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 sign-up to be notified about my next soap-making class here. No spam, I promise! Before we lather up, let me deal with a few FAQs…
Frequently Asked Questions
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.
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 alkaline. 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).
- Wear long sleeves to prevent any chemical burns if the mixture splashes.
- Wear safety gloves.
- Wear protective eyewear to protect your eyes from possible splashes.
- Do not touch, inhale or ingest potassium hydroxide. Store it far out of reach of children and pets.
- When you add potassium hydroxide to water (step 2 in recipe):
- Do it slowly.
- Always add potassium hydroxide to water, and never the other way around.
- Do this step outdoors away from children and pets.
- Do not inhale or let the lye fumes get into your eyes.
- Do not touch the lye solution.
- Do not leave the solution unattended, because it will look like water.
- Be careful when carrying the solution back indoors, because the bowl will be very hot. So wear oven mits to carry the hot bowl, if necessary. Be careful not to trip. Walk slowly.
- It is safe to bring the solution back indoors when it becomes clear, like water, and the fumes have dissipated.
- If your skin comes into contact with the lye or soap mixture:
- Don't panic.
- Immediately wash the area thoroughly with cold water.
- Then wipe the area with white vinegar to neutralize the lye.If you do touch it, you will first feel an itch, which then starts to feel like a burn. When you feel the itch, rinse with water, and then vinegar.
- Have white vinegar around at all times. It will neutralize the lye. Wipe counter tops or whatever the mixture touches with vinegar.
- Before washing your utensils with dish washing soap, first rinse them with water and then wipe with a cloth that is soaked in white vinegar, or rinse in a vinegar solution (just fill the sink with water and add about a cup of vinegar – rinse in there). Then wash with dish washing liquid as usual.
You can use the same pots and equipment to cook and to make soap, but you must ensure that you clean everything properly and that all your equipment is stainless steel. I personally don't have separate equipment for soap-making, and I use the same pots to make soap and soup. I do have a separate blender though. It is obviously ideal if you can afford to have separate equipment, but it's not absolutely necessary.
How you must wash all your equipment before cooking with it after soap-making:
- Rinse all your equipment thoroughly in cold water;
- Then rinse or wipe your equipment in a vinegar solution to neutralize any lye (eg. fill the sink halfway with water and add about 1-2 cups of vinegar, or wipe with a cloth that is soaked in white vinegar);
- Then you can wash your equipment with dish washing liquid as you would normally wash your dishes. Now your equipment is ready to use for cooking.
A special note about blenders: Some blenders are not completely sealed where the blade compartment is, and they allow food to get stuck behind the blade etc. If your blender is not properly sealed, DO NOT use the same blender for cooking and soap-making. You will get soap in your soup.
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?
Well, of course you can. The only reason to make your own soap is to save cost and customise, especially if you want organic soap (just make sure you use organic oils and additives). Just be cautious and always read the ingredients when you buy, as many retail soaps include unwanted and unnatural additives. This soap recipe only uses what is absolutely required to make soap, nothing added. All the rest is up to you.
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)
463g Distilled water (for the lye solution – see part 1, step 2)
230g Potassium Hydroxide (KOH)
900g* Coconut Oil
1 Litre Distilled water (for softening the soap paste – see part 2, step 2)
White vinegar for cleaning any spills.
*Note: When you buy one litre of coconut oil, you will get about 920 grams. That is why my recipe calls for 900g, because it is approximately what you will get out of a one litre tub. But always check the weight with a scale to be sure.
- Kitchen scale
- A heat-proof glass bowl (or ceramic) for the water. Check that the bowl is microwave and dishwasher safe.
- Large stainless steel pot for oils & water (minimum capacity: 2 litres)
- Good quality electric blender (cheap ones may burn out)
- Stainless steel spoon to mix
- Two litre jar or container to store your soap paste
- Bottles for your individual liquid soap products
- A cloth soaked in white vinegar for cleaning.
- Funnel (depending on the container you want to store your soap)
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.
- Make lye solution: Add 230g of potassium hydroxide (KOH) slowly to 463g of water in a heat-proof glass or ceramic 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. If you have a thermometer, the ideal temperature for the oil is 50°C. You should be able to touch the oil and not burn – not that I’m encouraging you to touch hot oil, this is just to give you an idea of what 50°C feels like. The oil is hot, but nowhere near boiling. 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, add the lye solution slowly to the warm oil (not the other way around), 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. The ideal temperature is 50°C. Do not touch the lye mixture to determine its temperature please – you will suffer a chemical burn. Rather touch the side of the glass bowl to determine that it’s warm, or use a thermometer.
