Scent Almanac
Hot-process soap (crockpot)
Soap cooked in a slow cooker until saponification finishes, giving a rustic textured bar that's safe sooner and holds fragrance well because the scent goes in after the cook.
- Difficulty
- ●●●
- Time
- active 2–2.5 h · cut next day · cure 4 weeks
Safety first
- Wear chemical-splash goggles (not just glasses), nitrile or rubber gloves, long sleeves and closed shoes from the moment the lye container opens until the raw soap is put away.
- Mix lye solution in a well-ventilated spot: under a running range hood, by an open window, or outdoors. Don't lean over it. The fumes in the first minute sting the lungs.
- Always add lye to water, never water to lye ('snow falls on the lake'). Pouring water onto lye can erupt and splash boiling caustic liquid.
- Mix and hold lye in a heavy stainless steel or #5 PP plastic container, and stir with stainless or silicone. NEVER use aluminum, which reacts violently and gives off hydrogen gas. Avoid glass, which lye etches and can crack.
- Keep children and pets out of the room until the lye, raw soap and all tools are cleaned up and put away.
- Keep vinegar handy for wiping lye or raw soap off counters and floors. It is for surfaces only. For skin and eyes, use plain running water: flush for 15 minutes. For eyes, flush for 15 minutes and get medical help.
- Weigh everything (oils, water and lye) on a digital scale in grams. Never measure by volume.
- Run every recipe through a lye calculator before you make it, including this one and any time you swap an oil. The preset here opens in the app's lye calculator.
- Store lye sealed, labeled and out of reach. Raw soap stays caustic for a day or two, so wear gloves to unmold and cut it.
- Use a slow cooker you'll never cook food in again. Never use an aluminum pot or insert.
- Fill the slow cooker no more than halfway. Hot-process batter can foam up and overflow ('soap volcano'). Stir it down and keep the lid handy.
- Cooked soap is near 180–200°F (82–93°C) and sticky. It burns like hot sugar, so keep gloves and sleeves on through the cook and the mold.
Steps
- Check the recipe in the lye calculator and write down the weights. Put on protective gear and clear the room.
- In a ventilated spot, add the lye to the water (never water to lye) in a stainless steel or #5 PP container and stir until clear.
- Melt the oils and butters in the slow cooker on LOW.
- Carefully pour the lye solution into the oils and stick-blend to medium-thick trace.
- Cover and cook on LOW, checking and stirring every 10–15 minutes. It goes through stages: it may rise or separate at the edges ('champagne bubbles'), then look like applesauce, and finally become a glossy, translucent gel like petroleum jelly or mashed potatoes. This usually takes 45–90 minutes. Stir down any rise immediately.
- When it looks uniformly translucent, test a cooled pea-sized bit with a zap test or a pH strip. No zap, or a pH of 10 or under, means it's cooked.
- Turn off the heat and let it cool for a few minutes, then stir in the yogurt or sodium lactate (optional) and the fragrance. Adding fragrance after the cook keeps more of the scent.
- Spoon the batter into the mold in layers, pressing and banging the mold on the counter between spoonfuls to remove air pockets. Texture the top with a spoon.
- Let it cool and harden overnight, then unmold and cut.
- It's safe to use once it passes the zap or pH test, but cure it on a rack for about 4 weeks for a harder, longer-lasting bar.
NaOH138.7 g · 4.9 oz
Water (distilled)324 g · 11.4 oz
2.3 : 1 water to lye
Fragrance40 g · 1.4 oz
Batch weight1502 g · 53.0 oz
| Oil | % | Weight |
|---|---|---|
| Olive oil | 45.0 | 450 g · 15.9 oz |
| Coconut oil (76°) | 25.0 | 250 g · 8.8 oz |
| Shea butter | 15.0 | 150 g · 5.3 oz |
| Sweet almond oil | 10.0 | 100 g · 3.5 oz |
| Castor oil | 5.0 | 50 g · 1.8 oz |
Bar qualities
Hardness
35
Cleansing
17
Conditioning
61
Bubbly
21
Creamy
23
Iodine
64
INS
141
Green bands are the usual ranges for a balanced bar. Liquid soap, castile and salt bars fall outside them on purpose.
Lye safety: wear goggles and gloves. Add lye to water, never water to lye, in a heat-safe stainless or #5 plastic container, with good ventilation and no children or pets nearby. Always double-check a lye amount with a second calculator before you make soap.
If something goes wrong
- Soap volcano (batter foaming over the top)
- Turn it off and stir it down hard. Use LOW heat and fill the slow cooker no more than halfway.
- Batter too thick to mold (lumpy, full of air pockets)
- Stir in yogurt or sodium lactate after the cook, use the full water amount, and bang the mold firmly between layers.
- Still zaps after cooking
- Not fully cooked. Keep cooking and stirring 15 minutes more, then test again. If it still zaps, recheck the recipe and scale.
- Fragrance faded
- It was added while the batter was too hot. Let it cool a few minutes first, and add it after the cook.
- Dry, crumbly bars
- Overcooked or too little water. Cook only until translucent and use the calculator's full water amount.