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This DIY liquid castile soap recipe is easy and inexpensive to make. It’s a great multipurpose cleaner, perfect for both your body and around the house!
A couple of years ago, I showed you how easy it was to make a basic beginner soap, even if you’ve never done it before. I understand why making soap can sound intimidating, but once you give it a try, it can become very addicting. Seriously, not only is it a pretty thrifty hobby because you can make large batches that will last you a long time, but it’s fun to be able to customize the soap to be exactly the way you want it and not depend upon what’s on the market.
Even if you’re just a beginner, it’s easy enough to change up your soap by only using different essential oils, or exfoliants like poppy seeds, or other fun ingredients without having to do a lot of research into making a new viable recipe. As you get more experienced, you’ll probably want to take things a step forward and make new recipes of your own and add in milk or pumpkin or spices and colorants. Once you learn how to use a soap calculator, that isn’t really that difficult either.
But maybe, you’d just prefer something a little different?
A liquid soap perhaps?
I’ll have to admit that I was making soap for a very long time before I started making liquid soaps and coming up with a DIY liquid castile soap recipe for you to try. There aren’t as many resources available for making liquid soaps, so it’s a bit of trial and error at first, but once you find a recipe that works out well, it’s pretty simple to make. While it does take a little more time and effort than whipping up a batch of bars of soap, I think you’ll find that it’s well worth it, especially when you take a look at the price of a store bought liquid castile soap.
I want to call special attention to something. When making liquid soaps, you use KOH, potassium hydroxide, rather than NaOH, sodium hydroxide, the lye used in bar soaps like my easy, beginner soap.
What is castile soap?
Technically, Castile soap is a type of soap made with only olive oil, whose name originates here in Spain. (You can read more about the origin of Castile soap and other other soaps in my recipe for pure Castile bar soap.) Over the years, the definition of Castile soap has broadened to include other types of vegetable oils such as coconut oil. Dr. Bronner’s Soap, which has probably become the most famous commercial liquid castile soap, even has a greater percentage of coconut oil than olive oil.
When it comes to making a homemade castile soap, though, I was a bit of a purist, and wanted it to be the real deal and made with only olive oil.
Why did I decide to make a pure, liquid castile soap?
The great thing about liquid soaps over bars of soap, is that it is very versatile and you can make several different types and then mix them to the perfect combination for you after having made them!
Soaps made with different oils have different properties.
Soaps made with olive oil, for example, tend to be more hydrating for your skin than soaps made with coconut oil. On the other hand, they don’t lather up as much as a coconut oil soap, nor do they leave you feeling squeaky clean in the same way (partly because they are more hydrating). Pure coconut oil soaps tend to be great for cleaning around the house and for laundry. Pure olive oil soaps tend to be gentle on the skin and great for gentle body cleansing.
The ideal solution would really be to combine different oils when making your soap to get the qualities you want from the various oils you use. That’s exactly what they did when they formulated Dr. Bronner’s soap, and what I did when I showed you how to make a basic beginner soap using a combination of olive oil and coconut oil.
When you’re making a bar of soap, you have to decide what combination you want to use from the very beginning, and your entire batch will have that very same combination.
With liquid soaps, though, you have the advantage of being able to combine your various soaps after the fact, making it easier to experiment with smaller combinations until you find the perfect soap for your need.
That’s why I made a pure liquid castile soap, using only olive oil, and then later made a pure liquid coconut oil soap (recipe here) and I mix them together in differing quantities depending on how I want to use each soap.
The other great thing about making liquid soap is that, unlike with bar soap, you can also add in your additives like essential oils after the fact. This means that you don’t have to divide your batch at trace and work quickly to mix in your different essential oils to each part before the soap sets up. I, instead, make a concentrated liquid soap base, and as I dilute it and mix it using soaps made with various oils, I also decide what essential oils I want to add. This gives me the freedom even months after having made my soap base, to play with fun combinations.
So have I convinced you to give it a shot?
I hope so!
Easy, beginner, DIY liquid castile soap from scratch!
Easy DIY Liquid Castile Soap Recipe
Makes 1-2 gallons of liquid soap. (See notes below)
Materials
Instructions
- Measure out the olive oil and begin to heat it over low heat. I warmed mine on the low setting of my slow cooker. A slow cooker is perfect for this sort of job because it will gently warm without burning, and keeping things at a steady temperature. (In the picture you can see that I first thought to try using a glass bowl in my slow cooker as a sort of double boiler, but I later found it too difficult and just poured the ingredients directly in the slow cooker itself.
