Homemade Hot Process Castile Soap Recipe for Bars or Liquid

Updated on November 27, 2017
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Rachel is a soap-making, wine-making small farmer living in Minnesota with her husband, their sheep, and their blue heeler pup.

Bars of Castile soap.
Bars of Castile soap. | Source

Castile Soap

Castile soap has been all the rage on social media for a while now, and I've seen quite a few recipes being shared so that people can avoid buying the expensive product from big stores. But the thing is, pure Castile soap, unlike what you buy in the store, is traditionally made from 100% olive oil - which doesn't actually make soap that's all that great. A really good bar of soap is made using a variety of oils that each bring a different trait to the table.

I worked out a simple recipe that is still considered Castile soap because it is more than 50% olive oil, but it incorporates other oils as well, to create a much more balanced, cleansing, and bubbly soap!

If you make your own laundry soap, you will also love this recipe for your laundry bars.

This Castile recipe calls for olive oil, coconut oil, castor oil, water, and pure lye (often called sodium hydroxide) and will make about two and a half pounds of soap. If you like to use lard to make soap (I sure do!), I have an alternate recipe for Castile soap made with lard included here for you as well.

Basic Soap-Making Safety

I recommend reading my article Homemade Soap Made Easy if this is your first time making soap.

Making real soap requires the use of lye (sodium hydroxide), which is a caustic base, so you need to exercise some safety precautions.

When I make soap, I use the following to protect by skin and eyes:

  • Goggles while handling lye
  • Large rubber gloves while handling lye and the soap until it comes out of the mold
  • Long sleeves and pants

If you do get any lye on your skin, don't panic - just splash it off with some pure white vinegar (an acid that will neutralize the basic lye) and then cleanse your skin thoroughly under running water. Keep pets away from soap-making, and use caution and common sense if you want your children involved in the process with you!

Homemade Castile Soap Recipe

Please note: All measurements are by weight, NOT by liquid volume.

Ingredients:

  • Olive Oil, pure (not Extra Virgin), 24.5 ounces
  • Coconut Oil, 5.5 ounces
  • Castor Oil, 1.5
  • Pure Lye, 4.0 ounces
  • Water, 10.0 ounces
  • Essential oil or Fragrance oil (optional), 1-2 ounces stirred in before molding

Instructions:

  1. In a large non-reactive metal pot, combine the first three ingredients and warm gently, stirring occasionally. The coconut oil needs to melt into a liquid.
  2. Bring the oil mixture to about 115* Fahrenheit.
  3. In a glass jar, add the water. This is important. You must add the water to the jar BEFORE adding the lye to avoid a potential hazard.
  4. Add the lye crystals to the water and stir with a glass or other non-reactive rod or spoon until all the lye has been dissolved.
  5. When all the lye has been dissolved, add the lye solution to the hot oil mixture and stir well.
  6. Stir the soap mixture briskly until it reaches trace. You may want to use an immersion blender to speed up this process.
  7. Once trace is achieved, pour the hot soap mixture carefully into your crock pot. Set the crock pot to high and prepare to watch the cook.

Cooking the Castile Soap

  1. Set your crock pot to the high setting for about 10 minutes, then reduce the heat.
  2. Stir the soap when the edges begin to "creep" up the sides of the crock only enough to keep it from getting out of the crock.
  3. Observe the soap reach a semi-translucent, "applesauce" state, and prepare the mold to plan to put the soap into.
  4. When the soap reaches a semi-translucent, mashed potato-looking state, it is done cooking and ready to go into the mold. You can test doneness by stirring it briskly just a couple of times and watching to see if there is any separation of oils out of the soap mixture.
  5. If using the optional Essential/Fragrance oil, stir in now.
  6. Spoon the hot soap into the mold. It should be quite thick and goopy.

Note: Over-stirring hot process soap can, in my experience, result in unsightly air bubbles and just a general lack of density in the finished soap bars.

There is no need to cover the hot soap once you have put it in the mold. It is fully saponified at this point, meaning no further chemical reaction is in progress, and its only job now is to cool down so that it can be cut into bars!

Click Though for a Photo Version of My Hot Process Castile Soap Instructions!

