How to make liquid castile soap (uses potassium hydroxide lye)

Earlier this year I posted my recipe for making liquid soap from a bar of castile soap.  While I have been using that soap daily as a hand and dish soap and still like it, I have found it just does not compare to real liquid soap.  It works well for hand soap, but leave that soap residue and does not have the same cleaning power as my potassium hydroxide soap.  


Disclaimer: This post contains affiliate links, which means I may receive compensation if you make a purchase through these links.  There is no cost to you. See my Disclosure Policy for more information. 


I use Dr. Bronner’s unscented castile soap in several of my home made recipes, and it has been my safety net since I had an allergic reaction to a body soap a couple years ago (after a full body allergic reaction to a scented soap I was afraid of pretty much any chemical in my body products, so I exclusively used Dr. Bronner’s as a hand soap and body wash for a couple months).  Now that I have successfully made bar soap, convincing myself that I am capable of working with caustic chemicals without burning myself, I decided it was time to give liquid hand soap a try.  My goal was to make a liquid castile soap that I could use interchangeably with Dr. Bronner’s unscented liquid castile soap.   So far I have used my liquid castile soap as a hand soap, face soap, dish soap, in my dishwasher, and in my laundry detergent.  As far as I can tell this soap cleans everything as well as Dr. Bronner’s, when diluted in the same way that I dilute Dr. Bronner’s (for reference, my face and hand soap is a 1:3 ratio of soap to water, dish soap is a 1:1 ratio of soap to water, and I use just 1-2 teaspoons in my dish washing machine (combined with a pre-wash and vinegar rinse – I’ll post that recipe later)).

All soap is made with lye.  Soap is made by the chemical reaction called saponification, during which lye dissolved in water (or another water-based liquid) reacts with oils.  Bar soap uses lye called sodium hydroxide (which is used as a drain cleaner and can be found in hardware stores).  Liquid soap uses potassium hydroxide as the lye (it’s harder to find; I bought mine on Amazon).  

When I decided I wanted to make my own Dr. Bronner’s equivalent soap, I decided to peruse the internet to see if anyone else had success, before taking the time to experiment with multiple batches of my own.  I was in luck, finding an awesome recipe from Erica on Northwest Edible Life.  Since I had the same desire for an end product as Erica, and after reading her post a couple times, I decided my first attempt at this liquid soap would be using Erica’s recipe.  I double-checked the ratios of ingredients using soapcalc.net’s soap calculator and got the same ingredient amounts (for reference, this recipe is 3% superfat, oil ratio is 60% olive, 40% coconut, and water as a % of oils is 80%) 

