Castile Soap Recipe

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This is the first soap recipe presented on this blog. It is a basic recipe for natural olive oil soap, also known as castile soap, one of the most well-known ingredients for making handmade soap. It’s one of the simplest soap recipes. No need to purchase Castile soap when you can make it at home.

Castile Soap: the mildest soap of all

The olive oil soap, also known as Castile Soap is one of the most traditional and well known among handmade soaps. Actually, a soap is considered a Castile soap if it contains more than 70% olive oil in its recipe. This recipe, however, is 100% olive oil.

Technically, we can use any type of oil to make soap, but in fact each of them contributes with different properties to the final soap. For example, coconut oil contributes to hard bars and abundant foam, while sunflower oil contributes to softer and more moisturizing bars. However, too much coconut oil makes the skin “dry” and too much sunflower oil makes the soap bars too soft.

There are few oils that, used in 100% of the recipe, are able to produce good soaps and that is why many recipes contain such a varied mixture of oils, with well-defined quantities. The exception to the rule is olive oil and animal fat (and, surprisingly, also coconut oil). The purer the oil, the more natural and better the soap will be. For this reason, it is advisable to use extra virgin olive oil.

By itself, olive oil gives good bars of very gentle and nourishing soap for the skin without being dry, so it is especially suitable for sensitive skin. It produces a not very abundant foam that some may find “gelatinous”, others that have a creamy consistency. It does not generate abundant foam filled with bubbles like coconut oil, but there is nothing as moisturizing, silky and smooth as a bar of natural olive oil soap.

More Castile (100% Olive Oil) Recipes

More Single-Oil Recipes

Watch this video for Soap Making Safety instruction

Video in portuguese
Video in english

Watch this video for the Cold Process Soap Making tutorial

Video in portuguese
Video in english

Homemade Castile Soap Recipe

Sofia Matias
Basic recipe for a natural olive oil soap, one of the most well-known ingredients for handmade soap. In the end, you will have a very moisturizing, silky and smooth bar of soap.
Difficulty: Easy
Weight: 450g (15,8 oz)
Superfat: 5%
Lye concentration: 36%
5 from 1 vote
Prep Time 30 mins
Cook Time 30 mins
Curing Time 42 d
Total Time 42 d 1 hr
Servings 6 soap bars
Cost $14 / 12€
Cosmetic Soap Bar
Method Cold Process


  • Immersion blender
  • Pyrex or stainless steel bowl
  • Heat-resistant jug or pitcher for lye solution
  • Pitcher
  • Digital scale
  • Digital thermometer
  • Measuring spoons
  • Rubber spatula(s)
  • Small strainer
  • Cup / bottle for after trace ingredients
  • Soap mold
  • Safety goggles, gloves and mask


Lye Water

  • 103 g distilled water (3,63 oz)
  • 58 g lye (100% sodium hydroxide) (2,00 oz)
  • 1 tsp fine salt / sodium lactate


  • 450 g extra virgin olive oil (15,84 oz)

Add After Trace

  • 8 drops grapefruit seed extract (GSE) or rosemary extract (RSO) (anti-oxidant)
  • 14 ml essential oils blend (optional)

Essential Oils Blend 1

  • 7 ml essential oil eucalyptus globulus (0,25 fl oz)
  • 7 ml essential oil peppermint (0.25 fl oz)

Essential Oils Blend 2

  • 6 ml essential oil cedarwood Atlas (0,21 fl oz)
  • 8 ml essential oil lemongrass (0,28 fl oz)


Get Ready!

  • Wear goggles and gloves! Look at “Safety Recommendations” in the video above or in How to Make Soap From Scratch
  • Watch the video above about "Cold Process Soap Making tutorial" or read the post How To Make Soap by Cold Process Step-by-Step for instructions on cold process soap making before starting. These are generic but important steps for all recipes.
  • Assemble everything: ingredients, equipment, safety equipment. Prepare your workstations. Measure all the ingredients. Don’t start the recipe without having everything ready!
  • You can choose between the essential oils blend 1 or the essential oils blend 2. Do not use both at the same time.

Heat the Oils

  • Heat the olive oil to aprox. 45ºC

Prepare the Lye Water

  • Make the lye solution according to How To Make Lye Water. Add fine salt or sodium lactate in the water, before or after doing the mixture. Mix it until the vapors start to dissipate. Strain it to catch any undissolved lye crystals.

