Making Castile Soap (with Pictures)

Table of contents:

Making Castile Soap (with Pictures)
Making Castile Soap (with Pictures)

Castile soap is a biodegradable soap made from olive oil, water and lye. It was invented in Aleppo and brought by the Crusaders to the Castile region of Spain, where it became very popular. For centuries, people have used this mild cleanser for everything from washing hair and skin to cleaning clothes and floors. If you've made castile soap bars, you can use them in solid form, or you can dissolve them in water to get liquid soap. Continue to Step 1 to learn how to make your own castile soap.


Part 1 of 4: Getting the supplies ready

Make Castile Soap Step 1

Step 1. Have all the supplies ready

Prepare a work area in the kitchen or other place where you have running water and arrange everything so that it is within reach. The bowls, measuring cups and other tools should only be used for soap making - do not use them after this when preparing food, as soap residue may remain in them. To make castile soap you need the following:

  • Large measuring cup
  • Stainless steel pan
  • Big scale
  • Spatula
  • Hand or immersion blender
  • Meat thermometer
  • kitchen scale
  • Rubber gloves and safety glasses (for working with the lye)
  • Lye. This is available under the name Sodium Hydroxide, also known as caustic or caustic soda. It is often used as a drain unblocker, for example, take a look at Kruidvat. You buy it in the form of crystals and what you don't use you can just keep. To make 10 medium-sized blocks of soap, you need 123 grams of lye.
Make Castile Soap Step 2

Step 2. Prepare your oil

Real Castile soap is made from 100% olive oil, but many soap makers mix all kinds of oil to get a balanced end product. Pure olive oil does not give a creamy foam, but gives a soap that is somewhat slimy in texture. Coconut oil is often added because it gives you a better lather, and palm oil can make the soap a bit firmer. A ratio of 8 parts olive oil, 1 part coconut oil and 1 part palm oil gives a nice soap. For the recipe below you need to measure the following oils. You will eventually have 1 liter of oil in total:

  • 800 ml olive oil
  • 100 ml coconut oil
  • 100 ml palm oil
Make Castile Soap Step 3

Step 3. Decide if you want to use essential oil

If you want to make your soap smell nice, add 10 drops of your favorite essential oil, or a combination of different oils. If you like a stronger scent, add more drops, if you want less, just use 5-7 drops. Essential oils commonly used in Castile soap are:

  • Peppermint
  • Orange, lemon or grapefruit
  • Lavender
  • Rose
  • lemongrass
  • Pine tree
  • sandalwood
  • Bergamot
Make Castile Soap Step 4

Step 4. Get the soap mold ready

The mold you use determines the size and shape of the soap blocks. If you want rectangular blocks, use a rectangular mold such as a cake tin; the soap then comes out as an elongated block and you cut it into blocks of the desired thickness. Line the mold with baking paper so that the soap comes out easily.

  • There are also special molds for making soap at hobby shops, and you can also find all kinds on the internet.
  • If you don't feel like buying a mold, you can use an old shoebox. Find a sturdy shoebox, reinforce the corners with tape so that the seams are closed and line it with baking paper.
  • You can also make a soap mold from wood, or use an existing wooden box as a mold.

Part 2 of 4: Mixing the lye with the oil

Make Castile Soap Step 5

Step 1. Put on your safety gear

Lye is a corrosive substance that can burn the skin and eyes, and it is bad for your lungs if you inhale it. If you're working with lye for the first time, be extra careful to do it safely. Put on rubber gloves and goggles before opening the lye package. Open the windows or turn on the extractor so that the room is well ventilated.

  • Keep a bottle of white vinegar handy. If you spill lye on the counter, vinegar can neutralize it.
  • If you accidentally get lye on your skin or have inhaled its fumes too much, call your doctor or 911.
Make Castile Soap Step 6

Step 2. Make the lye solution

When mixing lye and water, it is important to know the correct proportions. For this recipe you need 296 ml of water and 123 grams of lye. Use separate containers to measure it accurately with the kitchen scale. Carefully add the lye to the water. The mixture will immediately become hot and look cloudy. When it cools down, it gets a little brighter again. It takes a few minutes to cool down. Use the meat thermometer to check the temperature. The lye is ready to use when it is 50°C.

  • Never add the water to the lye - always add the lye to the water. If you pour water over the lye, you can get an explosive reaction.
  • When weighing the ingredients, make sure you don't include the weight of the containers.
  • If you want to make more or less soap, use a lye calculator to calculate the exact amounts of water and lye.
Make Castile Soap Step 7

Step 3. Heat the oil

While the lye cools, heat the oil. Put them in a pan and place it on medium heat. Stir the oil well so that the different types are mixed. Keep heating it until the oil is 50°C. Use the meat thermometer to check the temperature. The oil and lye should be as close to the same temperature as possible when you put them together.