Liquid Castile Soap
Yields 1
Liquid castile soap comparable to Dr. Bronner's unscented liquid castile soap
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9925 calories
0 g
0 g
1134 g
0 g
486 g
2041 g
14 g
0 g
0 g
603 g
Nutrition Facts
Serving Size
2041g
Yields
1
Amount Per Serving
Calories 9925
Calories from Fat 9925
% Daily Value *
Total Fat 1134g
1745%
Saturated Fat 486g
2432%
Trans Fat 0g
Polyunsaturated Fat 80g
Monounsaturated Fat 523g
Cholesterol 0mg
0%
Sodium 14mg
1%
Total Carbohydrates 0g
0%
Dietary Fiber 0g
0%
Sugars 0g
Protein 0g
Vitamin A
0%
Vitamin C
0%
Calcium
3%
Iron
22%
* Percent Daily Values are based on a 2,000 calorie diet. Your Daily Values may be higher or lower depending on your calorie needs.
Ingredients
  1. 907.2 grams distilled water
  2. 265.0 grams potassium hydroxide 90%
  3. 680.4 grams olive oil
  4. 453.6 grams coconut oil
Tools
  1. Immersion blender
  2. heavy silicone spatula or wooden spoon
  3. large crock pot - at least 6 Qt, larger is better
Instructions
  1. 1. Measure the oils and pour into the crock pot. Turn the crock pot on high.
  2. 2. Measure the water (use room temperature or cooler) into your large mixing bowl and place in a deep sink.
  3. 3. Put on safety glasses, rubber gloves, and long sleeves/long pants and closed toed shoes to protect yourself from the lye. Carefully measure the potassium hydroxide, and slowly pour into the water. Stir gently so all of the potassium hydroxide dissolves. Note that this reaction is exothermic - it will produce heat - and the fumes are toxic. Do not breathe over the bowl and stand away as you stir.
  4. 4. Carefully pour the water-lye solution into the crock pot. Using an immersion blender, blend for 3-5 minutes, until the mixture is uniformly opaque.
  5. 5. Every 30 minutes or so, for the next 3 hours, blend the mixture to help thicken. If your mixture is too thick to use the immersion blender after your 30 or 60 minute check, turn the temperature to low (or warm if you're already on low). My crock pot is extremely hot, and it frothed a lot, the volume increased to fill the crock pot, and when I stirred I noticed that it began to gel in less than 1 hour.
  6. 6. Once the mixture is too thick to immersion blend, use your spatula to fold the mixture over itself. Keep folding every 30-60 minutes for 2-4 hours (or longer if needed), until the entire mixture is a uniform, translucent gelatinous mass.
  7. 7. Dilution. Once you have a saponified, gelatinous glob of soap, you need to dilute it to use it. Lower the crock pot temperature to warm. Add 6-10 cups of distilled water to your crock pot (ultimately you need 10 cups, but my crock pot only had space for 8), and gently stir/mash the soap into the water. If you're able, stir/mash every hour or so until the glob is fully dissolved. This should take 4-8 hours if you're stirring frequently. You may turn off the crock pot and let sit at room temperature overnight. Stir well in the morning and heat on warm if needed to finish dissolving.
  8. 8. Turn off the crock pot and allow the soap to cool to room temperature. Strain if desired, and pour into a clean 1 gallon vessel (I used my now empty distilled water bottle). If you have less than 1 gallon, add more water to fill the gallon bottle and gently swirl to uniformly mix the water and soap.
  9. 9. Use your castile soap as you would Dr. Bronners!
Notes
  1. 1. All measurements are by weight, not volume. This is required to ensure complete saponification. If your measurements are not precise you may end up with unsaponified lye, which can burn!
  2. 2. Use only sturdy glass, ceramic, or stainless steel containers, and heavy duty silicone or wood spoons (I prefer silicone). NEVER allow anything with lye to contact aluminum.
beta
calories
9925
fat
1134g
protein
0g
carbs
0g
more
https://mygreenerliving.com/
This recipe makes 1 gallon (128 fluid ounces or 3.785 liters) of liquid soap.

Ingredients

907.2 grams distilled water

265.0 grams potassium hydroxide 90%

680.4 grams olive oil

453.6 grams coconut oil

Tools

Immersion blender

heavy silicone spatula or wooden spoon

large crock pot – at least 6 Qt, larger is better

liquid castile soap
ingredients
Notes

1. All measurements are by weight, not volume.  This is required to ensure complete saponification.  If your measurements are not precise you may end up with unsaponified lye, which can burn!  If you don’t have a digital kitchen scale, I personally love and recommend this American Weigh Scales digital kitchen scale. 

2. Use only sturdy glass, ceramic, or stainless steel containers, and heavy duty silicone or wood spoons (I prefer silicone).  NEVER allow anything with lye to contact aluminum! (If you don’t believe me, watch this video of a potassium hydroxide-water solution or this video of a sodium-hydroxide-water solution dissolving aluminum foil)

Instructions
  1. Measure the oils and pour into the crock pot.  Turn the crock pot on high*. (*my crock pot runs very hot, so I went through this process using the low or warm settings.  If things are moving quickly you can reduce the heat.)
  2. Measure the water (use room temperature or cooler) into your large mixing bowl and place in a deep sink.
  3. Put on safety glasses, rubber gloves, and long sleeves/long pants and closed toed shoes to protect yourself from the lye.  Carefully measure the potassium hydroxide, and slowly pour into the water.  Stir gently so all of the potassium hydroxide dissolves.  Note that this reaction is exothermic – it will produce heat – and the fumes are toxic.  Do not breathe over the bowl and stand away as you stir. 

    liquid castile soap
    water with lye dissolving
  4. Carefully pour the water-lye solution into the crock pot.  Using an immersion blender, blend for 3-5 minutes, until the mixture is uniformly opaque.  

    liquid castile soap
    oils water and lye after blending
  5. Every 30 minutes or so, for the next 3 hours, blend the mixture to help thicken.  If your mixture is too thick to use the immersion blender after your 30 or 60 minute check, turn the temperature to low (or warm if you’re already on low).  My crock pot is extremely hot, and it frothed a lot, the volume increased to fill the crock pot, and when I stirred I noticed that it began to gel in less than 1 hour.
    liquid castile soap
    45 minutes after adding lye to oils. Thick and almost expanding out of the crock pot: a sign my crock pot was too hot.

