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Castile Soap Recipe

Updated on December 15, 2015

Home-made Castile Soap

Source

Safety first

This recipe is quick and easy to make but be sure to follow all of the following safety instructions:

1. Work in a well ventilated area to prevent being overcome by the fumes of the lye as it heats up.
2. Wear the following safety gear when making soap: a long-sleeved shirt, safety goggles and rubber gloves.
3. If there are young kids running around or likely to be, leave making this soap until they're not around, for everyone's safety.
4. Don't make this soap if there's a chance you'll be interupted, as an interuption at the wrong time could ruin your soap or cause your lye solution to boil.

What is Castile soap?

Castile soap is one of the purest soaps you'll find because its only active ingredient is Olive oil.

Sure you use Lye to make soap, but lye is only active until saponification occurs, so really, all you have in the soap after that is Olive oil.

Castile soap is a highly moisturizing soap that creates a creamy lather rather than a foamy one. You'll still get a great clean and you'll be moisturizing your skin at the same time. In fact you'll feel a slightly oily film on your skin after you shower with Castile soap. Don't be repulsed by this, it's part of the charm of Castile soap.

This soap is vegetarian and vegan friendly.

All the photos in this article were taken by me.

My other soap recipe

Coconut-milk soap recipe

I've also written a recipe for making coconut-milk soap.

Definitions of some soap-making terms

Lye: A mixture of sodium hydroxide/caustic soda and a liquid, usually distilled water or milk.

Saponification: when lye and fat/oil react together to form soap.

Trace: The stage in the soap making process where saponification is achieved. This can be seen when the soap mixture is of a custard-like consistency and marks/traces are left behind in the mixture when the tip of a knife or spatula is run through it. If you carefuly pick-up some of the mixture with the spatula and let it drip back down into the bowl, it will also leave traces/marks in the mixture. The pictures on the right show examples of this. The one on top shows a perfect trace. The one below shows what happens if you don't pour the soap into molds immediately after trace - the soap has started to set. This will make it harder to pour into molds - not impossible but harder - and it will not give you smooth looking bars.

Equipment

To make Castile soap you'll need the following equipment:

Rubber gloves

Molds (clean empty milk cartons are fine)

A large pot that's around one foot deep - stainless steel or plastic (a bucket is fine) - needs to be deep enough to prevent spillage and contain splashes so you don't get burnt by the lye. One with a handle is ideal or one that doesn't weigh much as you'll have to handle it by the top or the handle since the lye mixture inside will be quite hot. I don't recommend a metal bowl for this.

A mixing bowl of at least 2 litres capacity (an ice-cream container is fine)

Digital kitchen scale to weigh your ingredients, precise to 1gram.

Measuring jug to measure the water.

1 or 2 spatulas

stick blender

safety goggles

DO NOT use any equipment made of aluminium or tin as they may react with the lye, this includes your mold(s).

Keep these items separate and use them only for soap-making. The scale is an exception, simply cover it with clear food wrap when using it for soap-making to keep it clean and prevent any caustic soda contaminating its surface.

Equipment for castile soap

Above: Equipment for Castile soap
Above: Equipment for Castile soap | Source

Ingredients For Castile Soap - This Recipe Produces 2130g Of Soap.

  • 1500g (yes that's right, grams) Olive oil, Pomace or pure. Avoid virgin and extra virgin. You have a 10g margin of error on either side.
  • 440g (yes, grams again) distilled/demineralised water, Measured the weight of the water then pour into ice cube trays to make ice cubes with it.
  • 189g to 190g caustic soda/sodium hydroxide, Must be anywhere within the amount stated - not above, not below

Ingredients for Castile soap

Above: Ingredients for Castile Soap
Above: Ingredients for Castile Soap | Source

Instructions

  1. Follow my instructions precisely and you'll end up with around 2.1kgs of lovely, creamy, moisturising Castile soap. PLEASE READ THE SAFETY INSTRUCTIONS AT THE TOP OF THIS PAGE FIRST IF YOU HAVEN'T ALREADY DONE SO.
  2. Pour the olive oil into the large pot.
  3. Pour the demineralised water ice cubes into the small mixing bowl.
  4. Add the caustic soda/sodium hydroxide to the ice cubes and stir until the caustic soda is fully dissolved and the ice cubes have completely melted (do not add the water to the caustic soda, this will cause a violent reaction much like a volcano). You now have your lye mixutre. It could still get very hot so do not let it come into contact with your skin or eyes as it could cause serious burns.
  5. Gently pour the lye mixture into the pot with the olive oil. Lower the small mixing bowl into the large pot, don't tip it in from over the top of the pot as it could splash. Be careful when handling the mixing bowl so you don't burn your hands, especially if it's starting to boil. I've never had that happen to me but I've heard it can happen. The reason I use ice cubes water is because it takes longer for the lye to heat up, giving me enough time to work. Never leave the lye mixture sitting in the bowl unsupervised.
  6. Blend with the blending stick on the highest speed until you reach trace (see definitions above and video and photos below), then promptly pour the soap mixture into your mold(s). Use the second spatula to scrape any mixture from the bowl, some of this can often equal a couple of bars so you really want to get it all. When blending it's important to hold the blending stick in a vertical position for the duration of the mixing to minimize any spraying. This should contain any spray to the inside of the pot.
  7. Leave the soap to set for 48 hours then remove from molds and place on paper towels. Leave there to cure for 6 weeks, turning the bars over once a week. Cutting: If you made a loaf bar, such as the ones I made in the milk cartons, carefully remove it from the mold 36 hours after pouring, to cut it as desired. The soap will still be quite soft at this stage so be careful when handling it. Don't attempt to cut it earlier or later as it will be too soft if done too early and too hard if done too late to get a clean cut. 36 hours is ideal. Use a bread knife for best results.
  8. The soap is ready to use once it has hardened but at this stage it's still pretty harsh on skin. It's best to leave it to cure for at least 6 weeks, during this time the pH will lower and water will evaporate from the soap, creating a milder, harder, longer-lasting bar. Never leave this soap to sit on a wet surface when you have finished in the shower, as it will dissolve into a globby mess. Hand-made soap still contains all its glycerin, unlike most commercial soaps, this is what causes it to dissolve quickly when constantly wet. Keep it dry between uses to prolong its life.

