Easy, Beginner DIY Liquid Castile Soap Recipe
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
To make liquid Castile soap, you only need a few basic tools. An immersion blender helps mix the oils and lye solution quickly so the soap reaches trace faster. A slow cooker works beautifully for keeping the soap at a steady, gentle heat while it cooks. A kitchen scale is also important here, since soap making relies on accuracy. Measuring by weight instead of volume helps ensure that your recipe turns out perfectly every time.
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 liquid castile soap (made from scratch with olive oil)
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.
- The mixture will go through stages, from creamy to grainy and back to smooth.
- 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. Let it sit until dissolved, or gently heat to speed it up.
Notes
- A slow cooker is perfect for this because it gently heats without burning and keeps everything at a steady temperature. If you don’t have a slow cooker, you can bake the paste in the oven or cook it in a double boiler.
- Take breaks while blending so you don’t burn out the motor of your immersion blender. If your blender gets too hot, you can pause and let it cook before continuing.
- If the mixture becomes too thick to blend at any point, switch to mixing with a wooden spoon.
- If you’ve cooked it for more than 3–4 hours and it still isn’t clear, there may be other issues. Tap water can cause cloudiness. For other possibilities, see my post on troubleshooting liquid soaps.
- This recipe makes about 4.5–5 pounds of soap paste, which can be diluted to 10–20 pounds of liquid soap or more, depending on how concentrated you want it. That’s roughly 1–2 gallons or more.
- Keep in mind that liquid soap is not as thick as commercial gels or surfactants. It has a thinner consistency and doesn’t need to be thick to be concentrated and work well.
- Undiluted soap paste can be stored in glass or plastic containers in a cool, dry place for more than a year. I’ve had some last for several years without any problems. It may eventually develop a slightly rancid smell, but can still be used for general cleaning.
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.
I am ordering supplies to make this soap! How much essential oil should I add to this recipe?
Hi Chloe,
It really depends a lot on the essential oil you use and your preference for potency. I hear people saying that you should use around 1-2% of the recipe, but I don’t normally measure at home. I usually go by nose and just add until I think it smells good- and then add the tiniest bit more for good measure. EO scents tend to fade much more quickly than artificial scents, so it’s always good to add a little more than you need.
I will say that my soaps aren’t highly scented. Most soaps you buy (even those scented with only EO’s) have a much more potent scent, so they probably are using larger amounts than I do. (I’m probably using much less than 1%)
Certain oils have scents that last much longer. Lavender is one of those.
Other oils may be irritating to sensitive skin if you add them in high concentrations. It’s not usually so problematic with soap because it’s a rinse off product, but it’s always something to keep in mind.
PS And I definitely used caustic potash (KOH), not the other one …
Hello Tracy,
Can this liquid soap be considered safe to use as hair shampoo as long as the ph is lowered with citric acid?
Hi Joan,
Well, as you seem to know because of the statement about lowering the pH with citric acid, soap has a high pH. Most shampoos have a lower pH because they have determined that the best pH range for haircare products is in a lower pH range (3.5-5.5).
No matter how much citric acid you use, you’ll never be able to lower the pH of soap to get it into that range. In fact, I’ve heard it said that you can’t really get soap to be neutral (ph=7). Once you start to lower the pH of soap, it begins to fall apart and won’t be effective. (I wrote a little bit about it in my post about neutralizing liquid soaps, but I need to update that post as I know more about the subject now and think I can add a lot to the post. 😉 )
So, rather than trying to drastically lower the pH of the soap, you could use the soap and do a vinegar rinse to help neutralize the pH of your hair afterward.
I don’t do well with soap in my hair, but, of course, not all people do well with all shampoos. I do know of people that use soap in their hair and that are quite happy witht he results.
Instead, I’ve been looking for safe alternatives.
