Want to craft pure, gentle Castile soap at home? As a seasoned soap maker, this is one of my go-to recipes—simple, effective, and ideal for beginners.
This all-natural soap is mild on the skin and far easier to make than you might think.
Traditional 100% olive oil Castile can be soft and slow to set, often taking hours to trace. Drawing from my experience, I've refined this formula with complementary oils for a firmer bar that retains olive oil's renowned gentleness.
Contents 
- 570 ml of olive oil
- 75 ml coconut oil
- 75 ml palm oil with sustainable certification
- 230 ml of cold water
- 90 g of caustic soda
- 5 to 10 drops of essential oil (e.g., peppermint, lemon, or lavender)
- A large stainless steel tray
- A suitable mold (silicone cake mold)
- A measuring cup with glass spout
- A silicone spatula
- 2 cooking food thermometers
- An apron
- Long rubber gloves
- Safety glasses
- An immersion blender
- A digital scale
- A large steel (or stainless enamel) saucepan
1. Gather and precisely measure all ingredients using your digital scale. Accuracy is crucial for proper saponification.
Warning: Deviating from these ratios can compromise the process.
2. Don your safety gear: glasses, mask, apron, and long rubber gloves.
3. Pour the cold water into the tall glass measuring cup with spout.
4. Slowly add the caustic soda to the water.
5. Stir gently with the silicone spatula until fully dissolved. The mixture will heat up from the reaction—let it cool.
6. In the large saucepan, gently melt the olive, coconut, and palm oils (essential oils later).
7. Insert a thermometer into the lye solution and another into the oils.
8. Monitor until both reach exactly 43°C.
9. Slowly pour the lye solution into the oils.
10. Add your chosen essential oils.
11. Blend with the immersion blender: start slow without powering on, then use 3-second bursts. Stir manually between bursts until it reaches 'trace'—a thick, pudding-like consistency where saponification begins.
12. Pour into the mold and smooth the top.
13. Cover with cardboard, wrap in a towel to insulate, and let sit 24 hours.
14. Unmold the hardened soap and air-dry the block for 1-2 days.
15. Cut into bars (wear gloves—still caustic).
16. Place bars on a cloth-covered tray, spaced apart for airflow.
17. Cure in a dry spot, turning daily for the first week, then every other day for 3-4 weeks.
You've done it—six bars of luxurious homemade Castile soap! Gentle, pure, and ready after curing. Test on your hands first.
Caustic soda demands respect—I've handled it countless times safely with these proven steps.
Always wear eye protection and gloves. If it contacts skin, neutralize with vinegar, then rinse with water.
Avoid lye fumes during mixing (a scarf works for me, or use a mask). Remember: always add lye to liquid, never liquid to lye, to prevent splashes.
For cleanup, let residues harden, scrape into a bag, and use vinegar in soapy water while gloved.
