How to Make Castile Soap: Cold Process Olive Oil Soap Tutorial


Olive oil soap is pure and simple to make. You can adjust the lye amounts and use this base recipe as cleaning soap or something for your hands and body.

🌟 If you are a beginner soapmaker, please read this soapmaking overview and watch the video before proceeding 🌟

homemade soap on tray lined with towel

How to make cold process Castile soap

Are you looking for a new soap recipe?

This is a simple and pure Castile soap recipe. It’s easy to make, requires only three ingredients, and is gentle on your skin. You can use it as hand or body soap or even cleaning soap!

The base of this recipe is olive oil, which has been used for centuries in soaps because of its moisturizing properties. Olive oil also makes the bar harder and longer-lasting than most other oils. And with just three ingredients, there are no complicated steps involved in making this cold process Castile soap!

Why you’ll love this recipe

  • It requires just three ingredients. 
  • The base of this recipe is olive oil, which has been used for centuries in soaps because of its moisturizing properties.
  • Simple to make with no complicated steps involved

What you’ll need

olive oil, soap, and sodium lactate on white concrete surface


  • Soap ingredients must be measured by weight. A scale is essential.
  • Cold process soapmaking involves lye which is dangerous if handled improperly. Make sure you work in a well-ventilated area and always use goggles and gloves.
  • Have all of your supplies out, measured, and ready before you begin. Being stressed or hurried is a recipe for disaster.

Step by step olive oil soap

Combine the lye and water in separate, non-reactive containers. Carefully add the lye to the water (NOT the other way around! Remember the saying “snow floats on the lake.”). Place the lye water in a safe, well-ventilated place to cool.

lye and water being measured over digital scale, then mixed in pyrex container

Then measure out all of that beautiful olive oil into a large saucepan on top of medium heat until it reaches 130 – 140 degrees Fahrenheit.

olive oil bottle being poured into stainless steel pot

Add the lye and oil together in a mixing container. (Prepare your soap mold and have any fragrance and color ready to go before combining.) If you’re using sodium lactate, add it to the cooled lye water. Combine the lye water with the oil in a pot with a stick blender until “trace” is reached.

lye water poured into oil, blending until batter forms

Pour the soap into the mold. Pour straight into the soap mold as soon as possible. Allow to cure in the mold for 24-48 hours at room temperature before unmolding and cutting into pieces. It will seem very soft at first, but over the next day will become very hard.

greenish yellow soap batter and fulled cured loaf of white soap

Unmold and cut into bars carefully.

cutting large loaf of castile soa into bars
this bar cured a bit too long and is hard to cut!

Curing and storing the soap

More than any other type of soap, Castile soap benefits from a long cure time.

Curing time depends on the size of the bars and how humid or dry the area is, but as a general rule, wait at least four weeks.

Tips for success

  • This soap acts quite differently from most recipes: it is very soft at first but cures to be very hard. This can make it difficult to gauge when to cut it into bars.
  • This recipe really does best when poured into individual molds. You don’t need to worry about the soap getting too hard to cut.
  • Sodium lactate is very helpful
  • This recipe has no natural color, the soap hardens to a pure white. To get a yellow-green color, you’ll need to add it.

FAQs about olive oil soap

Can you use other oils in this recipe?

No, it won’t be a castile soap unless it is 100% olive oil. There is a type of soap known as Bastille Soap which is mostly olive oil and adds one other oil.

What is the trace stage of soap making?

You’ll see the soap mixture thicken and form a batter. When you lift your stick blender, there will be a trail of soap resting on top rather than just sinking in.

How should I store the soap?

Just like any other handmade soap, you’ll want to keep your Castile soaps in a cool dark place. Let them breathe as they are curing.

Why is it called Castile Soap?

Olive oil soap originated in the Castile region of modern-day Spain, where olive oil is produced. It was famous for being a high-quality soap during the middle ages and Renaissance.

More cold process recipes you’ll love

Recipe for Castile soap

7 bars of white homemade soap on olive patterned dish towel

Olive Oil Castile Soap Recipe

A pure and simple olive oil soap recipe. Easy to make.


  • 9.5 ounces water
  • 3.82 ounces lye
  • 30 ounces olive oil
  • 2 tablespoons orange essential oil
  • 0.6 ounces sodium lactate optional, creates a firmer bar


  • Combine the lye and water. In separate, non-reactive containers, measure out the lye and water. Add the lye to the water, stirring until the lye dissolves. Set aside in a safe, well-ventilated place and allow the lye water to cool to 100-115 degrees while you warm the olive oil.
  • Warm the olive oil. Add all the olive oil to a large, non-reactive saucepan and melt over medium-low heat until 130-140 degrees. Set aside to cool to 100-115 degrees. This may take an additional hour or so.
  • Combine lye solution with the oil. (Before blending, prepare your soap mold and have any fragrance and color ready to go.) If using the sodium lactate, add it to the cooled lye water. Pour the lye water into the pot with the oil and combine with a stick blender until “trace” is reached. The batter has traced when a trail rests on the surface of the liquid rather than immediately sinking back it. This will take at least five minutes of blending.
  • Pour soap into mold. Immediately pour into the soap mold. Allow the soap to cure in the mold for 24-48 hours at room temperature
  • Unmold and cut into bars. Carefully turn the soap out of the mold. Cut into bars. Place on breathable fabric or wire racks and allow the soap to finish curing at room temperature in a well-ventilated space for at least four weeks. A longer cure time will result in harder, longer-lasting bars.


Working with lye requires safety precautions: be sure to wear goggles, gloves, and long sleeves.  Take care not to splash or spill the lye water or the raw soap batter, as both are caustic.  Take special precautions if you have young children or pets.
Lye is calculated at 6% superfat.  
For a cleaning soap, use 3.98 ounces of lye, which is 2% superfat.

Castile soap is a simple, pure soap to make that only requires three ingredients. This cold process Castile soap recipe is easy to follow and doesn’t have any complicated steps involved. You can use this soap as hand or body soap, or even cleaning soap.

How to Make Castile Soap: Cold Process Olive Oil Soap Tutorial

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Recipe Rating


  1. 5 stars
    I love the simplicity of this recipe. Thank you for sharing it. I have been infusing different herbs into olive oil so I’m so very excited to experiment with them.