Cream soap

Method

1. Get ready

   Put on sealed goggles, gloves and long sleeves, and keep them on until the soap has rested. Weigh 150 g stearic acid, 125 g coconut oil, 50 g shea butter, 125 g olive oil, 50 g castor oil and 50 g glycerin into a slow cooker of 3.5 litres or more, 300 g distilled water into a heat-proof jug, and 18.0 g sodium hydroxide and 84.2 g potassium hydroxide flakes into two dry containers; close the flake tub at once.

2. Make the lye solution

   At an open window, stir the sodium hydroxide and then the potassium hydroxide into the water a little at a time, never the water onto the lye. It fizzes and gets hotter than a sodium hydroxide solution; keep it away from aluminium and let it cool below 82 °C (180 °F).

3. Melt the fats hot

   Melt the stearic acid, coconut oil and shea butter on high, stir in the olive and castor oils, then turn the cooker to low and hold the fats at 70 to 75 °C (158 to 167 °F). Stearic acid sets at about 55 °C (131 °F), so keep well clear of it; the glycerin sits apart from the oils for now, which is fine.

4. Add the lye

   Pour the lye solution into the fats in a thin, steady stream, stirring with a spatula. The batter turns milky white and may look grainy as the stearic acid becomes soap the moment the lye reaches it.

5. Blend to the honey stage

   Stick blend in short bursts. It goes from a thin milkshake to lumpy, watery mashed potato and then to a smooth, heavy cream like set honey; blend until it stays smooth when you stop.

6. Cover and cook

   Put the lid on and cook on low for 3 to 4 hours, checking every 30 minutes and stirring it down if it rises. After about an hour it is too stiff to stir, so cut into it with the spatula and turn it over in chunks so it cooks evenly.

7. Cook until translucent

   It is done when the whole mass is golden and translucent, like petroleum jelly, with no opaque patches when you turn it. If you have phenolphthalein, a drop on a smear should turn only a faint pink that creeps in; an instant, vivid magenta means another 30 minutes.

8. Rest it for a day

   Turn off the cooker and leave the soap covered in the pot for 24 hours to cool and firm.

9. Whip it

   Break the soap into a large bowl, add about 100 g of the hot distilled water and beat it with a stick blender or a hand mixer. After a minute or two it suddenly turns paler, lighter and fluffier; keep going until it is smooth.

10. Soften it to taste

    If it is firmer than you want, beat in more hot water 25 g at a time, letting each addition disappear before the next, up to 250 g in all. Aim for a cream that holds a soft peak and scoops cleanly, a little heavier than whipped cream; water can go in later but never comes out.

11. Scent it

    Beat in the lavender and geranium oils for the last minute of whipping, then leave the bowl covered for a few hours and judge the texture again.

12. Let it settle

    Pack it into a tub with a tight lid, stir it once a day for a week, then leave it a second week. Some of the air escapes and it turns denser and pearlier; if it has gone too runny, leave the lid off for a day.

13. Fill the jars

    Fill jars, tubes or pumps from a piping bag, or from a strong food bag with a corner snipped off, filling by volume because the air in it changes the weight. Fill it cool: warming cream soap stiffens it.

14. Keep it clean

    Scoop it with a clean, dry spoon rather than fingers, and keep the lid on or the top dries out. It is about half water, so to keep it long, or to sell it, it needs a preservative that works at pH 9 to 10.