I’m actually in the process of taking a natural haircare course, and have started to make my own natural shampoos. This week I think I finally found a few successful shampoos. (My husband likes the clarifying shampoo I made, and I’ve been using a cleansing conditioner type product.) They are non-soap surfactant based, but using mild surfactants and avoiding the other undesirables usually found in shampoos. If you’re interested, stick around as I’ll be posting some recipes here soon. (Not immediately, as I like to test out products for a while before posting to make sure we thoroughly approve of them.)
Sorry about my question I realized after I sent it that someone else had asked you and you answered. Sorry about that!! My mistake. Still, thanks so much for your kindness in going beyond and above to explain this to me. You’re absolutely right that if one tries to lower the ph of soap it stops being soap. Thank you for your blog I love it!! I have ancestors from Spain. They settled in Puerto Rico where I was born but now I live in the US mainlad. La Paella es mi plato favorito!! ?
You’re very welcome!
No worries- I will be doing posts on the subject soon enough. 😉
What part of Puerto Rico are you from?
I’ve been there several times and have seen quite a bit of it. I really loved it.
We also spent time on Culebra y Vieques. I loved the phosphorescent bays (dream like!), the El Yunque rainforest, the beautiful beaches, wonderful food. I totally wish I could find or grow quenepas here too. I don’t ever drink soda pop anymore, but if I had to choose one to drink, it would be Coco Rico. hahaha
Hi Tracy,
Thanks for the recipe. I tried it and succeeded on first attempt made me and my sons very happy. Later on as I learned further I added cetyl alcohol to small oil mixed and added it to my dilluted soap. Voila, I made my own conditioning shampoo. I added citric acid to it to lower the PH but it became less foamy. Is it normal? My next question is do I need to add preservatives to my new shampo since I also add water to it as we’ll as the aloevera gel. Thanks again Tracy.
Hi Lin,
I’m so happy it worked out for you!
I don’t have a lot of experience with using soap as a shampoo because my hair is very sensitive to the higher ph of soap and I’ve never been able to get it to work well for me. I haven’t tried adding cetyl alcohol to soaps, so that’s really cool that it worked well. I’ve been experimenting with mixtures of emulsifiers and different surfactants to try to make conditioning shampoos, and find it interesting to see what works and what doesn’t.
The problem with soap is that it really needs to be alkaline to be, well, soap. If you lower the pH too much, the soap will break down into its various components again. That could explain why you’re finding your shampoo to be less foamy when you lower the pH. That’s also why soap doesn’t work as a shampoo for many people (including me). I know of people who swear by using soap based shampoos, though. They usually have thicker hair that isn’t as bothered by the higher pH of the soaps.
I reached the translucent phase of the recipe and when I went back to check on it, it was hard! I turned the heat up (had it on ‘keep warm’) and it softened enough to break it apart. Will it soften back enough to stir? What did I do wrong and how do I fix it!?!
Hi Victoria,
Well, this comment arrived in the middle of the night for me, so you’ve probably already finished, but here are my thoughts.
I wouldn’t worry too much about it. Let it do its thing. For some reason, the way the process looks seems to differ from batch to batch, but in the end, you should end up with a decent soap paste.
If you can’t stir, just mash things up as best as you can to keep any parts from burning and to allow the center areas to be in closer contact to the heat of the pan.
Hello:-)
can i use this recipe for both hair and body for my baby?
Hi Rashmi,
If you normally use Castile soap for your hair and body, then, yes, you can use it for both. Soap in general has a high pH which makes it not-so-ideal as a shampoo for many people. It really depends upon your hair type. I don’t use soap for my hair because I don’t like the way it leaves my hair (but my hair is fine and curly). I think people with thicker hair can usually get away with it more.
Hello:-)
can i use this castile soap recipe for my 3months baby?
thanks in Advance
While, yes, you can use it on your baby, I suggest being conservative with how you use it, especially on babies and people with sensitive skin. Baby’s skin is quite sensitive, and I prefer using mostly just water on babies, saving the soap for dirty areas. (I actually think that’s a good practice for everybody and not just babies).
