How to Make Castile Soap

Castile Botanical Soap is a biological soap made from olive oil, water and alkali. It was invented in Aleppo, then brought to Castile in Spain during the Crusades, and became quite popular there. Over the centuries, people have used this mild soap in everything from bathing and washing hair to washing clothes and cleaning floors. After making Castile soap bars, you can use them in solid form or mix with water to make liquid soap. Refer to Step 1 and the steps below to learn more about how to make Castile soap.

Table of Contents

Prepare Soap Ingredients

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Preparing instruments. Prepare a spot in the kitchen or near a water source, and set aside the tools to get started. Bowls, measuring tools and utensils are intended for soap making only – do not use them to prepare food, as soap residue will stick. You will need the following tools to make Castile soap:

Large measuring cup
Stainless steel pot
Big bowl
Flour mixing spoon
Hand blender or mixer
Meat thermometer
Scales for use in the kitchen
Plastic gloves and goggles (for alkaline handling)
Pure alkaline (contained in a plastic bottle, which you can store when not in use; you will need 120 g of alkali to make an average of 10 bars of soap)

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Prepare the oils. Pure Castile soap is made from 100% olive oil, but many soapmakers use different oils to make a balanced soap. Pure olive oil soap does not create a fine lather, and this leaves the bar with only a little viscous on the surface. Coconut oil is often added to help create more lather, palm oil helps the soap to harden. A ratio of 8 parts olive oil, 1 part coconut oil and 1 part palm oil will make a good soap. After measuring the amount of oil as shown in this recipe. You will have 1010 ml of oil:

810 ml olive oil
100 ml of coconut oil
100 ml palm oil

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Add more oil if desired. If you want to scent your soap, you’ll need to add 10 drops of your favorite essential oil. Increase the amount of essential oil for a stronger scent, or reduce it to 5-7 drops for a milder scent. Common essential oils used to make Castile soap include:

Mint
Orange, lemon or grapefruit
Lavender
Rose
Vetiver grass
Pine
Guide
Bergamot

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Mold preparation. The mold you use will determine the size and shape of the finished bar of soap. If you want to make rectangular soap bars, choose a rectangular mold like a bread mold; The soap will look like bread, which you can cut into small pieces of arbitrary thickness. Line wax paper in the mold to easily separate the soap.

Molds are available at craft stores and soap makers, and you can search online for more options.
If you don’t want to go through the hassle of buying a mold, you can turn an old shoebox into a similar soap mold. Just find a sturdy shoe box, tape the corners to seal the edges, then line them with wax paper.
You can also make your own wooden molds, or use a wooden box to make soap molds. ^{[1] X Research Source} The mold needs to be wide and deep to create the desired bars of soap.

Mixing Alkali and Oil

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Wear protective gear. Alkaline is corrosive and can cause burns to the skin and eyes as well as damage to the lungs when inhaled. If this is your first time handling alkali, take great care to make sure you do it safely. Wear plastic gloves and safety goggles before opening the alkaline container. Open windows and turn on fans to make sure the room is well ventilated.

Place a bottle of white vinegar nearby. If you spill some alkali on the table, the vinegar will neutralize it.
If you accidentally touch or inhale too much alkali, call the nearest poison control center immediately, you can find a phone number online. In the US, call the Poison Handling Center at 1-800-222-1222.

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Make an alkaline solution. It is important when mixing alkaline with water to measure accurately. In this recipe you need 300 ml of water and 120 g of alkali. Using two separate containers, accurately measure the dose using the balance. Carefully add alkali to the water. The mixture will immediately start to heat and become cloudy, then clear again as it cools. Take a few minutes for the mixture to cool. Use a meat thermometer to check the temperature. Alkaline can be used when the temperature is 38°C.

Do not add water to alkaline – always add alkaline to water. Adding water to alkali will cause an explosive reaction .
When weighing ingredients, make sure you set the scale to zero after weighing the first jar, so as not to affect the next weighing.
If you want to make a larger or smaller batch of soap, use an alkalinity calculator ^{[2] X Research Source} to accurately measure the amount of water and alkali to use.

