Castile soap originally refers to soap made exclusively from olive oil, named after the Castile region in Spain. Over time, the term has broadened to include soaps made with other vegetable oils, but traditional Castile soap remains a favorite for its gentle cleansing properties. Pure olive oil soaps are especially known for being moisturizing and kind to the skin, making them ideal for face and body use.

To make your own liquid Castile soap, you will need the following ingredients:

Olive Oil: 645 grams (approximately 22.7 ounces)
Potassium Hydroxide (KOH): 151 grams (approximately 5.3 ounces)
Distilled Water: 750 grams (approximately 26.5 ounces) for the lye solution, plus an additional 2500 grams (approximately 88 ounces) for dilution
Glycerin (optional): This can be added for extra moisturizing properties.

Tools Required

A large crockpot (6 quarts or larger)
An immersion blender
A reliable digital kitchen scale
Heavy-duty glass or stainless steel bowls
Safety gear: gloves, goggles, and a mask

Step 1: Prepare the Lye Solution

Measure the Ingredients: Carefully weigh out the potassium hydroxide and distilled water.
Mix the Lye: In a well-ventilated area, slowly add the potassium hydroxide to the distilled water (never the other way around). Stir until fully dissolved. The mixture will heat up and become cloudy, which is normal.

Step 2: Combine Oils and Lye

Heat the Olive Oil: Pour the olive oil into your crockpot and set it to a low heat.
Combine Lye and Oil: Once the lye solution has cooled slightly, slowly pour it into the warmed olive oil. Use your immersion blender to mix until the mixture reaches a thick trace (similar to a pudding texture).

Step 3: Cook the Soap Paste

Cover and Cook: Put the lid on the crockpot and cook the mixture on high for about 3 to 4 hours. Stir every 30 minutes to ensure even cooking.
Check for Clarity: After cooking, check the soap paste by taking a small amount and mixing it with hot water. If the mixture becomes clear, it’s ready for dilution.

Step 4: Dilute the Soap Paste

Add Water: Gradually add the remaining distilled water (2500 grams) to the soap paste in the crockpot. Break up the paste as you add water.
Dissolve: Set the crockpot to a low heat and allow the mixture to dissolve fully, which may take several hours. Stir occasionally to help the process along.

Step 5: Final Adjustments

Test the pH: Once fully dissolved, test the pH of your soap. It should be between 9 and 6. If it’s too high, you can adjust it with a citric acid solution.
Bottle Your Soap: Once the soap is at the desired pH, pour it into clean, dry bottles for storage.

Use Distilled Water: This helps prevent cloudiness in your soap and ensures a longer shelf life.
Safety First: Always wear gloves and goggles when working with lye, as it can be hazardous.
Customize Your Soap: You can add essential oils or natural colorants after dilution for fragrance and aesthetic appeal.

Making your own liquid Castile soap with olive oil is a rewarding process that yields a gentle, effective cleanser suitable for various uses. With just a few ingredients and some patience, you can create a high-quality soap that is both economical and kind to your skin. Enjoy the satisfaction of crafting your own natural soap and the benefits it brings to your daily routine!

For more detailed guidance, you can refer to resources like Elly's Everyday and Oh, The Things We’ll Make for additional tips and variations. Happy soap making!