Make the Soap Batter

  • Use as a target temperature 38ºC for the oil-solution mixture. This recipe has a water discount to reduce trace time and cure time.
  • Reach trace with the immersion blender. Recipes of 100% olive oil soap take time to reach it, you may need to use the stick blender for about 10-15 minutes. In the end, it should be an opaque pale yellow batter.
  • 100% olive oil soaps take time to solidify. By using sodium lactate, your soaps will solidify faster. However, it is advisable to leave it in molds for up to 7 days.
  • After trace, add the extract and essential oils. You can choose between the essential oils blend 1 or the essential oils blend 2. Do not use both at the same time. Mix with a spoon.
  • Pour the soap batter in the molds with a pitcher (I don't recommend using box soap molds, only silicone ones). Sprinkle with alcohol or witch hazel. You can put in pre-heated oven for gel phase.

Molding and Curing


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  1. Hi Sofia, I have a sister named Sophia. Spelled with a ph though and guess what? She loves natural soaps, creams, hair products, anything natural lol.. I will share your site with her I am sure she will enjoy it. But I didn’t realize natural homemade soaps was this easy to create, seems the hardest part is the 6-8 weeks to cure. Thanks for sharing your recipes Sofia!

    1. Sofia Matias

      Hello CeCemorgan, your comment was very warming to me 😀 thanks a lot! I hope your sister checks my website and shares her experiences as well!

      Soap making is really great, but I guess it’s a passion of mine so I am biased 🙂 but yes they are much more simple to make than we think, they can easily be made at home. Here in Portugal, our grandparents used to make soap at home, with animal fat. I know you can use ashes (filtered water from grey ashes) to make soap – ashes and animal fat were by-products for many households, so it was cheap and sustainable 🙂 . Maybe if you ask your elders in the family, maybe someone remembers someone making soap at home in older times 🙂

      Cheers, Sofia

  2. Hi, I heard many years ago that making soap was easy and I knew it can be made with many soaps, but then whenever I read about this there kept being a mention of this substance called “lye” that everyone else seemed to know what it was except me. Finally – sodium hydroxide! This is very tempting to have a go at making soap but looking at the price of the ingredients I can see that this is not exactly cheap. After all, I don’t live in an olive grove so would have to buy the olive oil This does look fun though. Thanks for this. I learned something. Best regards, Andy

    1. Hello Andy and thanks for your comment.

      Soap making is relatively easy and super fun, as long as one gets over the fear to use lye, or sodium hydroxide (yes, that’s what it is 🙂 ). Besides, the resulting soap is a wonderful product to wash yourself with.

      Olive oil is in fact cheap in Portugal, around 3€/l, as we are a big producer of it. But why don’t you try this one: Homemade Coconut Oil Soap Recipe? Coconut oil seems to be relatively cheap everywhere. Use a conventional refined oil, skip scent – essential oils are the most expensive ingredients – and color – you will have a white soap – and your soap can actually be economic. Not cheap but not expensive either, and the quality is worth it.

      Best Regards,

  3. Hello! 

    I am still surprised that olive oil is used in these bars and that this is almost to the top of the list of great ingredients to be included! The benefits it gives in how it is used to solidify the soap is super interesting! I do hate that it takes soo long to get the best form to be used!

    Thank you for the information!

    Keep  Being AMAZING 

    1. Sofia Matias

      Hello Brendaliz, olive oil is a must-have ingredient in soap making 🙂 Soap made with olive oil may look a bit “creamy”, as it doesn’t foam a lot, but I simply love it and use it everyday, as it is very soft, gentle, and conditioning. 

      As for time that takes to cure, it’s true that best things in life take time to get 🙂 some soaps made with salt, might take around 6 months to cure, but I was told they are simply amazing. I am yet to experiment them. 

      Cheers, Sofia



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    The site is well designed and created, all the menus are clear plus the Title Name, But there is only one problem with the Site contents and the Menus,

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    1. Sofia Matias

      Hello, and thanks for your comment, suggestions are much appreciated. 

      Blogs are just built like that though, they are supposed to show their posts in the same main window. If you wish to open many posts in new windows you can use the “CTRL” key while clicking on the post. Hope this helps and enjoy my website.

      Cheers, Sofia

  5. 5 stars
    How easy it is to make castile soap at home!
    Thanks for this recipe!

    1. Hello and thanks for your comment!

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