- 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 with a two-prong mixer and only 5 minutes with an immersion blender (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, and cook the soap for 30 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 not stick to the pot. It will also become more translucent, but not transparent – kinda like cloudy vaseline. Cook this paste on the lowest heat for a minimum of 30 minutes (maximum one hour), stirring often. If this sounds like too much work for you, throw the mixture into your slow cooker and let it cook for 2 hours on the lowest heat.
- 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 (2 Hours or Overnight)
- 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 soap paste and distilled water: You have two options. You can soften the soap paste in the water over heat – so using a double boiler, slow-cooker, or in a pot (lowest heat), stirring every few minutes. This is quicker. Or you can add boiling, distilled water to the soap paste and just let it sit overnight in a sealed container. This requires less effort. When you wake up it should all be dissolved. If not, mix it with a fork breaking up the remaining bits, and let it stand a little longer. Here are some pictures of the phases that it goes through on the stove until completely dissolved into liquid soap:
Here is an image of the soap paste just sitting in a jar of distilled water overnight. It will dissolve completely by itself into liquid soap. This requires far less effort than the stove method shown above, and is my preferred method to dissolve soap paste.
- 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.
- 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 for 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 when it cools. If you are only using a small batch of soap paste at a time and storing the rest, you need less salt.
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:
Soap usually tests at pH 10, which is alkaline. 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. To do this, make a 30% citric acid solution (10g of citric acid in 30g of water, or 30g citric acid dissolved in 90g water). You shouldn’t need more than 20g of this solution for every litre of liquid soap. Add a little of the solution at a time to your liquid soap, mix it in well, and retest the pH. Repeat until you reach about pH 8. Less solution is better than using too much – so just use what you need to achieve a lower pH. Check the pH with your pH strips until you reach pH 8. This is not the best pH for skin and hair, but it is neutral which is better than alkaline. Our skin and hair is actually acidic testing between pH4.5 – pH 5.5. However, you will not be able to get the pH of soap down that low ‘naturally’, you will need additional chemicals. If you add too much of the citric acid solution, you will likely reverse the soap-making process and turn your soap back into oil. At a neutral pH however, your liquid soap will have a shorter shelf life of about 2 months and you will need a preservative to extend this shelf life. If you don’t neutralise the pH, your liquid soap will have a shelf life of 6 months since bacteria cannot readily grow in a pH 10 environment.
Recipe Variations & Substitutions
Unfortunately, you cannot substitute any oil for the coconut oil in this recipe, you must use coconut oil. The recipe needs to be recalculated for a different oil, because each oil requires a different amount of potassium hydroxide to saponify. 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, even though it is bubbly. You can thicken it with salt or xanthan gum (see part 3 above). Olive oil results in a thicker textured soap, but not as bubbly. Each oil has its own soap properties.
You can use this helpful online calculator to work out the exact quantities if you’d like to use different quantities, or different oils than this recipe, or if you’d like to experiment. The calculator inputs for my recipe are: 2:1 water to lye ratio, and a 0% super fat. You need at least a 1:1 water to lye ratio, but I like to have more water to make sure there is enough for all the KOH to dissolve. I have chosen a 0% superfat so that the soap paste can be used for household cleaning without leaving an oily residue. You can always add oils and glycerine to this liquid soap to make it moisturising for skin and hair products. 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).
Cost & Shelf Life
Cost Price: R15.63 per 250g of liquid soap.
Lasted me about: 3 months using the soap paste to make everything from hand soap, dishwashing liquid and shampoo.
Shelf life: The undiluted soap paste has a shelf life of about 2 years, whereas the liquid soap (after you’ve diluted the paste with water) has a shelf life of about 6 months if you used distilled water. This is why it is better to not dilute all the soap paste at once, but to rather store the paste and use it as you require more liquid soap. Scoop some paste out of its jar, and dilute it when you need some more liquid soap. If you neutralised the pH of the liquid soap, the shelf life is only 2 months and it will require a preservative if you want to store it for longer.
*Costs accurate at the time of writing, and based on best retail prices I’ve found.
- 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
- Customizable: You can completely customize this soap recipe. You can add any essential oils/ scents and other additives. This base can be used as a body wash, shampoo, dish washing soap and laundry soap etc.
- Less waste: 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.
- 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.