If you don't make sure the oil and lye are the same temperature, the soap won't set properly. Be sure to use the meat thermometer to check both mixtures to complete this crucial step

Make Castile Soap Step 8

Step 4. Mix the lye with the oil

Pour the lye mixture into the oil mixture. Use a mixer or stick blender to mix it well. After a few minutes the mixture will thicken. At a certain point the mixer leaves a trace in the mixture, this is called the "trace phase". It should now have the consistency of honey.

You can also stir the lye and oil with a spoon, but it will take much longer to reach the "trace" stage

Make Castile Soap Step 9

Step 5. Add the essential oil

When the mixture has reached the trace phase you can add the essential oil. Put 10 drops of essential oil in the pan and mix with the mixer until well distributed.

Part 3 of 4: Pouring the soap and letting it mature

Make Castile Soap Step 10

Step 1. Pour the soap into the mold

Be careful not to mess. Cover the mold with a clean tea towel or towel, taking care not to let the cloth touch the soap itself, but drape it over the sides of the mold. This way you protect the soap against dust and insects. Leave it for 48 hours.

  • During these first 48 hours, the soap will solidify and harden. However, it is not ready to use yet; it must first mature so that the water can evaporate from it and the soap becomes milder. Do not touch the soap yet, as the lye may still bite at this point.
  • Check the top of the soap after 48 hours. If it is coated or looks like it has separated, the soap is not usable. You've used too much lye, which can irritate the skin, or the lye and oil aren't mixed well. Unfortunately, the soap cannot be saved, you will have to throw it away and start over.
Make Castile Soap Step 11

Step 2. Remove the soap from the mold

A store-bought mold will likely have sides that you can take off so that the soap comes out easily. If you used a shoebox, you can tip the soap out, or cut the sides off. If you used a cake tin, simply turn it over.

Make Castile Soap Step 12

Step 3. Cut the soap into pieces

Decide how thick you want the pieces to be. About 2-3cm is standard, but you can make it thicker or thinner if you like. Use a ruler to measure the thickness and mark evenly spaced marks on the soap so you know where to cut. To cut the soap you have the following options:

  • Use a sharp knife. Don't use a serrated knife unless you want the soap to have wavy sides.
  • A dough cutter. This also works well for cutting soap.
  • A cutting wire. Make sure the wire is straight, then you get nice straight pieces.
Make Castile Soap Step 13

Step 4. Place the bars of soap side by side to mature

Place a piece of baking paper on a plate or board and place the bars of soap on it. Place it in a cool, dry place and let it mature for at least 2 weeks to a maximum of 9 months. The longer you wait, the better the soap will be; you get a creamier foam and a better texture.

After a few weeks you can start using the soap. When the soap is ready, it is firm and there is no longer any chemical smell

Part 4 of 4: Making Liquid Castile Soap

Make Castile Soap Step 14

Step 1. Grate 100 grams of Castile soap

This is an average bar of soap. Use a cheese grater or a fork to grate it into small pieces. The soap will then dissolve more easily in water.

Make Castile Soap Step 15

Step 2. Bring 2 liters of water to a boil

Pour it into a pan and put it on high heat. Bring the water to a boil.

Make Castile Soap Step 16

Step 3. Combine the soap flakes and water

Pour the water into a large plastic bowl or pitcher and stir in the soap flakes. Let the mixture sit for a few hours until it thickens. If the soap gets too thick, reheat it and add a little more water. It should have the consistency of shampoo.

Make Castile Soap Step 17

Step 4. Pour it into bottles

Pour the liquid soap into squeeze bottles and keep them in the kitchen or bathroom. The liquid soap stays good for months at room temperature. Use it to wash your hair and skin, or to clean your clothes, dishes and other things around the house.


  • Experiment with essential oils such as lavender, eucalyptus or orange for a wonderful scent.
  • If you want to change the texture, hardness or smell of the soap, you can adjust the proportions of the base ingredients a bit. It's always better to start with a little less lye, and then try a little more if the soap doesn't work, than the other way around.
  • Mixing the lye solution and the oil is a lot easier and faster with a stick blender. It should be really well mixed, so stir it vigorously.


  • Be very careful when you put the lye in the water. Rubber gloves, safety glasses and a well-ventilated area are essential.
  • Castile soap doesn't foam as much, but it cleans just as well as soap that does foam a lot.

Popular by topic