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Heat the oil mixture. Heat the oil mixture while waiting for the alkali to cool. Pour the oil mixture into the pan and heat over medium high heat. Stir in the oil so that they blend together. Continue heating until a temperature of 38°C is reached. Use a meat thermometer to determine when the oil mixture can be mixed with alkali. Oil and alkali need to be at roughly the same temperature to mix.

Not paying attention to the fact that the oil and alkali are at roughly the same temperature will cause the soap to form incorrectly. Remember to use a meat thermometer to measure the temperature of both mixtures and complete this important step.

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Mix alkali and oil mixture. Pour lye into the oil mixture. Use a hand blender or mixer to blend everything together. After a few minutes, the mixture will begin to thicken. When you take out the blender and see a streak, that’s when the mixture has “matched”. The mixture should have a consistency like honey.

You can use a spatula to mix the lye and oil, but it will take longer for the mixture to thicken.

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Add the essential oil. When the mixture has thickened, you can add essential oils to flavor the soap. Add 10 drops of essential oils and mix them with soap until the mixture is completely dissolved.

Molding and Soap Treatment

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Pour soap into the prepared mold. Be careful not to spill the soap when pouring it directly into the mold. Cover with a clean cloth or towel, do not let the cloth get into the soap, but wrap it around the edge of the mold. Let stand for 48 hours.

During the first 48 hours, the soap will form and harden. However, soap is still unusable; they must be left to dry for the water to evaporate and become softer. Do not use soap immediately, as it is still rough on your skin.
Check the soap surface after 48 hours. If there is a film on the face, or it comes off, the soap cannot be used. If the soap has too much alkali, it will cause skin damage when used, or the alkaline and oil mixture has not completely dissolved. Unfortunately, there’s no way to save this if this happens – you’ll have to throw out your batch of soap and start over.

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Remove the soap from the mold. Store-bought soap molds will have removable sides that allow you to easily separate the sides of the soap block from the mold. If using a shoebox, you can pat or cut off the side. If you use a regular mold you just need to pat them to fall off.

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Cut the soap into cakes. Decide on the thickness of the soap: 3 cm is the norm, but you can make the soap thinner or thicker if you want. Use a bar gauge, and make equally spaced lines to determine where to cut the soap. To cut soap, you can choose the following ways:

Use a sharp knife. Do not use a serrated knife, if you do not want the soap bar to have a wavy appearance.
Dough cutter. This is a fairly common baking tool used to cut dough, and is also very useful in cutting soap.
Cheese wire. Remember to keep the wire flat to create a neat, straight cut.

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Arrange the bars of soap to dry. Line up a baking tray or tray lined with wax paper and place the soap on it. Place them in a cool, dry place for at least 2 weeks, and up to 9 months. The longer you leave it on, the better the soap; it will produce more foam and have a better texture. ^{[3] X Research Sources}

You can start using soap after a few weeks. Soap can be used when it is hard and does not have a chemical smell.

Making Liquid Castile Soap

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Grate 110 g solid Castile soap. This amount is equivalent to an average size bar of soap. Use a cheese grater or knife to scrape the soap into small pieces. This step helps the soap to dissolve into the hot water faster.

Advice

Try adding some additional oils like lavender, eucalyptus, or orange essential oil to give the soap a fragrance and color.
Try varying the ratios of the base ingredients to change the texture, concentration, and scent of the soap. It would be a good idea to start off by reducing the alkalinity and continue doing so rather than increasing the alkalinity too much.
A hand blender will help make the process of mixing the alkaline mixture into the oil easier and faster. It is very important to mix the alkali and oil completely, so be sure to stir vigorously.

Warning

Be very careful when handling alkalis and when adding to water. Plastic gloves and a well-ventilated room are good ways to avoid burns from alkalis and harmful gases.
Castile soaps don’t produce much lather, but they clean as effectively as foaming soaps.

Things You Need

Tool

Large measuring cup
Stainless steel pot
Large plastic or glass bowl
Flour spatula
Hand blender or mixer
Meat thermometer
Scales for use in the kitchen
Plastic gloves and goggles (for alkaline handling)
Tray
Wax paper
Soap mold

Ingredient

Pure alkaline (contains in a plastic bottle, which you can store when not in use; you will need 130ml to make 10 medium bars of soap)
Olive oil
Palm oil
Coconut oil
Oil
Water

Steps