Homemade Liquid Castile Soap Tutorial

Things You'll Need

  • Rubber gloves
  • Face mask
  • Safety goggles
  • Distilled water
  • Mixing bowl
  • Measuring scale
  • Lye crystals, or sodium hydroxide
  • Spatula
  • Stainless steel pot
  • Pomace-grade extra virgin olive oil
  • Kitchen thermometer
  • Electric hand mixer
  • Soap mold
  • Wax paper
  • Cardboard
  • Towel
  • Kitchen knife
  • Vegetable grater
  • Funnel
  • Soap dispenser bottle
Vitamin E-rich olive oil naturally moisturizes the skin.
Vitamin E-rich olive oil naturally moisturizes the skin. (Image: Kesu01/iStock/Getty Images)

Castile soap finds its origins in Castile, Spain, where it was made of olive oil and animal fat. Today's castile soap retains these natural roots, relying only on plant oils and an alkali ingredient -- sodium hydroxide or potassium hydroxide -- to create a gentle, biodegradable and eco-friendly soap. Commercially produced castile soap, however, tends to come at a higher price than other off-the-shelf options. Make your own castile soap bars, then break them down into liquid form for convenient hand-washing.

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Make the Bars

Step 1

Put on rubber gloves, safety goggles and a face mask.

Step 2

Pour 10 ounces of distilled water into a mixing bowl. Measure out 4.33 ounces of lye crystals and gently stir them into the water with a spatula until they dissolve completely. Wait as the water becomes hot, then set the mixture aside and allow it to cool.

Step 3

Heat 34 ounces of Pomace-grade, extra-virgin olive oil in a stainless steel pot over low to medium heat. Use a thermometer to keep track of the oil's temperature; when the temperature reaches 100 degrees Fahrenheit, cut the heat. As the oil heats, check the temperature of the water-lye mixture; it should cool down to about 100 degrees as well.

Step 4

When both the oil and water-lye solution reach 100 degrees, drizzle the lye solution into the oil and stir it with an electric hand mixer. Mix until it takes on a gooey texture, known as the trace stage.

Step 5

Line a soap mold with wax paper, then slowly and evenly pour the soap mixture into the mold. Place a piece of cardboard over the trays and a towel on top of the cardboard, then allow the soap to rest for 48 hours.

Step 6

Remove the hardened soap from the mold and carefully cut it into bars with a sharp kitchen knife. Place the soap on a sheet of wax paper and allow it to cure for at least two weeks. After two weeks, the soap is ready to use or liquefy.

Liquefy the Soap

Step 1

Cut one average-sized bar of the homemade castile soap into smaller, more manageable chunks. Using a vegetable grater, grate the soap into a pot of boiling water. Use about 8 cups of distilled or filtered water per bar.

Step 2

Allow the soap flakes to completely dissolve in the boiling water, stirring if necessary. Let the water and flakes cool; the mixture will take on the consistency of a concentrated liquid soap.

Step 3

Funnel the liquefied castile soap into a soap dispenser bottle. If the soap hardens, heat the bottle under hot running water or lightly boil it to liquefy the soap once again.


  • To speed up the cooling process for the water and lye mixture, place your mixing bowl in a sink full of ice water.

    To add a scent to your castile soap, mix in about 10 drops of the essential oil of your choice when you stir the water-lye mixture into the olive oil.

    Use liquid castile soap as a gentle shampoo.


  • The face mask and goggles protect you from breathing in the fumes that occur when you mix lye with water. For optimal safety, hold your breath as you stir. The fumes will fade in about 10 seconds.


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