How to make Cold Process Soap

Cold Process Soap Making

The Lye Solution

Measure 340g cold water into a jug. Carefully add 125g sodium hydroxide beads, whisking constantly. Hold your breath initially to avoid the vapours, and stir until fully dissolved with no lumps.

The solution will rocket to nearly 95°C. Pop it in a bowl of cold water to cool (mind it doesn't float away).

The Oils

Gently melt 284g coconut oil and 170g palm oil in a small saucepan. Don't overdo it—turn off the heat whilst tiny solid bits remain and let them melt naturally.

Meanwhile, measure 454g olive oil (pomace grade works brilliantly) into your main soap-making pan. Add any optional antioxidant now.

Pour the melted coconut and palm oils into the olive oil and combine. Slowly pour in the cooled lye, whisking briskly. Watch as the mixture turns opaque and begins to thicken.

Reaching Trace

You've hit 'trace' when drizzled mixture leaves a visible trail on the surface before sinking back. This is your moment to add essential oils (20ml for this batch)—stir them in thoroughly.

Pour into your lined mould, cover with cardboard, and wrap in old towels. Leave at room temperature for up to 24 hours until solid.

Cutting & Curing

Once cool and firm enough to handle (give it 2-3 days if too soft), unmould and cut into bars. Cure for at least 3-4 weeks on absorbent paper with good air circulation. This makes harder, longer-lasting soap.

Tips

Fragrance: Stick with pure essential oils for your first attempts. Most fragrance oils contain alcohol that can cause 'seizing'—when your mixture sets solid before you can pour it. Disaster!

Colour: Food colourings rarely work. Try these instead:

• Ultramarines & oxides (max 1 tsp) mixed with water

• Turmeric for yellow, paprika for salmon tones

• Ground cinnamon mixed into a paste near trace

Add colour gradually—too much bleeds into the lather. Keep it subtle.

Dried botanicals: 

Most flower heads turn brown in the caustic mixture. Press dried lavender onto the surface after pouring instead (gloves on—it's still caustic!). Calendula petals are the exception.

Enrichments: 

Add 1 tbsp hempseed or wheatgerm oil at trace for extra nourishment. Same for honey. Exfoliants like oatmeal/poppyseeds. Use up to 60ml, ensuring the mixture's thick enough to suspend them.

Storage: Never store soap somewhere cold. Temperature changes cause 'sweating' that ruins the soap and any absorbent packaging. Room temperature is your friend.

Essential Terms

Saponification: The chemical magic where oils and lye create soap molecules. Each oil needs a specific amount of lye to transform.

Trace: When oils and lye have properly emulsified and thickened enough to leave trails on the surface.

Superfat: The safety net of extra oils (minimum 5%) that ensures no free lye remains in your finished soap.

Soda ash: That harmless white powder that sometimes appears on top when unsaponified lye meets air. Simply wash or wipe it off.