Made with only olive oil, this pure liquid Castile soap is easy to make and mild. It’s perfect for face and body, and for cleaning 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.
Making solid soaps can be a lot of fun, but not everybody likes using bar soap. Many people prefer using something in a dispenser like a shower gel or a liquid soap.
I made many different types of bar soaps before attempting to make a true liquid soap. There aren’t as many resources about making liquid soaps, so I had to do a lot of trial and error before posting this first liquid Castile soap recipe.
Once you find a good recipe, it’s pretty simple to make. While it does take a little more time and effort than whipping up some bars of cold process 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.
How does liquid soap differ from bar soap?
The main difference between bar soaps and liquid soaps is the type of lye used to make them. Liquid soaps are made with KOH, or potassium hydroxide, rather than NaOH, or sodium hydroxide.
You can read more about the different types of lye in my post about lye and why it is needed in soap.
While some people like to make a “liquid soap” of sorts by diluting bar soaps in water, you can’t really get a true, transparent liquid soap that way. Some people are happy with the result, but every time I’ve tried it, I’ve ended up with a gloopy mess. It doesn’t have the same cleaning power as either a bar soap or a true liquid soap, and the texture and appearance aren’t the same either.
What is pure Castile soap?
Technically, by definition, Castile soap is a type of soap made with only olive oil. The name “Castile” soap originates here in Spain. (You can read more about the origin of Castile soap and other soaps in my post with a 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 liquid Soap, which may be the most famous commercial liquid Castile soap, actually has a greater percentage of coconut oil than olive oil. (I made a Dr. Bronners liquid Castile soap copycat recipe for those who are interested!)
When it came to making a homemade liquid Castile soap, though, I was a bit of a purist and made the real deal: a soap made with only olive oil.
Olive oil in soap
Soaps made with different oils have different properties.
Soaps made with olive oil are more conditioning 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 conditioning).
Some people find pure Castile bar soap to be “slimy” and not cleansing enough. On the other hand, pure coconut oil bar soap can be drying.
- Pure coconut oil soaps are great for general cleaning and for laundry. That’s why I made my homemade laundry soap only with coconut oil.
- Pure olive oil soaps tend to be gentle on the skin and great for gentle body cleansing.
Read my post about the properties of different oils in soaps.
Ideally, you’d combine different oils to get the qualities you want for your soap. 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 which uses a combination of olive oil and coconut oil.
Combining liquid soaps
When you make a bar of soap, you have to decide what combination of oils 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. Once you’ve made both of them, you can combine them, as needed to get the type of soap you want.
Coconut oil liquid soap vs. liquid Castile soap
When I first started making liquid soap, I assumed that liquid soaps would be just like bar soaps. The difference between a pure Castile bar soap and a coconut oil-based bar soap is HUGE!
I was very surprised to find, though, that liquid soap made with coconut oil was actually quite similar to that made with olive oil. Sure, the olive oil-based liquid soap was darker in color than the coconut oil-based liquid soap. For me, that was probably the most notable difference.
Yes, the coconut oil soap does make a bubblier lather than this one and may be slightly more drying. It does give more of a “squeaky clean” feeling.
In the end, though, the difference isn’t as pronounced as I expected. In fact, I normally just make the coconut oil liquid soap recipe these days. I can buy refined coconut oil cheaper than olive oil, but also love the look of a lighter-colored soap. I also love the fresh, subtle scent of the coconut oil soap when left unscented.
Both soaps give a decent lather. They are also both relatively mild for skin. If you have sensitive skin, though, this soap is probably the better choice.
Those who have very sensitive skin may find that they have issues with the higher pH of any soap. In those cases, it may be best to use something like my DIY Baby Wash and Shampoo. (I made it pH balanced for a baby’s delicate skin.)
Ingredients
This soap uses 4 main ingredients: olive oil, potassium hydroxide, water, and glycerin.
You can use extra virgin olive oil or a lighter olive oil. What is important, though, is that you are using pure olive oil. (If it’s not pure olive oil, it may need a different amount of lye.)
For the water, it’s best to use distilled water. Tap water has minerals and may have other impurities that can affect the clarity of your soap.
Why use glycerin when making liquid soap?
One of the methods of making liquid soaps is called the glycerin method. It replaces part of the water with glycerin.