- Mix together the glycerine and water, and measure out the potassium hydroxide (KOH).
- Carefully add the KOH to the water (and not the other way around!) in a well ventilated area. I usually do this outside. Stir the KOH into the water until it dissolves. It will be cloudy at first, but then it will clear up.
- Slowly add in the the KOH mixture to the warm olive oil, and slowly stir them together in the slow cooker over low heat to incorporate the lye mixture into the oils.
- Using a hand held blender, begin to blend the ingredients together in the slow cooker. In a few minutes the mixture will begin to thicken and look like mayonnaise, and then just moments later will look like a creamy pudding.
- A couple of minutes later, the mixture will begin to look grainy. A lot of people call this the mashed potatoes stage because that's sort of what the mixture resembles. Continue to blend. (If at any point the mixture becomes too thick to blend with the hand held blender, switch to mixing with a wooden spoon, but when working with only olive oil I found the mixture to be pretty workable throughout the process.)
- As you continue to blend, it will start to get creamy again, and you will notice that you will start to see translucent streaks in your mixture. Once you reach this point, you can stop blending with the hand held blender, and begin to stir occasionally with a wooden spoon.
- The mixture will begin to thicken up and become more translucent. We are now working on making a soap base paste which will be dissolved into a clear liquid soap. The process will take 3-4 hours, and you will want to check on it and stir it up every half an hour or so. (See, I told you this takes a bit longer than making bar soap, but the results are worth it!!)
- To check for "doneness," we will look to see if our paste is dissolving into a completely clear liquid soap. To do this, take a small amount of the soap paste and dissolve it in water, and look to see if the water is clear once the soap paste is dissolved. If the liquid is cloudy, you will want to continue to cook the soap in the slow cooker. You can let it cook another half an hour before checking on it again. If it dissolves clear like the soap in my picture, you are finished making the soap paste.
- Your liquid castile soap paste is now ready to be stored or dissolved into liquid soap as needed.
Notes
- This recipe makes 4.5-5 lbs. soap paste which can be diluted to 10-20 lbs. soap or more. That ends up being 1-2 gallons, or more, depending upon desired concentration.
- Keep in mind that liquid soap is not as thick as commercial gels and surfactants. Liquid soap is of a thinner consistency, and doesn't need to be thick to be concentrated and work well.
Diluting your soap paste
Once you have made your soap paste, you’ll need to dilute it as needed to get your liquid soap. For that, you’ll need to take some of the paste and let it dissolve into water over the course of several hours or over the stove. I used distilled water for my liquid soap to help make sure it will last as long as possible, but for small batches that are going to be used relatively quickly, you can probably get away with tap water without any issues. You can read more about how to dilute a soap paste here.
When I made my first batches last fall, I diluted my various soaps into thick, clear liquid soaps, but was disappointed to find that a week or two later, they started to turn opaque and much thicker.
Why did my DIY liquid soap turn opaque?
It turns out that as the weather got colder, my soaps turned more opaque and thicker just like coconut oil solidifies when in a cold environment!
I wouldn’t have been surprised that the coconut oil soap did that, but my beginner liquid castile soap did the exact same thing!!
I had my suspicions that that was the issue, but wasn’t able to confirm it until this spring when some of my thicker liquid soaps, left as is as an experiment, turned perfectly clear and beautiful again. (update: this winter, my soap has become very thick, opaque and a bit gloopy again. Keep this in mind if you are making this soap in winter!)
So, does that mean you can’t use homemade liquid soap in the winter/cold environments?
No.
You can still use your soap, you’ll just need to dilute it a little more. I haven’t provided an exact amount of water to use for dilution because I’ve found that it depends upon the temperature outside, and what I’m looking for in consistency for each particular use of the soap.
I was curious to compare, so I recently bought some of Dr. Bronner’s soap to compare with mine, and I have noticed that the soap I bought was also quite a thin, diluted consistency. After some reading, I’ve learned that most commercial liquid soaps are later thickened with added ingredients. I prefer to keep mine as natural as possible, so I leave it as is… diluted until transparent and usable in a soap pump.
In the winter, then, my soap is a little bit thinner than it is in the summer, but that isn’t a problem for me.
Why did I add glycerin to the recipe?
This question has come up several times, so I thought it was best to update this post with an answer.
