Castile Soap Recipe
Home-made Castile Soap
This recipe is quick and easy to make but be sure to follow all of the following safety instructions:
- Work in a well-ventilated area to prevent being overcome by the fumes of the lye as it heats up.
- Wear the following safety gear when making soap: a long-sleeved shirt, safety goggles, and rubber gloves.
- If there are young kids running around or likely to be, leave making this soap until they're not around, for everyone's safety.
- Don't make this soap if there's a chance you'll be interrupted, as an interruption at the wrong time could ruin your soap or cause your lye solution to boil.
Table of Contents
- What is Castile Soap?
- Definitions of some soap-making terms
- Some soap-making supplies
- Rate this recipe
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.
Definitions of Some Soap-Making Terms
Lye: A mixture of sodium hydroxide/caustic soda and a liquid, usually distilled water or milk.
Saponification: The process 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.
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
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
- 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.
- Pour the olive oil into the large pot.
- Pour the demineralised water ice cubes into the small mixing bowl.
- 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.
- 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.
- 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.
- 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.
- 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.
This Is What Trace Looks Like
Below: Too Much 'Trace'
What 'Trace' Looks Like
Castile Soap Mixture in Milk Carton Molds
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