How do I make clean layers in soap?
Short answer
Blend only to 'just emulsified', divide straight away, finish each layer separately, and keep the soap cool so it doesn't gel.
Explanation
Gel heat softens the layers so they bleed into each other, so layered bars are made no-gel. Blend the main batch only until just emulsified, then divide it into one container per layer immediately. Otherwise the last portion will be too thick to pour. Bring each portion to medium trace, add its colorant, oil and fragrance, and pour slowly over the back of a spoon held just above the previous layer. Tap after each pour and texture only the top.
What to do
- Soap at a cool 30–35 °C.
- Don't insulate; leave the mold somewhere cool or in the fridge for 12–24 hours.
- Expect to unmold after 3–5 days and cure 8–10 weeks.
Source: The Big Book of Homemade Soap — Four Spices Layered Exfoliating Bar: Precision Layering & Natural Texture