When I first wrote the post, I had studied several methods of making liquid soaps. One is called the glycerin method, and replaces part of the water with glycerin. In theory, that is done to help move the process along and make the liquid soap paste process more quickly. Because this was meant to be a beginner liquid soap recipe, I wanted things to be as quick and fool proof as possible, so I chose the glycerin method.
In the end, I don’t know if it really makes the process quicker and easier or not, but I have found several benefits to adding glycerin to the recipe:
- The resulting soap paste dissolves very easily in water. I don’t need to heat the water nor do I need to leave it for days at a time. I can cover my soap paste with distilled water and in a couple of hours I have a beautiful, clear liquid soap effortlessly.
- I find that even my liquid coconut oil soap is hydrating enough to use on the body despite the fact that it hasn’t been superfatted at all. I think the extra glycerin helps to make a really great, hydrating soap that is clear and doesn’t need extra oils. (I think that’s also why my homemade glycerin bar soap is hydrating even without superfatting at all.)
My DIY liquid body soap recipe:
60-70% liquid castile soap (made with olive oil)
30-40% liquid coconut oil soap (for lather, link goes to the recipe post)
Essential oils of choice.
I mix all of the ingredients together, and keep a bottle in the shower to use instead of shower gel.
I like to switch up the essential oils used in each batch, and have so far tried adding lavender essential oil with a bit of tea tree oil in one batch, and a citrus blend using lemon and bergamot in another.
I’d love to hear what blends are your favorites.
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Hi Tracy,
How long do you keep the mixture on the heat for? Is it until the mixture dissolves clear ( few hours in your recipe)?
I live in Bangkok and castile soap is very expensive here so i want to make it myself, but have never done anything like this before. Many thanks
Hi Sally,
Yes, that’s what I normally advise. When you see it becoming translucent, then you should be good to go.
In some cases, it will continue to be slightly cloudy, but should still work fine. It may clear up with time on its own.
Hello Tracy,
I want to make other oil.
We can calculate the amount of oil and KOH.
( What percentage of KOH is over? )
What percentage of water and glycerin do you put in?
Hi Jihyun,
I use the SBM Crafters advanced soap calculator when making liquid soap. They have a setting for using glycerin. I don’t superfat my liquid soaps to keep them from getting cloudy.
Hello, Can I use avocado oil instead of olive oil for this recipe?
Any changes to the oil need to be run through a lye calculator because each fat needs a different amount of lye. The different oils also have different properties in the final soap. For bar soaps, most liquid oils aren’t good to use as the only oil in the recipe. Olive oil is kind of an exception, and even then not everybody loves soaps made with only olive oil.
I’ve never made a liquid soap with avocado oil, so I’m not sure what would happen if you were to make an avocado oil liquid soap.
I’ve tried this soap twice now, and I love the result! However, making it is never straightforward for me. It always takes me three times as long (or more!) to reach the mashed-potato stage than you recommend. I also have struggled to get to the point where there are translucent streaks. Sometimes the whole thing just thickens up again to the point where it’s super hard to stir. Am I doing something wrong?
Hi Braeden,
Hmmm- that’s interesting.
I doubt you’re doing anything wrong.
I wonder if it’s due to a difference in the olive oil or if it’s a difference in the crockpot. Mine admittedly gets quite hot, so maybe mine cooks it at a higher temperature than some others?
I live in Spain so I also have access to pure and high-quality olive oil. I’ve heard some people complain that some olive oils aren’t as pure as they should be. If that’s true, it could be a possible “problem” when making soap because each fat has a different saponification value and behaves in a different way when used to make soap.
In any case, I’ve found that eventually, the soap paste will turn transparent on its own with time. So, even if you were to stop the cooking process earlier, if you aren’t in a hurry to use it, it would probably eventually finish up on its own.
Thank you Tracy!!!
Another question:
How do you Store the Soap Paste?
~Lietzah
Hello Tracy,
This is my first time making this!!! I have found the process to be quite fun!!! I was wondering if this soap can also be used for body soap, correct? Just asking since you have a recipe for body soap… But it seems like it maybe just another recipe to try…
~Lietzah
Hello Lietzah,
Yes, definitely!
I have used this for our body soap for years now. (In fact, even the liquid soap made with coconut oil is mild enough for body use, I think.)
I want to make a main article about making liquid soap and will talk more about my findings and how I use the soaps.
Thank you Tracy!!!
Another question:
How do you Store the Soap Paste?
~Lietzah