Adding glycerin moves the soap-making process along more quickly. Because I wanted to share a beginner liquid soap recipe, I chose the glycerin method to have this soap be as quick and fool-proof as possible.
Using glycerin may have some other benefits:
- 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 usually, in a couple of hours, I have a beautiful, clear liquid soap effortlessly.
- Glycerin is a humectant, meaning it draws moisture into the skin. I find that even my liquid coconut oil soap doesn’t feel drying, 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 my homemade glycerin bar soap has the same benefits.)
Materials
Procedure
Making a liquid Castile soap isn’t difficult and it can save you a lot of money.
To get the clearest soap we can, we’ll use a hot-process method. That means that we will be cooking the soap. During the cooking process, the saponification process will complete and our soap will be ready to use immediately afterwards. (Liquid soap doesn’t need a curing time in the same way as bar soap does.)
The easiest way to make this and have it come out perfectly is to use a slow cooker. If you don’t have access to a slow cooker, though, you can also try baking it in the oven. (I showed how I used this method in the post and video for the coconut oil liquid soap.)
Making the lye solution
Weigh out the glycerine, water, and potassium hydroxide (KOH).
Add the glycerin to the water and then carefully add the KOH to the water and glycerin mixture. (Not the other way around!) Make the lye solution in a well-ventilated area.
Stir the KOH into the water until it dissolves. It will be cloudy at first, but then it will clear up.
Making the soap paste
Measure out the olive oil and heat it over low heat directly in the slow cooker.
Slowly add in the the KOH mixture to the warm olive oil, and gently stir them together over low heat.
Once combined, use an immersion blender to blend the ingredients together in the slow cooker. In a few minutes the mixture will begin to thicken and look like mayonnaise. Soon after, it will look like a creamy pudding. (If you aren’t doing this over heat, it will take a bit longer.)
A few minutes later, the mixture will begin to look grainy and look like mashed potatoes or applesauce. Continue to blend.
If, at any point, the mixture becomes too thick to blend with the immersion blender, switch to mixing with a spatula or wooden spoon. It’s also a good idea to take breaks during the blending process so as not to burn out the blender.
As you continue to blend, it will start to get creamy again. It is now time to cover it and cook it for a while.
Cooking the soap paste
Cooking the soap paste will allow the soap to finish the saponification process and will also help achieve a perfectly clear liquid soap immediately. 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.
As you cook the mixture, it will begin to thicken up and become more translucent.
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 should continue to cook the soap in the slow cooker. 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.
Note: If you aren’t using distilled water, the soap paste may stay cloudy no matter how long you cook it! (For more reasons your soap paste may be cloudy, read my post about troubleshooting liquid soap problems.
How to dilute the soap paste
Once you have made your soap paste, you’ll need to dilute it to obtain a liquid Castile soap.
To dilute a soap paste you can:
- Let it dissolve by itself into water over the course of several hours (or overnight).
- Speed up the process by warming the water and soap paste over the stove or other heat source (like the slow cooker).
For clear soap, use distilled water. That will also help ensure the water is free of contaminants and the soap will keep as long as possible. By choosing distilled water, not only are you keeping the possibility of microbial contamination to a minimum, but you are also ensuring that minerals and other substances in your tap water won’t cloud your soap.
If you are making small batches that are going to be used relatively quickly (and aren’t concerned about clearness), you can probably get away with tap water without any issues. I still recommend using distilled water when possible.
Read more about how to dilute a soap paste here.
Customizing your liquid soap
How else can you personalize your soap?
Adding fragrances
Unlike with bar soap, you can add in additives like essential oils after the fact. So, you don’t have to divide your batch at trace and work quickly to make soaps with a variety of fragrances. Instead, you can make a large batch of concentrated liquid soap paste base. The soap paste can be stored away and keeps well for a very long time. (I’ve successfully stored soap pastes for several years without issues.)
You can then add in the essential oils or fragrance oils as you dilute the soap paste. This gives you the freedom, even months after making the soap, to play with fun combinations.
At the time of dilution, I mix the soap paste with distilled water and then I add essential oils to give my soap a personalized fragrance.
Does it need a preservative?
