Lye Soap

2 minutes


Soap has been used since ancient times to clean skin, clothes and other materials. It is basically a mixture of oils, lye (caustic soda) and water blended together to combine into a soluble material that can remove oils when used with water and so is very useful.

Note Lye (caustic soda  sodium hydroxide) is strongly irritating and corrosive. It can cause severe burns and permanent damage to any tissue that it comes in contact with. Use with Caution and always wear protective clothing and equipment such as gloves and goggles. Do not use near children or pets. Work in a well-ventilated area.


  • 300g coconut oil
  • 700g olive oil
  • 142.3g Lye
  • 380g Water
  • 30g Essential oils for fragrance (if desired)
  • 2-3 tablespooons of dried flowers or coffee grinds if desired


  • Rubber gloves
  • Safety goggles
  • Stick blender
  • Weighing scales
  • Large, heat-safe bowl 
  • Measuring jug
  • Heat-safe bowl, ideally with a handle
  • Spatula to scrape bowl
  • Thermometer 
  • Soap Mould - eg milk carton with top cut off / plastic packaging / silicon mould
  • Teaspoon(if using fragrance) 
  • Sharp knife



  1. Carefully measure out your ingredients
  2. Put on your rubber gloves and safety goggles, and pour the sodium hydroxide into the bowl of water, being carful to avoid breathing any fumes
  3. Stir just long enough to make sure it all dissolves. Leave in a well ventilated area to cool to about 40 Celsius. This can take 30 – 90 mins.
  4. Melt your oils in the microwave or in a bowl over simmering hot water
  5. Allow to cool to between 30 – 40 Celsius
  6. Put your gloves and eye protection back on, and carefully pour the lye into the pot of oil
  7. Blending with your stick blender, and over the next 3 to 5 minutes you’ll see the mixture become thicker and more opaque.
  8. Lift the blender out and let some drips fall across the surface of the mixture, you should see them leave a visible pattern, ‘trace,’ before sinking back in. Keep blending and regularly checking until you have reached ‘trace’.
  9. Once the soap mixture has reached trace, stir in the fragrance oil, if using, until blended.
  10. You can add in other ingredients here such as dried lavender or dried coffee grinds to act as an exfoliator.
  11. Carefully pour the finished mixture into your soap mold
  12. Leave undisturbed in a well-ventilated area that's out of the way from children and pets for 24 hours. 
  13. After 24 hours is, de-mould your soap.
  14. Cut the loaf into bars with a sharp knife. 
  15. Leave the bars need to cure somewhere airy for 4 to 6 weeks
  16. Wash your hands! 


Clean up thoroughly. Wash all your equipment with dish soap and hot water while wearing your gloves. Never use soap making bowls and equipment for food or other domestic purposes. Store separately from other kitchen utensils.

Try making variations on this some with other oils or fragrances. Use an online lye calculator such as to find recipes and information.