So you’ve conquered the soap bar, and now you’re ready to tackle making liquid soap from scratch. This post demonstrates how to make a basic liquid soap. I will try to explain this as simply as it really is, so that you don’t run away in a panic. It is a long process, but it is also an easy one.You can use this as a base to customise your own shampoo, dishwashing liquid, shower gel etc. I’ve included step-by-step photos that will hopefully make the process easier to follow.
If you are new to soap-making, I highly recommend trying my basic soap bar recipe first. The method for liquid soap is similar, so if you are familiar with soap bars then liquid soap will be a bubbly breeze. But if you haven’t, then liquid soap may sound complicated – which it is definitely not. If you’ve read other recipes, they may have intimidated you to the point of giving up. Yes, it is more involved than soap bars, but it’s still totally doable. If you are more of a practical learner, you can attend my soap-making classes. Sign-up to be notified about the next workshop here. No spam, I promise!
Before we lather up, let me deal with a few FAQs…
The biggest difference is the chemical used. Soap bars use caustic soda (sodium hydroxide/ NaOH), whereas liquid soap uses potassium hydroxide (KOH). This chemical allows the soap to become liquid without separating into layers. If you have tried the melting method whereby you grate, melt and dilute a soap bar to make liquid soap, then you will know what separation I am talking about. The second difference is that the process is divided into two parts - cooking the soap paste (similar to soap bars), and then making it into liquid soap.
I'm surprised at how many people think that the term "castile" is synonymous with "natural soap". They say they are looking for castile soap, but what they really mean is that they are looking for a natural soap. Castile is a particular kind of natural soap that is made using 100% olive oil in the recipe. All other natural soaps are just as good, except they use a different oil - like coconut oil, shea butter, sunflower oil etc. - so they cannot call themselves castile soap. Castile soap is named after the region in Spain where the olive-oil based soap originated. So now that you understand the difference, are you looking for an olive oil soap (castile) or just a natural soap?
Yes, potassium hydroxide (KOH) / lye is just like caustic soda, and it is dangerous. By itself, it should never come into contact with skin, eyes or your lungs! It is corrosive and very caustic. This is why you need to be extra careful when working with it in the soap making process. Unfortunately, it is absolutely necessary to make liquid soap. The reaction between lye and oil is what causes saponification (i.e. soap). Most importantly:
Once lye reacts with oil it results in glycerine and soap, which is natural and completely safe. So the reaction looks something like this:
Oil + Base (lye solution) -----> Glycerol + Salt (soap).
For those of you that don't know, "lye" is the term referred to when potassium hydroxide is mixed with water (it is a solution).
Liquid Soap Recipe: Step-by-step
Time: 1 hour to soap paste, 3 hours to liquid soap.
Yields: Approximately 2.5 litres (10 standard bottles of shampoo)
500g Distilled water (for lye solution – see part 1, step 2)
250g Potassium Hydroxide (KOH)
1 litre distilled water for softening the soap paste (see part 2, step 2)
White vinegar for cleaning any spills.
Note: I use 100% coconut oil for a cleansing and bubbly soap base. I customise this base to be more nourishing later by adding glycerine etc. However, coconut oil results in a water-thin liquid soap. You can thicken it with salt or xanthan gum (see part 3 below). Olive oil results in a thicker textured soap, but not as bubbly. Each oil has its own soap properties.
- A glass bowl for the water
- Large stainless steel pot for oils & water
- Good quality electric blender (cheap ones may burn out)
- Stainless steel spoon to mix
- Stainless steel knife to cut bars
- Two litre jar or container to store your soap paste
- Bottles for your individual liquid soap products (you can make these later)
- A cloth soaked in white vinegar for cleaning.
PART 1: Cooking liquid soap paste (1 Hour)
- Measure out your quantities exactly with a scale: This recipe is like chemistry. Unfortunately, there’s no compromise and you have to use a scale, and follow all instructions to a tee.
Note for those who want to customise the quantities: You can use this helpful online calculator to work out the exact quantities if you’d like to use different quantities than this recipe, or if you’d like to experiment. The calculator inputs for this recipe are: 2:1 water to lye ratio, and a 2% super fat. You need at least a 1:1 ratio, but I like to have a more water to make sure there is enough for all the KOH to dissolve. I don’t recommend using less than 500g of oils, because that can be too shallow to blend properly (unless you have a tiny, narrow pot).
- Make lye solution: Add KOH slowly to the water in a glass mixing bowl (NOT the other way around). Do this in a well-ventilated area. Outdoors away from any pets is best . Do not inhale any of the fumes from the reaction, do not touch the solution. The solution will be murky, it will become hot, and you may hear popping sounds – this is normal. This solution is known as lye.
- Start heating your oil: in a genuine stainless steel pot. Do not let it get to boiling point, this is way too hot. At this time, your lye solution is cooling down and the lye should start looking more clear (less murky) with time. Make sure that all the KOH crystals are dissolved by stirring with a stainless steel spoon.