Whether or not liquid soap needs a preservative is a controversial subject. Personally, I don’t use one as the pH of soap is high enough that it’s not a favorable environment for the growth of most of the microbes that we’re trying to avoid.
If I were going to sell a liquid soap, though, I’d do proper microbial testing of the liquid soap to see if a preservative was needed or not. Most natural preservatives on the market aren’t effective at the high pH of soap anyway. (Euxyl® K 900 is an exception and would be a great preservative to consider for using in soap.)
For more liquid soap FAQ’s, read my post How to Make a Liquid Soap: Start Here.
Video
Easy DIY Liquid Castile Soap Recipe
Materials
Instructions
- Measure out the olive oil and add it to the slow cooker on low heat.
Make the lye solution
- Weigh out the glycerine, water, and potassium hydroxide (KOH).
- Mix the water and glycerin.
- Carefully add the KOH to the water and glycerin mixture. (Not the other way around!) Do this step in a well ventilated area.
- Stir the KOH into the water until it dissolves. It will be cloudy at first, but then it will clear up.
Make the soap paste
- Slowly add in the the KOH mixture to the warm olive oil, and gently stir them together in the slow cooker.
- Once they are mixed together well, use an immersion blender to blend the ingredients together. In a few minutes the mixture will begin to thicken and look like mayonnaise. It will later look like a creamy pudding.
- Shortly afterward, the mixture will begin to look grainy like mashed potatoes or applesauce. Continue to blend.
- As you continue to blend, it will start to get creamy again. Once you reach this point, you can stop blending with the hand held blender and can leave the soap paste cooking covered in the slow cooker.
Cook the soap paste
- As you cook the soap, it will continue to thicken and will become more translucent. To achieve a clear liquid soap we'll need to cook the soap paste for 3-4 hours. During that time, check on it and stir it up every half an hour or so.
Check for doneness
- To check for "doneness," we will look to see if the soap paste dissolves clear. To do this, take a small amount of the soap paste and dissolve it in distilled water. If the resulting soap is clear, the soap is finished cooking. If it's cloudy, continue to cook the soap paste for another half an hour before checking on it again.
Dilute the soap
- To make a liquid Castile soap, dissolve some of the paste in distilled water. I ususally use a ratio of one part soap paste to 2-3 parts distilled water. It can be left overnight to dissolve on its own, stirring ocassionally, as needed. You can also use heat to speed up the process.
Notes
- A slow cooker is perfect for this sort of job because it will gently warm without burning, and keeping things at a steady temperature. If you don’t have a slow cooker, you can bake the paste in an oven or cook it in a double boiler.
- Take breaks while blending so as not to burn out the motor of your immersion blender.
- If at any point the mixture becomes too thick to blend with the immersion blender, switch to mixing with a wooden spoon.
- If you’ve cooked for more than 3-4 hours and it still isn’t clear, there may be other issues. Tap water can give a cloudy soap. For other possibilities, check my post on troubleshooting liquid soaps.
- 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 the 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.
- Undissolved soap paste can be stored in glass or plastic containers in a cool dry place for more than a year. (I’ve had some for several years without problems.)
DIY liquid body soap recipe:
If you would like to combine this soap with a liquid coconut oil soap to obtain a bit more lather and a squeaky clean feeling, try using this ratio:
60-70% liquid Castile soap (made with only olive oil)
30-40% liquid coconut oil soap (for bubbly lather, link goes to the recipe post)
Essential oils of choice.
Mix all of the ingredients together, and keep a bottle in the shower to use instead of shower gel.
Add essential oils for fragrance. Lavender essential oil gives a lovely herbal scent. I also like citrus blends using lemon and bergamot.
What are your favorites?
This post was originally published on June 29, 2016. It was rewritten and republished in June of 2021, adding new information, more photos, and video.
Braeden
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?
Tracy Ariza, DDS
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.
Hadiza m shehu
Hi.
Pls can I cook the soap in rice cooker, instead of using crock pot?.
Thanks alot dear.
Tracy Ariza, DDS
Hello Hadiza,
I’m not really sure. It would depend on how low the temperature could be set for your particular rice cooker. Some people do bake the paste in the oven, though.
Perhaps I’ll try with my next batch so that I can share an alternative method for people without a slow cooker.
