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Castile vegetable soap is a natural, organic soap made from olive oil, water, and lye. Its origins trace back to Aleppo, and it was later introduced to the Castile region of Spain during the Crusades, where it gained significant popularity. Over the centuries, this gentle soap has been used for various purposes, including bathing, shampooing, laundry, and floor cleaning. Once you’ve crafted your Castile soap bars, you can use them in solid form or mix them with water to create liquid soap. Refer to Step 1 and the steps below to learn more about making Castile soap.
Steps
Preparing the Materials for Making Soap
Gather your tools. Set up a workspace in your kitchen or near a water source, and lay out your tools to begin. Bowls, measuring tools, and utensils should be dedicated solely to soap-making – do not use them for food preparation, as soap residue can stick to them. You’ll need the following tools to make Castile soap:
- Large measuring cup
- Stainless steel pot
- Large mixing bowl
- Mixing spoon
- Hand blender or mixer
- Meat thermometer
- Kitchen scale
- Rubber gloves and safety goggles (for handling lye)
- Pure lye (stored in a plastic container, which can be kept away when not in use; you’ll need 120 g of lye to make approximately 10 soap bars)
Prepare the oils. Pure Castile soap is made entirely from olive oil, but many soap makers use a blend of oils to create a more balanced soap. Pure olive oil soap doesn’t produce a rich lather, which can leave the bars feeling slightly slimy on the surface. Coconut oil is often added to enhance lathering, while palm oil helps harden the soap. A ratio of 8 parts olive oil, 1 part coconut oil, and 1 part palm oil yields an excellent soap. After measuring the oils according to this recipe, you’ll have 1010 ml of oil:
- 810 ml olive oil
- 100 ml coconut oil
- 100 ml palm oil
Add essential oils if desired. If you want to scent your soap, add 10 drops of your preferred essential oil. Increase the amount for a stronger fragrance or reduce it to 5–7 drops for a subtler scent. Popular essential oils for Castile soap include:
- Peppermint
- Orange, lemon, or grapefruit
- Lavender
- Rose
- Patchouli
- Pine
- Sandalwood
- Bergamot
Prepare the molds. The molds you use will determine the size and shape of your finished soap bars. If you want rectangular bars, choose a rectangular mold like a bread loaf pan; the soap will resemble a loaf of bread, which you can then cut into smaller bars of your desired thickness. Line the molds with wax paper for easy removal.
- Molds are available at craft stores and soap-making supply shops, or you can search online for more options.
- If you prefer not to buy molds, you can repurpose an old shoebox into a soap mold. Simply find a sturdy shoebox, tape the corners to seal the edges, and line it with wax paper.
- You can also craft your own wooden molds or use a wooden box as a soap mold. Ensure the mold is wide and deep enough to create bars of your desired size.
Mixing Lye and Oils
Wear protective gear. Lye is a corrosive substance that can burn your skin and eyes and harm your lungs if inhaled. If this is your first time handling lye, take extra care to ensure you work safely. Put on rubber gloves and safety goggles before opening the lye container. Open a window and turn on a fan to ensure proper ventilation.
- Keep a bottle of white vinegar nearby. If you spill any lye, the vinegar will neutralize it.
- If you accidentally touch or inhale too much lye, contact your local poison control center immediately. You can find the number online. In the U.S., call Poison Control at 1-800-222-1222.
Prepare the lye solution. When mixing lye with water, precision is crucial. For this recipe, you’ll need 300 ml of water and 120 g of lye. Use separate containers and measure the quantities accurately using a scale. Carefully add the lye to the water. The mixture will immediately heat up and turn cloudy, then clear as it cools. It takes a few minutes for the solution to cool. Use a meat thermometer to check the temperature. The lye solution is ready to use when it reaches 38°C.
- Never pour water into lye – always add lye to water. Pouring water into lye can cause an explosive reaction.
- When measuring ingredients, ensure you zero out the scale after weighing the first container to avoid affecting subsequent measurements.
- If you want to make a larger or smaller batch of soap, use a lye calculator to determine the exact amounts of water and lye needed.
Heat the oil mixture. Heat the oil mixture while waiting for the lye to cool. Pour the oil blend into a pot and heat it over medium-high heat. Stir the oils to ensure they blend smoothly. Continue heating until the mixture reaches 38°C. Use a meat thermometer to determine when the oil mixture is ready to combine with the lye. The oils and lye solution should be at nearly the same temperature to mix properly.
- Neglecting to match the temperatures of the oils and lye can result in improperly formed soap. Always use a meat thermometer to check both mixtures and complete this critical step.