- Combine oil and lye: Once both the oil and lye solution are roughly the same temperature, combine them slowly and start mixing with an electric mixer. Make sure the stove is on the lowest heat. You can check the temperature with a cooking thermometer (ideal temperature is 50°C), or you can do what I do and use your sense of touch. I determine this by seeing when both containers are warm to the touch (i.e. not so hot that I have to move my hand away immediately, but warm enough that I can touch the pot for a few seconds).
- Blend. First the mixture will look like it’s curdling (like image below). Keep going.
- Keep blending (+/- 20 minutes): Then your mixture will begin to look like apple sauce or thin porridge (image below). Keep going. It took me about 20 minutes to get to this stage (this is why you need a good blender)! The time this takes depends on the oil you use, and the speed of your electric beater. So don’t worry, it’s supposed to take a while.
- Keep blending (+/- 2 minutes): Eventually your mixture will become like soft and fluffy mashed potatoes. It took me a further 2 minutes to get to this point. Keep going.
- Keep blending (+/- 4 minutes): Then you will get to the thick and lumpy phase. It becomes like seriously stiff pap! Keep going.
- Mix by hand (+/- 15 minutes): It is at this point when your blender starts to struggle. So now is the time to switch to a spatula or spoon for manual mixing. The mixture will start to pull away from the edges and become pasty. It will also become more translucent, but not transparent – kinda like cloudy vaseline.
- Stop mixing…finally! When you reach this translucent stage, you can rest your poor arms. Your soap is cooked.
- Transfer your soap paste into a container for storage: You can keep this soap paste for months without it going off, which is better than storing ready-made liquid soap. Water invites bacteria – which needs a preservative. Now we move onto part 2, softening the paste into a liquid soap.
PART 2: SOFTENING PASTE TO liquid soap
- Measure out the soap paste you need: The dilution ratio is one part soap paste to one part distilled water (1:1). So if you want to make a cup of shampoo (250g), measure out soap paste that is half of your final quantity. I.e. 125g of soap paste if you want 250g of shampoo in the end.
- Measure out the distilled water: Measure out the exact same amount of distilled water as you did soap paste. If you want a thicker texture, use less water.
- Combine and soften your soap paste in the distilled water: You have two options. You can soften the soap paste in the water over heat – so a double boiler, slow-cooker, or in a pot (lowest heat), stirring every few minutes (quicker). Or you can add boiling, distilled water to the soap paste and just let it sit overnight in a sealed container (less effort). When you wake up it should be dissolved. If not, mix it with a fork breaking up the remaining bits, and let it stand a little longer. I did mine on the stove. Here are some pictures of the phases that it goes through until completely dissolved into liquid soap:
- Bottle it. When the soap paste is dissolved, you will have your final liquid soap! This consistency will remain and it will not separate or harden. This is the base for your liquid soap. If you used olive oil, you will now have liquid castile soap.
- Let it settle for a day (optional). It is safe to use your liquid soap immediately, but I like to let mine stand for a day just to settle. Then I add my additives like essential oils, nourishing oils etc.
There it is, you have made liquid soap from scratch. You can now customise this base by adding additives that suit your needs whether that be for household cleaning or skincare.
PART 3: Optional steps for soap nerds
These steps are completely optional and unnecessary, but cool if you like to go the extra mile.
- How to thicken the texture of your liquid soap with salt:
Before bottling your liquid soap, make a salt solution. Mix 15g (tablespoon) of salt in 40g of boiling water for every 450g of ready-made liquid soap. Once dissolved, add this solution to your already diluted soap. Your soap should thicken a bit, especially when it cools. If you are only using a small batch of soap paste at a time and storing the rest, you need less. Rule of thumb: For every cup (approx. 250g) of liquid soap, mix 8g of salt in 22g of water.
- How to neutralise the pH of your liquid soap:
If you are equipped with pH strips then you can go a step further and neutralise the pH of the soap to make it even more gentle on your skin (if it tests too basic). To do this, make a 30% borax solution (10g of borax in 30g of water, or 30g borax dissolved in 90g water). You shouldn’t need more than 20g of this solution for every 450g of soap paste. I suggest adding a little of the solution at a time, rather than the whole lot. Less is better than more – so just use what you need to achieve a neutral pH. Check the pH with your pH strip until you reach a neutral pH (the ideal for skin is pH7). You can also do this with citric acid if you do not have borax.
- The time that it takes to make. I think the end result and versatility is worth the effort. By making soap paste in bulk, you can dedicate one Saturday afternoon a year, which is manageable.
- Potassium hydroxide is not as readily available as caustic soda (for soap bars). You can find caustic soda in most hardwares, but need to buy KOH from a soap speciality store. (Buy online here).
CHERRY ON TOP
- You can completely customize this soap recipe. You can use any oil, and also add essential oils/ scents and other preferences according to your preferences.
- You can make natural soap in bulk for all your needs from household cleaning to body care, and save the cost and packaging waste of purchasing it all the time.
- It has many uses. This base can be used as a body wash, shampoo, dish washing soap and laundry soap etc.
- Eco-friendly and only contains what you need – there are no unnecessary chemical additives.
How was your liquid soap-making experience? Did you find my method easy-to-follow? I’d love to hear your feedback, so please share in the comments below.