Beginner cold-process soap
Plain, hard bars from olive oil, coconut oil and shea butter. One batch makes 10 to 12 bars that last for months.
- Difficulty
- Beginner
- Time
- 1½ hours, then 4 to 6 weeks to cure
- Cost
- About $20 per batch, plus tools
- Region
- Anywhere
- Safety
- High: read the safety box first
This guide is a draft and hasn't been reviewed yet.
Cold-process soap is oils plus lye, stirred until they turn into soap. No lye is left in a finished bar: it is all used up in the reaction. That’s why the recipe has to be weighed exactly.
[AI illustration: a loaf of cream-colored homemade soap cut into thick bars on a wooden board]
What you need
Ingredients, by weight. Use a digital kitchen scale. Cups and spoons are not accurate enough for soap.
| Ingredient | Weight |
|---|---|
| Olive oil | 18 oz (510 g) |
| Coconut oil | 10 oz (283 g) |
| Shea butter | 4 oz (113 g) |
| Lye: 100% sodium hydroxide, with nothing else on the label | 4½ oz (128 g) |
| Distilled water | 9 oz (255 g) |
This leaves 5% of the oil unreacted, which makes a gentle bar. It makes about 2¾ lb (1.3 kg) of soap.
Check the recipe yourself. Before your first batch, type these oils into a free online lye calculator and confirm the lye amount. Get in the habit: never use a soap recipe you haven’t checked.
Equipment:
- Digital scale that reads in grams or tenths of an ounce
- Stick (immersion) blender
- Stainless steel pot for the oils
- Heat-proof #5 plastic or stainless steel jug for the lye water
- Silicone spatula and a thermometer
- A 3 lb (1.4 kg) loaf mold, or a lined cardboard box
- Goggles, gloves, long sleeves
Keep these tools for soap only. If you’re buying the scale and stick blender new, expect to spend about $40 more the first time. [placeholder: check prices at your local store]
Make it
- Get ready. Put on your goggles and gloves. Clear the counter. Send kids and pets out.
- Mix the lye water. Weigh the water into the jug. Weigh the lye into a separate dry container. Outdoors or by an open window, pour the lye into the water and stir until clear. It gets very hot and gives off fumes for a minute. Let it cool to 100–110 °F (38–43 °C).
- Melt the oils. Melt the coconut oil and shea butter in the pot on low heat. Take it off the heat and add the olive oil. Aim for 100–110 °F (38–43 °C).
- Combine. Pour the lye water slowly into the oils. Blend in short bursts, stirring between bursts with the blender off.
- Blend to trace. After a few minutes it thickens like thin pudding. When a drizzle leaves a trail on the surface, that’s “trace”. Stop blending.
- Pour. Pour into the mold, cover it, and wrap it in a towel for 24 hours.
- Cut. After 24 to 48 hours, with gloves on, unmold and cut into bars. Fresh soap can still irritate skin.
- Cure. Stand the bars on a rack with air around them for 4 to 6 weeks. Turn them now and then. Curing finishes the reaction and dries the bar, so it lasts longer.
[AI illustration: soap bars standing on a wire rack to cure, spaced apart]
If something goes wrong
- It never thickened. Keep blending in bursts for up to 10 minutes. Cool oils take longer.
- It seized like mashed potatoes. Usually from fragrance oils or hot oils. Press it into the mold anyway; it is still soap.
- White powder on top. That’s soda ash, harmless. Trim it or steam it off.
- Crumbly, greasy, or pockets of liquid. The measurements were off. Don’t use it. Throw the batch out, wearing gloves.
Going further
Once you have made this plain bar a few times, try adding essential oils at trace, or swapping some olive oil for other oils. Every swap changes the lye amount, so run every change through a lye calculator.