Mix the lye and oil mixture. Pour the lye solution into the oil mixture. Use a hand blender or mixer to combine everything thoroughly. After a few minutes, the mixture will begin to thicken. When you lift the blender and see trails left behind, the mixture has reached "trace." It should have a consistency similar to honey.
- You can use a spoon to mix the lye and oils, but it will take longer for the mixture to reach trace.
Add essential oils. Once the mixture has reached trace, you can add essential oils to scent the soap. Add 10 drops of essential oil and mix thoroughly until fully incorporated.
Pouring into Molds and Curing the Soap
Pour the soap into the prepared molds. Be careful not to spill the soap while pouring it directly into the molds. Cover the molds with a clean cloth or towel, ensuring the cloth doesn’t touch the soap but wraps around the edges of the molds. Let it sit undisturbed for 48 hours.
- During the first 48 hours, the soap will set and harden. However, it’s not yet ready for use; it needs to cure to allow water to evaporate and become milder. Avoid using the soap immediately, as it may still be harsh on your skin.
- After 48 hours, check the soap’s surface. If there’s a film or it crumbles easily, the soap is unusable. Excess lye can harm your skin, or the lye and oil mixture may not have fully combined. Unfortunately, there’s no way to salvage the batch if this happens – you’ll need to discard it and start over.
Remove the soap from the molds. Store-bought soap molds often have removable sides, making it easy to release the soap. If using a shoebox, gently tap or cut away the sides. For regular molds, simply tap them to release the soap.
Cut the soap into bars. Decide on the thickness of your soap bars: 3 cm is standard, but you can make them thinner or thicker as desired. Use a ruler to measure the thickness and mark evenly spaced lines to guide your cuts. To cut the soap, you can use:
- A sharp knife. Avoid serrated knives if you don’t want wavy edges on your bars.
- A dough cutter. This common baking tool is also excellent for cutting soap.
- A cheese wire. Keep the wire taut for clean, straight cuts.
Arrange the soap bars to cure. Place the bars on a baking sheet or tray lined with wax paper. Store them in a cool, dry place for at least 2 weeks and up to 9 months. The longer the soap cures, the better it becomes; it will lather more and have a smoother texture.
- You can start using the soap after a few weeks. It’s ready when it’s firm and has no chemical smell.
Making Liquid Castile Soap
Grate 110 grams of solid Castile soap. This amount is equivalent to one medium-sized bar of soap. Use a cheese grater or a knife to shred the soap into small pieces. This step helps the soap dissolve faster in hot water.
Measure 8 cups of water to boil. Pour the water into a pot and set the stove to high heat. Bring the water to a full boil.
Combine the water and grated soap. Pour the water into a large bowl or plastic container, then stir in the grated soap. Let the mixture sit for a few hours until it thickens slightly. If the soap becomes too thick, you may need to reheat it and add more water. It should reach a consistency similar to shampoo at room temperature.
Transfer to a bottle. Store the liquid soap in a plastic bottle and keep it in the bathroom or kitchen. The liquid soap will remain usable for several months at room temperature. It can be used for shampooing, cleaning skin, laundry, dishes, or other household items.
Tips
- Consider adding supplementary oils such as lavender essential oil, eucalyptus essential oil, or orange essential oil to enhance the soap's fragrance and add color.
- Experiment with adjusting the ratios of the base ingredients to alter the soap's texture, concentration, and scent. It’s a good idea to start by reducing the amount of lye and gradually adjust rather than adding too much lye at once.
- Using a hand blender can make the process of mixing the lye solution into the oils easier and faster. Ensuring the lye and oils are fully emulsified is crucial, so remember to stir vigorously.
Warning
- Exercise extreme caution when handling lye and adding it to water. Wearing plastic gloves and working in a well-ventilated area are effective ways to avoid lye burns and harmful fumes.
- Castile soap doesn’t produce much lather, but it cleans just as effectively as lathering soaps.
What You Need
Tools
- Large measuring cup
- Stainless steel pot
- Large plastic or glass bowl
- Rubber spatula
- Hand blender or mixer
- Meat thermometer
- Kitchen scale
- Plastic gloves and safety goggles (for handling lye)
- Tray
- Wax paper
- Soap molds
Ingredients
- Pure lye (stored in a plastic bottle, which can be kept away when not in use; you’ll need 130ml to make 10 medium-sized soap bars)
- Olive oil
- Palm oil
- Coconut oil
- Essential oils
- Water
