staying safe, choosing your oils, and the step-by-step. And because the most important part — getting the exact lye amount right — is the part you can't eyeball, we'll show you where Lyewise does the math for you.
Prefer to watch? We filmed the whole process start to finish. Watch: How to Make Cold Process Soap →
Equipment: a digital scale (everything is measured by weight), stainless steel or heavy plastic bowls, a stick blender, a mold, a thermometer, goggles and gloves. Ingredients: your oils and fats, sodium hydroxide (lye), distilled water, and optionally fragrance or essential oils, colorants, and additives.
Every oil brings a different personality to your bar because each is made of different fatty acids. Learn what they do and you can design a bar for exactly what you want:
A friendly starter blend: olive for gentleness, coconut for cleansing and lather, palm (or tallow) for hardness, and a touch of castor for bubbles. The catch: change any oil and you change how much lye the recipe needs and how the bar behaves. Drop your oils into Lyewise and it calculates the exact lye and water instantly, predicts hardness, cleansing, conditioning and lather before you mix, and includes a searchable oils encyclopedia.
1. Nail down your recipe. Decide your oils and batch size, then get your exact lye, water, and superfat. Run it through Lyewise so a typo doesn't ruin a batch or leave it lye-heavy.
2. Gear up and prep. Goggles and gloves on. Weigh every oil, melt the hard oils and butters, then stir in the liquid oils and bring them to about 100–110°F.
3. Make the lye solution. Weigh water and lye separately, add the lye to the water (never the reverse), stir until clear, and let it cool to roughly 100–110°F. Mind the fumes at first.
4. Combine. When oils and lye solution are both around 95–110°F and within about 10 degrees of each other, pour the lye solution into the oils.
5. Blend to trace. Pulse with the stick blender until it thickens like thin pudding and leaves a faint trail on the surface — that's trace.
6. Add the extras. At trace, stir in fragrance, color, and additives, working fairly quickly.
7. Pour and set. Pour into the mold, tap out bubbles, cover, and wait 24–48 hours.
8. Unmold and cut once firm.
9. Cure. Rest the bars on a rack with airflow for 4–6 weeks so they harden and mellow. Worth the wait.
Superfat — intentionally leaving ~5–8% of oils un-saponified so no active lye remains and the bar feels moisturizing (Lyewise sets this for you). Water discount — a bit less water gives a harder bar that unmolds faster. If a batch ever misbehaves, Lyewise has a built-in troubleshooting assistant.
Pick your oils and batch size, run them through Lyewise for exact lye and water plus a bar-quality preview, follow the steps, and cure. Lyewise runs in any browser and installs to your phone, so your recipe is right at your workbench — and it's $1 a year, cheaper than a single bad batch of wasted oils.
Start your first recipe in Lyewise →
Rather see it done? Our full step-by-step video walks through an entire batch from oils to cut bars.
Lyewise is an estimating and planning aid for soap makers. Soap making involves sodium hydroxide (lye), a caustic chemical — always verify your figures and follow proper safety precautions. See our Terms of Service for details.