Daniel Ashworth
Why handmade soap earns its place on the sink
Cold-process soap is one of the most rewarding crafts you can take up at the kitchen table. The ingredient list is short — olive oil, coconut oil, water, lye and a pinch of natural clay — yet the result is a proper, long-lasting bar that lathers well and looks handsome beside the basin. You control what goes in, you can scent and colour it however you like, and you cut down on plastic bottles at the same time.
It is not a five-minute project, though. Cold-process soap needs a careful hand with sodium hydroxide, and then four to six weeks of quiet curing before the bars are at their best. Plan for one batch to see you through a good few months.
Safety first: lye is not to be rushed
Sodium hydroxide — sold as caustic soda in hardware shops — is the alkali that turns oil into soap. It is perfectly manageable, but it demands respect. Work in a well-ventilated kitchen, keep children and pets out of the room, and never let the two of you be distracted.
- Wear rubber gloves, safety goggles and long sleeves. An apron saves your clothes from splashes.
- Always add the lye to the water, never water to lye, and stir gently. The mixture will heat to around 70°C within seconds.
- Use heatproof glass, stainless steel or heavy plastic. Never aluminium, which reacts violently with lye.
- Keep a bottle of white vinegar nearby for spills on skin or worktops, and rinse thoroughly with cool water afterwards.
Once the lye is fully mixed into the oils, it is neutralised as the soap saponifies, and the finished cured bar is perfectly safe to use.
Choose oils with a purpose in mind
Every oil brings something different to the bar. Olive oil is the backbone of most gentle recipes, giving a mild, creamy soap — though a bar of 100% olive oil can feel slimy until it has cured for six months or more. Coconut oil adds hardness, a big fluffy lather and deep cleansing, but above about 30% of the recipe it can leave skin feeling tight. Castor oil, in small amounts, boosts bubbles beautifully.
- Olive oil — 50–70% of the recipe for a mild, hard-wearing bar.
- Coconut oil — 20–30% for lather and longevity.
- Castor oil — 5–10% for a richer foam.
- Shea or cocoa butter — up to 10% for a creamier, more luxurious feel.
Natural colourants that survive the cure
Clays are the most reliable colourants for home soapmaking. They are cheap, easy to blend, add a little slip to the lather and hold their shade far better than most kitchen-cupboard powders. Kaolin gives a soft cream or white, French green clay a gentle sage, pink and rose clays a warm blush, and a spoonful of bentonite produces a pale grey-green. Activated charcoal makes a dramatic slate-black and is popular in facial bars.
Botanicals work too, but expect shifts. Dried nettle or parsley powder produces a soft green that darkens over the cure, turmeric gives a cheerful gold that can stain pale flannels, and cocoa powder makes a satisfying dark brown. Lavender buds scattered on top will turn brown within weeks — scatter them sparingly, purely for texture.
To use any of them, disperse one teaspoon to one tablespoon in about 15 ml of warm oil until smooth, then stir it in at light trace. For a swirled effect, split the batch between two jugs, colour one, and pour them together in alternating ribbons before giving a single slow stir.
A simple olive and coconut bar
This makes roughly 1.1 kg of soap, or about ten generous bars. Run the figures through a reputable soap calculator before you begin, so you can check the lye amount against your exact oils.
- 500 g olive oil
- 250 g coconut oil
- 100 g castor oil
- 119 g sodium hydroxide
- 280 g cold water, filtered if your tap water is very hard
- 1 tbsp kaolin clay, plus 1 tsp green clay for a swirl
Wearing your gloves and goggles, pour the lye into the water and stir until clear. Leave it to cool. Warm the oils gently until melted, then let them come down to around 40°C, with the lye solution within about 10°C of the oils. Pour the lye into the oils and blend in short bursts with a stick blender until you reach a light trace — the mixture should dribble off the blender in a visible trail. Stir in the clay, pour into a lined mould, and wrap it in a towel or pop it in a cardboard box with a blanket for 24 to 48 hours.
Curing, cutting and storing
Once the loaf is firm enough to handle, turn it out and cut it into bars with a sharp knife or a wire cutter. If it crumbles, it is still too soft — give it another day. Then the real waiting begins. Stand the bars on a rack with gaps between them, somewhere cool, dry and airy, and turn them once a week for four to six weeks. A spare bedroom or utility room is ideal; a damp shed or a steamy bathroom is not.
A fine white powder on top, called soda ash, is harmless — wipe it off with a damp cloth or simply leave it. If a bar zaps your tongue like a battery, it needs longer. Once it tastes of nothing but soap, it is ready. Store your cured bars in a cardboard box or paper bag in a dry cupboard, never sealed in plastic, and they will keep improving for a year or more.
