Castile soap is a cold process soap made with 100% olive oil. The name “Castile” refers to the Castile region of Spain, which is where this type of soap is thought to have originated. Olive oil is a popular choice for soap making that works well in combination with many other oils. It’s a fantastic option for making soap for sensitive or dry skin. It makes a gentle bar with a rich, creamy lather and adds moisturizing properties to the soap. Olive oil is also one of the very few oils that can be used successfully at 100% in a recipe.
Castile soap is an excellent product that many people love but it does require a few special considerations. Because olive oil is liquid at room temperature, the mixture takes longer to come to trace. This means increased mixing time before it can be poured into molds. It also means that most fragrances and colorants can be blended in, rather than stirred since there is less worry about acceleration. Castile soap also takes longer to harden in a mold than recipes that contain hard oils. Castile soap can sometimes require up to two weeks before it can be removed from the mold. But don’t worry, there are a few things you can do to shorten that timeframe.
A water discount helps soap harden much faster. Water discounting means using less water than you normally would in a recipe. This means the lye solution is more concentrated, making the soap thicken more quickly. It also means the bar will harden in the mold faster, as there is less water that needs to evaporate. We’ll be using a 20% water discount in this recipe to help speed things up.
Ensuring that your soap goes through the gel phase is another way to get a harder bar and a shorter time in the mold. The gel phase is the part of the saponification process where the soap heats up and temporarily turns gelatinous. Heat speeds up the saponification process, hardening the soap faster. Check out our blog on the gel phase to learn more.
Combining a 20% discount with the forced gel stage should enable this soap to be removed from the mold in four to five days. The bars will still be softer than your average cold process soap. Castile soap benefits from a longer cure which gives the bars time to further harden. The soap will be safe to use after the standard four to six-week cure time, but many soap makers prefer to let castile soap cure anywhere from a few months to a full year!
Using 100% olive oil results in a beautifully simple cream-colored bar. To accentuate that simplicity, we’ve opted to not use any colorants and to add only a classic lavender scent.
- 35 ounces pure olive oil
- 4.5 ounces sodium hydroxide lye
- 9.2 ounces distilled water
- 2 ounces Lavender Essential Oil
- 10-inch silicone loaf mold
- Immersion blender
- Digital kitchen scale
- Small bowl for essential oils
- Glass bowl for lye mixture
- Large glass or stainless steel bowl for oils
- Pot or double boiler
- Spoon or rubber spatula
- Safety glasses or goggles
- Measure 2 ounces of lavender essential into a small glass bowl and set aside.
- Weigh out the lye and water into two separate bowls. Slowly pour the lye into the water and gently stir until the lye has fully dissolved and the liquid is clear. Set aside to cool.
- Pour the olive oil into your mixing bowl and place it on top of a pot that’s about 1/3 full of water. (This is where a double boiler could also be used.) Bring the water to a boil and heat the oil to around 120° to 130°F.
- When the lye water and the oil have both reached 120° to 130°F and are within 10 degrees of each other, carefully add the lye water to the oil.
- Blend until you reach a light trace. This part will require patience as the olive oil is slow to thicken.
- Add the lavender essential oil and blend. Pulse the immersion blender and use it to stir until there are no longer streaks of essential oil in the mixture. Don’t worry about over blending. Continue to blend until you reach a thin medium trace.
- Pour the soap mixture into the mold, using a spoon or spatula to scrape the bowl. Gently tap the mold on your work surface to help get rid of any air bubbles.
- Cover the mold with a lid or piece of cardboard and insulate with a towel or blanket for up to 24 hours to help promote the gel phase. After 24 hours, remove the insulation and continue letting the soap harden in the mold for an additional 3 to 4 days.
- Carefully remove the soap from the mold, cut it into bars, and set aside to cure. Check bar hardness after 4 to 6 weeks. At this point, you may start to use the soap or continue letting it cure for up to 12 months until desired firmness is achieved.