Lietzah Franssen
Thank you Tracy!!!
Another question:
How do you Store the Soap Paste?
~Lietzah
Lietzah Franssen
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
Tracy Ariza, DDS
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.
Lietzah Franssen
Thank you Tracy!!!
Another question:
How do you Store the Soap Paste?
~Lietzah
Anna
Hi Tracy,
I just stumbled upon your site yesterday and have been taking a lot of notes. My compliments for your easy and well explained instructions..they are so helpful! I haven’t yet made soap being a bit intimidated by the lye solution but I must, yes, must try.
Would the Liquid Castile Soap made only with olive oil be the best choice for a 10 month old with topical dermatitis ( we have tried so many different types and thought of making a very natural and gentle one)? I have a few other questions too… since I don’t have a crock pot I was looking to buy one. There are so many sizes, I was looking for the 3,5 litre or do I need a bigger one for the recipe doses ( there was a promo for a 6,5 litre one)? In the meantime can the soap be made in a double boiler? If so, what temperature would “low” be? I have heard that whatever utensils you use for soap making, even if well washed, cannot be used anymore in the kitchen, true? Last but not least, can you please put the link or at least let me know where you buy your inexpensive refined coconut oil? Living in Italy it might be easier for me to use your same source. Thank you ..
Tracy Ariza, DDS
Hi Anna,
Thank you!
1) As for soaps, liquid Castile soap is relatively gentle. Soaps made with olive oil are on the “conditioning” side vs. those made with coconut oil. I don’t notice that much of a difference in liquid soaps, though. The “problem” with soap, though, is it’s high pH. I actually formulated a baby wash and shampoo that is made with other surfactants instead.
2) My crock pot is 5.7 liters. I would thing that 3.5 liters is on the small side.
3) You could try making it in a double boiler, but it could be hard to do. I’ve heard of people baking their soap paste and want to try that method next time.
4) I do NOT use separate utensils for soap making and think that notion is silly. I think that started with the fear of lye- someone who didn’t realize that lye is used in food preparation all of the time. I have lye cured olives before. (Most do use lye to cure them.) It’s also used to make special crusts on some bagels and pretzels, etc. It’s not a toxic ingredient, but it is highly caustic because of it’s high pH so it can burn you just a like a strong acid could. As long as you are careful when you mix the lye solution, I see no other problems with lye. (I wrote a post about lye, if you’re interested. 😉 )
5) I’ve bought the refined coconut oil from several places now, depending on where I was ordering other ingredients from. (Check granvelada, jabonarium, and cremas-caseras.es.) They all sell it and you can get it in a variety of sizes, depending on how much you use.
Marie Morgan-Roth
I was wondering if anyone else had their soap separate?
Alex
Can you explain why you are working with an lye excess instead of a fat excess?
If olive oil has a saponification value of 0.19 you would only need 172g of KOH.
So if you want a superfatted soap you’ll need even less KOH.
Can you explain why you did it this way?
What lye excess is still acceptable?
Tracy Ariza, DDS
Hi Alex,
I calculated the recipe to be exact (per SMB crafters lye calculator, which is said to be the best for liquid soaps) rather than to have a lye excess nor fat excess.
I do superfat my bar soaps, but not my liquid soaps.
Most people make liquid soaps with a lye excess to ensure they are transparent. They then “neutralize” the soap later. I haven’t found that necessary if you make the soap exact enough. Then, you don’t need to go through the hassle of neutralizing.
You could likely get away with superfatting up to 1%, but much more than that, and you’ll end up with a cloudy soap. If that’s not an issue for you, feel free to try it. Just don’t be alarmed if your soap isn’t transparent.
I talk a little bit more about the pH of the soap, and when too much or too little lye is used in the post I linked to about neutralizing liquid soaps.
I hope that makes sense and helps. 😉
Susan Beks
In the absence of a hand blender what can I use?
Tracy Ariza, DDS
I’ve heard of people using either hand mixers or mixing by hand. (By hand is supposed to take forever, though.) Honestly, if you’re serious about making soap, I’d buy a cheap immersion blender. They’re pretty cheap normally.