Click thumbnail to view full-size
Combine all oils in a nonreactive pot and heat to about 115* F.Stir or blend until the pudding-like consistency known as trace is achieved. Pour the traced soap mixture into a crock pot and begin heating. Notice how the mixture begins to thicken as heat is applied to the reaction.Cook until the "applesauce" stage is reached and prepare your mold. You're almost done, but not quite - keep cooking and watching your soap!When your soap reaches the "mashed potato" stage as seen here, it is done cooking and ready to be molded! Spoon your cooked soap into a mold. For hot process soap, you can be like me and use a simple, cheap rubber mold liner propped up by a cupboard and books ;)
Combine all oils in a nonreactive pot and heat to about 115* F.
Combine all oils in a nonreactive pot and heat to about 115* F. | Source
Stir or blend until the pudding-like consistency known as trace is achieved.
Stir or blend until the pudding-like consistency known as trace is achieved. | Source
Pour the traced soap mixture into a crock pot and begin heating. Notice how the mixture begins to thicken as heat is applied to the reaction.
Pour the traced soap mixture into a crock pot and begin heating. Notice how the mixture begins to thicken as heat is applied to the reaction. | Source
Cook until the "applesauce" stage is reached and prepare your mold. You're almost done, but not quite - keep cooking and watching your soap!
Cook until the "applesauce" stage is reached and prepare your mold. You're almost done, but not quite - keep cooking and watching your soap! | Source
When your soap reaches the "mashed potato" stage as seen here, it is done cooking and ready to be molded!
When your soap reaches the "mashed potato" stage as seen here, it is done cooking and ready to be molded! | Source
Spoon your cooked soap into a mold. For hot process soap, you can be like me and use a simple, cheap rubber mold liner propped up by a cupboard and books ;)
Spoon your cooked soap into a mold. For hot process soap, you can be like me and use a simple, cheap rubber mold liner propped up by a cupboard and books ;) | Source

Making Liquid Castile Soap From Your Castile Bars

While it's totally true that you can make liquid soap a different way, using potassium hydroxide, I made liquid soap directly from my bar soap. It's actually ridiculously easy to do!

  1. Cut one of the Castile soap bars you made into about one-ounce pieces.
  2. Take one-ounce of the Castile bar soap and grate it using a cheese or potato grater. The finer, the better!
  3. In a large metal pot, boil as close to a gallon of water as you can manage.
  4. Add the grated Castile soap when the water reaches a rapid boil.
  5. Stir until the grated soap is completely dissolved.
  6. Carefully pour the liquid soap into a bucket. If needed, top off with hot water from your faucet until you reach about one gallon.
  7. Cover the Castile liquid soap with some plastic wrap and let sit overnight.
  8. Bottle as you see fit! I like to use recycled old hand soap bottles with the pumps.

Shelf Life: Where water is involved, bacteria can be present. In general, the pH of soap prevents bacterial or fungal growth, but it's a good thing to be aware of. The bar soap you made with my recipe still contains a small percentage of unsaponified oils, and because we don't use any preservatives in our homemade soaps around here, it is possible for those oils to spoil. I would recommend only storing this liquid soap for about six months, which is why I only make one gallon of it at a time.

Alternative Castile Soap Made With Lard

This recipe makes about 2 pounds of Castile bar soap, and I must say, is a much more balanced soap than recipes that call for larger percentages of olive oil. It's my personal favorite for soap made with olive oil.

  1. Olive oil, 9.5 ounces
  2. Lard, 7.4 ounces
  3. Coconut oil, 6.0 ounces
  4. Castor oil, 1.0 ounce
  5. Water, 7.6 ounces
  6. Pure Lye, 3.3 ounces

Follow the instructions for making the first recipe to create this soap!

Alternative Cold Process Method

Either of these recipes can be used to make bar soap using the cold process method, rather than the hot process method as prescribed.

To convert these recipes to cold process, make the following changes:

  • Use about double the recommended essential or fragrance oils, unless you don't mind a weaker fragrance
  • Wait for the lye to cool down to about 110* Fahrenheit before adding it to the hot oils at the same temperature
  • Instead of pouring the soap mixture into a crock pot and cooking it, pour it directly into a mold, insulate the mold, and leave it alone for 12-24 hours
  • Cure the cold process Castile soap bars for 3-7 days before testing them for hardness

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