Step-by-Step Liquid Castile Soapmaking

Now that we have our tools, safety precautions, and ingredients ready, it’s time to make liquid Castile soap! This process involves saponification, cooking the soap paste, diluting it, and adjusting the final consistency. Follow these steps carefully to create a smooth, high-quality liquid soap.

 

Step 1: Preparing Your Work Area

Before you start, set up your workspace to ensure a smooth and safe soap-making experience.

✅ What to Do:

✔️ Gather all tools and ingredients ahead of time.
✔️ Wear safety gear – gloves, goggles, and long sleeves to protect against lye burns.
✔️ Work in a well-ventilated area to avoid inhaling fumes when mixing the lye solution.
✔️ Use dedicated soap-making equipment (no food use afterward).

💡 Pro Tip: Cover your work area with newspaper or a silicone mat to make cleanup easier.

 

Step 2: Making the Lye Solution

Potassium hydroxide (KOH) must be dissolved in distilled water before mixing with oils. This step creates heat and fumes, so handle it carefully.

✅ How to Make the Lye Solution:

1️⃣ Measure out the correct amount of distilled water in a heat-resistant container.
2️⃣ Slowly add the potassium hydroxide (KOH) into the water, stirring constantly.

⚠️ NEVER add water to lye! This can cause a violent reaction.

3️⃣ Stir until the lye is fully dissolved. The mixture will heat up quickly.

4️⃣ Allow the lye solution to cool to 120-140°F (49-60°C) before mixing with oils.

💡 Pro Tip: Mix lye outdoors or under a kitchen vent hood to minimize exposure to fumes.

 

Step 3: Heating the Olive Oil

✅ How to Heat the Oil:

1️⃣ Pour olive oil into your crockpot (slow cooker).
2️⃣ Turn the heat to LOW and allow the oil to reach 120-140°F (49-60°C).
3️⃣ Use a thermometer to check the temperature.

💡 Pro Tip: Keep the lye solution and oils at similar temperatures before mixing to ensure smooth blending.

 

Step 4: Mixing the Oils and Lye

Now it’s time to combine the lye solution and olive oil to start the soap-making process.

✅ How to Mix:

1️⃣ Slowly pour the cooled lye solution into the warmed olive oil.
2️⃣ Use a stick blender to blend the mixture in short bursts.
3️⃣ Continue blending until the soap reaches “trace”—this means the mixture thickens to a pudding-like texture.

💡 Pro Tip: Avoid over-blending! Stop blending when the soap reaches light to medium trace—too much blending can make it too thick.

 

Step 5: Cooking the Soap Paste

At this stage, the soap is not yet ready to use—it must be cooked to complete the saponification process.

✅ How to Cook the Soap Paste:

1️⃣ Set the crockpot to LOW heat and cover with a lid.
2️⃣ Stir occasionally with a long-handled spoon to prevent scorching.
3️⃣ Over the next 3-4 hours, the soap will change textures: Grainy and thick → Dry and clumpy → Glossy and translucent

4️⃣ When the soap becomes shiny, gelatinous, and clear, it is fully saponified and ready for dilution.

💡 Pro Tip: Test for doneness by dissolving a small amount in warm water—if it turns milky, keep cooking; if it remains clear, it’s ready!

 

Step 6: Diluting the Soap Paste

To transform the thick soap paste into liquid Castile soap, it needs to be diluted with warm distilled water.

✅ How to Dilute the Soap Paste:

1️⃣ In a separate pot, heat 30 oz of distilled water until warm (but not boiling).
2️⃣ Slowly add the warm water to the soap paste, stirring gently to help it dissolve.
3️⃣ Cover and let it sit overnight—this allows the paste to fully dissolve into a smooth liquid soap.

💡 Pro Tip: If your soap isn’t fully dissolved by morning, gently warm it and stir again.

 

Step 7: Adjusting & Bottling

Once the soap is fully dissolved, it’s time to adjust the consistency and add optional ingredients.

✅ Adjusting the Thickness:

    • If too thick: Add more warm distilled water, a little at a time, until it reaches the desired consistency.

    • If too thin: Use a natural thickener like:
        • Salt – Dissolve ½ teaspoon in warm water and mix into soap.

        • Guar gum or xanthan gum – Blend ¼ teaspoon into the soap for a silkier texture.

✅ Adding Essential Oils (Optional):

    • Once the soap has cooled to room temperature, add essential oils for fragrance.

    • Stir well to evenly distribute the scent.

✅ Bottling & Storage:

1️⃣ Pour the finished soap into bottles or dispensers.
2️⃣ Store in a cool, dry place—liquid Castile soap can last 6-12 months.

💡 Pro Tip: Shake the bottle before each use to keep the soap well-mixed.

 

Key Takeaways from This Lesson

✅ Preparing your workspace and wearing safety gear is crucial before handling lye.
✅ Slowly mix potassium hydroxide (KOH) into water—never the other way around.
✅ Using a stick blender helps reach “trace,” which is the thickening stage before cooking.
✅ The soap paste must be cooked for 3-4 hours until it becomes glossy and translucent.
✅ Diluting the paste with warm distilled water turns it into a pourable liquid soap.
✅ Adjusting thickness and adding essential oils helps customize the final product.

Next Lesson: Testing & Using Your Liquid Castile Soap

Now that your soap is bottled and ready, let’s cover how to test the pH level, troubleshoot common issues, and explore different ways to use liquid Castile soap!

🔹 How to test pH for safe usage
🔹 Common soap-making mistakes & fixes
🔹 Creative uses for liquid Castile soap

➡️ See you in the next lesson! 🎉