Each of us is different, though, and we all react differently to different soaps/surfactants. It’s always a good idea to keep an eye on how a certain product affects the skin and switch if need be. I use this soap on my son’s skin. He has atopic dermatitis and very sensitive skin, and I haven’t had any problems using it on him. That said, I reserve the soap for areas that are more prone to being dirty, or to actually remove a stain or something like that. Most of the time, he mostly showers with just water.
Hi there,
I was recently looking up ways to make DIY body oil wash as my skin is EXTREMELY dry and uncomfortable. I noticed most recipes called for “liquid castile soap” but I couldn’t find any that were just simply pure castille soap. They all had things like citric acid, palm oil, etc. in them. I want to avoid all of that, so I’d like to try your recipe on how to make your own. My question is, can I still use the other recipes I found, and just use this recipe to satisfy the requirement for the castile soap? I found a recipe I really like that includes honey, vitamin E oil, olive oil, and essential oils. Will adding all of these other ingredients in this recipe mess up the consistency? I noticed your own recipe at the bottom only includes the oil soap from your recipe and essential oils. Will adding vitamin E, olive oil, and honey mess things up for me? It’s my first time making this so I want to get it right! 🙂
Thanks in advance!!
Hi Kelsey!
You can definitely use this in the same way that you would use any other Castile soap.
That said, I’d like to caution you about some of the mixes that you can find online. Liquid soap doesn’t really normally need preservatives because it has a high pH. It’s basically self-preserving (just like honey).
The problem is that some of the recipes I’ve found actually make not-so-safe mixes because they either change the pH of the final product (which can both break down the soap itself and make it prone to bacterial contamination. Bacterial contamination can make your skin break out into a big red rash. (apart from other possible problems)) Honey can be problematic in homemade products because while it is self-preserving, once mixed with other ingredients, it actually makes a product more difficult to preserve. I wouldn’t suggest adding a lot, and would stick to very small batches so you don’t keep it around for very long. You’d probably want to test the pH of your final product too. If it falls below 9, you’d want to look into using some sort of preservative.
Adding more oil will make for a cloudy, less effective soap, but yes, it would probably be gentler. Adding a small amount of vitamin E can help keep the extra added oils from going rancid more quickly. ( I’d stick to around 0.1% of a recipe- and definitely not more than 1% as in higher percentages it can actually make them go rancid more quickly.)
Because it’s hard to know which recipes to trust, if I were you, I’d actually honestly start with just the plain Castile soap and see how you react to that. Some (maybe even most?) people with sensitive skin do really well with it. Others are affected by the high pH of soap. If you are one of the latter people, you may need to look into a surfactant based “gel” rather than soap. I took a course in working with natural surfactants, and I’m working on making those sorts of product for the blog soon!
I’d also recommend not using any cleaner all over every day. I like to use my emulsified sugar scrub on my arms and legs, and leave the soap and other surfactants for areas that are more likely to need deeper cleaning to avoid odors. 😉
hello tracy
and thanks for all the details, attention and care
i would like some help learning how to use the soap calculator.
in order to change the recipe a bit with more oils…
Hi Hilla,
I think we’ve already chatted over Facebook, but I’ll give a quick answer here too, just in case somebody else is interested in the answer.
For liquid soaps, I use the SMB crafter’s advanced lye calculator. It’s supposed to be the best for liquid soap recipes and has the advantage of allowing you to add glycerin to the recipe too. While glycerin isn’t mandatory, I’ve found that it makes the recipe go more quickly, making it easier for beginners especially. The glycerin also makes for a soap paste that is easily diluted, and a gentle soap.
I normally calculate my liquid soap recipes at zero% superfat so that I don’t have to worry with neutralizing the soap later on.
Agradezco tu valiosa información gracias por compartir
Gracias, Ale! 🙂