Cat
Hi there,
I made the coconut oil soap and it came out fine but I didn’t realize you were using weighted oz and not FL oz for the liquid. I’m on my second attempt at this recipe so already cost committed. Since I used fl oz for everything, is there any way to salvage it? I mixed in on low/off in the slow cooker for 20 min and it wouldn’t set up. Ideas? I hate to waste another batch. Thanks.
Tracy Ariza, DDS
Hi Cat,
The only way I can think to try to save it in situations like this is to calculate the weight of what you did add, and then compare it to what the recipe said. You could then add whatever is needed of the ingredient that was lacking. (If it didn’t set, I’d guess you need to add more lye.)
Patrice Hill
Hi,
I have used this recipe for about a year now and I love it. My question is can I use this same recipe without the glycerin? Would I have to change anything? I tried to use a soap calc but it didn’t give an option for the glycerin. Their outcome was similar but they said it had no cleansing but very conditioning is this true? I’ve tried the exact recipe without glycerin and just like you said the glycerin does make the process easier, I noticed it took longer to get to a trace and the other stages without it. Since I made the soap without glycerin will it be safe to use on the skin?
Tracy Ariza, DDS
Hi Patrice,
Yes, you can make it by subbing the glycerin for water. As you said, it will take longer. I’m not sure about the differences for the skin. I’ve always made it with glycerin.
I usually use SBM crafters advanced lye calculator for liquid soaps. It does allow foe the addition of glycerin. (I wrote more about that in my post about lye calculators.)
Kathy
Hi Tracy,
I just made my first batch of liquid olive oil soap using the recipe above. I misunderstood the directions. I measured out 32 oz of olive oil (4 cups) and 8 oz of glycerin (1 cup) and 11.55 oz of distilled water (about (1 1/2 cups) thenI weighed out 6.52 oz of KOH.
I followed the directions and achieved each stage that you listed. I used a crockpot and it took about 4 hours.
I cooked it to a putty like paste and when added to distilled water it is pretty clear. I have tried it as a hand cleaner and it doesn’t appear to be irritating.
My concern is that I don’t know if it is safe overall? I do not know enough about KOH and worry that I used too much since I weighed the KOH and used liquid measures for the other ingredients. . I would like to share some of my paste with family if it is safe to use.
Could you please advise?. Thank-you I have enjoyed following your blog and I am excited that my soap looks like yours.
Tracy Ariza, DDS
Hi Kathy,
Well, I have to admit that I generally think that if it doesn’t irritate the skin (when it comes to soap recipes), then it probably is generally safe.
That said, I started to look up what the differences may be. For olive oil, I found that 32 US liquid ounces of extra virgin olive oil would weight 30.56 ounces at 76ºF. (Interestingly, it goes slightly up if you change the temp to 72ºF.)
8 fluid ounces of glycerine weighs 10.5 ounces. The water doesn’t matter.
Anyway, I guess you used a bit more glycerin- not a big deal either way, but slightly less olive oil than you should. So, the final pH maybe higher than normal and, yes, you probably have more lye than needed. It’s not uncommon to make liquid soaps with a lye excess, though- to ensure they are clear.
I’d suggest reading my post on neutralizing a liquid soap. That should help you determine how and if you should try to slightly lower the pH.
If you’re going to use it for cleaning, don’t worry at all about it! If you’re using for skin, then, well, it’s up to you. 😉
Tracy Ariza, DDS
I’d like to add that the extra glycerin doesn’t really matter either- but it may make your soap less irritating. (Some people make without glycerine and some people only use glycerin and no water.)
Sara
Hi Tracy,
I have been making Castille soap and my skin does feel clean and soft.
However, a white residue seems to be left on my skin.
I can literally scrape residue off my skin after using.
Please can you advise me how to get round this? Do I need to dilute with more water?
Many thanks in advance and have a good evening
Tracy Ariza, DDS
Hi Sara,
That’s interesting. I don’t have that issue.
Did you use this recipe?
Kathy
Hi Tracy,
Thanks for your advice. I am much more comfortable using my soap. I have added a lemon essential oil as a fragrance and it is very pleasant. I will soon be trying it as a cleaner.
You make it fun and easy to try new recipes. I look forward to trying another very soon and will follow directions:)
Thanks for sharing your knowledge and expertise.
Kathy
Tracy Ariza, DDS
I’m happy to hear it! Thank you! ?