Ingredients & Soap Formulation
Now that we have covered safety precautions and essential tools, it’s time to dive into the basic ingredients needed to make a 1-pound batch of liquid Castile soap. This recipe uses simple, natural ingredients to create a gentle, moisturizing, and multipurpose soap.
Basic Ingredients for Liquid Castile Soap (1 lb Batch)
| Ingredient | Weight | Purpose in Soap Making |
| Olive Oil | 500g | Primary oil that creates a mild, moisturizing soap with a creamy lather. |
| Vegetable Glycerin | 271g | Helps retain moisture, increases transparency, and acts as a natural humectant. |
| Potassium Hydroxide (KOH – Lye) | 116g | The alkaline substance that reacts with the oils to create soap (saponification). |
Why These Ingredients?
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- Olive oil is the traditional base for Castile soap, providing moisturizing and gentle cleansing properties.
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- Vegetable glycerin adds a natural hydrating effect, making the soap softer and more conditioning.
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- Potassium hydroxide (KOH) is used instead of sodium hydroxide (NaOH) to create a liquid soap instead of a solid bar.
💡 Pro Tip: Use high-quality, extra virgin olive oil for a gentler, skin-friendly soap. Lower-grade olive oils (like pomace) can still work but may affect the final color and texture.
Optional Additives for Customization
One of the best parts about making your own liquid Castile soap is the ability to customize it with various additives. Here are some common options:
1. Essential Oils (for Scent & Skin Benefits)
Adding essential oils enhances your soap’s fragrance and provides additional aromatherapy benefits.
🌿 Lavender – Calming and soothing for the skin
🍋 Lemon – Uplifting and great for household cleaning
🌿 Tea Tree – Antibacterial and antifungal, ideal for acne-prone skin
🌱 Peppermint – Refreshing and cooling, perfect for morning showers
🌲 Eucalyptus – Invigorating and great for congestion relief
💡 Usage Tip: Add 5-10 drops of essential oil per 8 ounces of finished soap for a mild fragrance.
2. Herbal Extracts (for Added Skin Benefits)
🌿 Chamomile extract – Soothing and anti-inflammatory
🌿 Calendula extract – Healing and great for sensitive skin
🌿 Aloe vera gel – Hydrating and cooling
💡 How to Add: Mix 1-2 tablespoons of herbal extract per pound of soap after dilution.
3. Natural Thickeners (for a Richer Consistency)
While liquid Castile soap tends to be thinner than commercial soaps, you can thicken it naturally:
🧂 Salt (Sodium Chloride) – Helps thicken soap when added in small amounts.
🌿 Guar Gum or Xanthan Gum – Natural plant-based thickeners that improve texture.
💡 How to Add: Dissolve ½ teaspoon of salt per 8 ounces of diluted soap or ¼ teaspoon of guar gum per 8 ounces for a thicker consistency.
Key Takeaways from This Lesson
✅ Olive oil is the primary ingredient in traditional Castile soap, making it gentle and moisturizing.
✅ Vegetable glycerin enhances hydration and improves transparency.
✅ Potassium hydroxide (KOH) is used to create a liquid soap instead of a bar.
✅ Optional additives like essential oils, herbal extracts, and thickeners allow for customization.
✅ Salt, guar gum, or xanthan gum can be used to adjust the soap’s thickness.
Next Lesson: Step-by-Step Soap-Making Process
Now that we have our ingredients, let’s move on to the actual soap-making process!
🔹 Measuring and mixing ingredients
🔹 Saponification and cooking the soap paste
🔹 Diluting and storing liquid Castile soap