Below - This Is What Trace Looks Like.

Above: You'll know you have achieved 'trace' when you can leave a line in the soap mix by running the tip of a knife or spatula through it.
Above: You'll know you have achieved 'trace' when you can leave a line in the soap mix by running the tip of a knife or spatula through it. | Source

Below: Too much 'trace'

Above: This happens when blending has gone for too long or the soap hasn't been poured fast enough after reaching trace. You can still use it but you might need a ladle to spoon it into your moulds.
Above: This happens when blending has gone for too long or the soap hasn't been poured fast enough after reaching trace. You can still use it but you might need a ladle to spoon it into your moulds. | Source

What 'trace' looks like

Castile soap mixture in milk carton molds

Above: Castile soap setting in milk carton molds. 36 hours after pouring, tear off the carton to be left with 'loaves' that you can slice easily with a bread knife. Note: wash milk cartons in soapy water, rinse clean and dry well before using them.
Above: Castile soap setting in milk carton molds. 36 hours after pouring, tear off the carton to be left with 'loaves' that you can slice easily with a bread knife. Note: wash milk cartons in soapy water, rinse clean and dry well before using them. | Source
Above: Bars of Castile soap which will be left to cure for at least 6 weeks.
Above: Bars of Castile soap which will be left to cure for at least 6 weeks. | Source

Please share this article if you find it helpful

Please share this article on Facebook, Twitter and Pinterest in you find it helpful. Let me know if you did in the comments box below so I can thank you. You can also rate this article below it and leave a comment in the comments box at the bottom of this page. I appreciate all comments and suggestions and I reply to all of them.

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    • sleepylog profile image
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      Sleepylog 2 years ago from Australia

      Thank you so much BG! I'm so glad I could help you :)

    • profile image

      BG 2 years ago

      This is a wonderful tutorial! I've always wanted to know how to make castille soap, and with your instructions, now i finally do. :) I'm pinning this on Pinterest. Thank you so much for the information!!

    • sleepylog profile image
      Author

      Sleepylog 2 years ago from Australia

      Thank you for the compliment Rachel. To answer your question: you would add the essential oil at trace, not before. You will have to work quickly to blend it in.

    • profile image

      Rachel Washington 2 years ago

      Hello! Thank you for such a comprehensive and well explained article! I have a question: Can I add essential oil (drops) at any point if I would like the soap to be scented? If so, when exactly should I add that?

    • JessicaBarst profile image

      Jessica Barst 3 years ago from Dallas, TX

      Wow, this is great! I have a recipe for a homemade shampoo that calls for castile soap, and it's even more exciting that I can make the main ingredient for that myself too.

      By the way, really like the way you use a Table of Contents. That will come in very handy when it's time to go back and follow the recipe.

      I am really looking forward to trying this. I had no idea olive oil was a component of castile soap!

      Thanks! I'm pinning this for later :)

    • profile image

      Grey 3 years ago

      These are great and wonderfully detailed tutorials! Thank you!

    • sleepylog profile image
      Author

      Sleepylog 3 years ago from Australia

      It's possible but it's a matter or trial and error. You would need to add water and heat the soap up to melt it so the water can be mixed into it. If you cut the soap it will mix faster. As it cools it will harden again. You'll need to keep doing it until the soap no longer hardens, this will mean there is enough water mixed into it. Better to start with small amounts of water until you get the desired consistency. Let me just warn you that it's an extremely time consuming project. Let me know how you go if you decide to attempt it.

    • profile image

      CC 3 years ago

      Can you turn this into a liquid soap?

    • sleepylog profile image
      Author

      Sleepylog 4 years ago from Australia

      I think one cup is about 250mls and 1500 is approximately 1500mls of Olive oil, but it's not exact so you'll still have to weigh it, but to answer your question, it would be around 6 cups.

    • profile image

      Kristin 4 years ago

      Approximately how may cups Is 1500 grams of olive oil? I'm going to weigh it when I make it but I just want to make sure that I buy enough