    liquid castile soap
    Significant volume decrease after stirring. Only minutes after the last picture was taken,
  6. Once the mixture is too thick to immersion blend, use your spatula to fold the mixture over itself.  Keep folding every 30-60 minutes for 2-4 hours (or longer if needed), until the entire mixture is a uniform, translucent gelatinous mass.  

    liquid castile soap
    1, 2.5, 4.25, and 5 hours after mixing the lye and oils. My soap was sully saponified after 5.5 hours.
  7. Dilution.  Once you have a saponified, gelatinous glob of soap, you need to dilute it to use it.  Lower the crock pot temperature to warm.  Add 6-10 cups of distilled water to your crock pot (ultimately you need 10 cups, but my crock pot only had space for 8), and gently stir/mash the soap into the water.  If you’re able, stir/mash every hour or so until the glob is fully dissolved.  This should take 4-8 hours if you’re stirring frequently.  I let my soap sit overnight and stirred/mashed the remaining gelatinous blob in the morning.  Due to 8+ hours ignoring my soap, this process took about 14 hours. 

    liquid castile soap
    diluting the soap
  8. Turn off the crock pot and allow the soap to cool to room temperature.  Strain if desired, and pour into a clean 1 gallon vessel (I used my now empty distilled water bottle).  If you have less than 1 gallon, add more water to fill the gallon bottle and gently swirl to uniformly mix the water and soap.

    liquid castile soap
    finished soap ready to store
  9. Use your castile soap as you would Dr. Bronners!

    liquid castile soap
    finished product
Cost

Potassium hydroxide: $12.99 for 2 lb (907.2 grams).  (265g/907.2g)*$12.99=$3.70

Olive oil: $16 for 3L (2784 grams). (680.4g/2784g)*$16=$3.91

Coconut oil:  $14 for 54 fluid ounces (1530.87 grams). (453.6g/1530.87g)*$14=$4.15

Distilled water: $1 for 1 gallon (3,785.41 grams). (907.2g/3785.41g)x$1=$0.24

Total: $3.70+$3.91+$4.15+$0.24=$12/gallon

Dr. Bronner’s unscented liquid castile soap is $18 for a 32 oz bottle.  That’s $4 more for 1/4 the volume!  

Liquid Castile Soap from Bar Soap

Disclaimer: This post contains affiliate links, which means I may receive compensation if you make a purchase through these links.  There is no cost to you. See my Disclosure Policy for more information. 

I’m going to be nice and give you the recipe right from the start 🙂

Update 12/1/2016: I now make my liquid soap using potassium hydroxide lye and am much happier with that product.  You can see how I make that improved liquid soap here.

Liquid Castile Soap from Bar Soap
How to make liquid castile soap from a bar of castile soap
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124 calories
0 g
0 g
14 g
0 g
1 g
2858 g
114 g
0 g
0 g
12 g
Nutrition Facts
Serving Size
2858g
Amount Per Serving
Calories 124
Calories from Fat 124
% Daily Value *
Total Fat 14g
22%
Saturated Fat 1g
5%
Trans Fat 0g
Polyunsaturated Fat 2g
Monounsaturated Fat 10g
Cholesterol 0mg
0%
Sodium 114mg
5%
Total Carbohydrates 0g
0%
Dietary Fiber 0g
0%
Sugars 0g
Protein 0g
Vitamin A
0%
Vitamin C
0%
Calcium
9%
Iron
0%
* Percent Daily Values are based on a 2,000 calorie diet. Your Daily Values may be higher or lower depending on your calorie needs.
Ingredients
  1. 1-4oz bar castile soap
  2. 1 tbsp glycerine
  3. 3/4 gallon (96 oz) water
  4. Optional, 1 tsp liquid vitamin E
  5. Optional, a few drops of essential oils
Instructions
  1. 1. Grate the bar soap. You can get a good arm workout in grating by hand with a cheese grater. Or you can chop up the soap into 4-8 pieces, toss in your blender and pulse until you have small crumbles. I used the blender.
  2. 2. Pour water into a large pot. Ensure there is at least 2-3 inches between the top of the water and top of the pot. Boil the water for one minute (See Note 1). Turn burner to low.
  3. 3. Allow the water to cool for a few minutes, then pour in the grated soap. Gently stir to dissolve the soap into the water. It should dissolve in a minute or two unless you had large chunks of soap. Those took about 5 minutes to dissolve. Turn off the burner.
  4. 4. Add the glycerine, vitamin E and essential oils if using. Stir to distribute.
  5. 5. Let sit several hours or overnight to cool. The soap will remain very watery, but still works like soap! Some of the soap may separate (cloudy at the bottom of the bottle), just give it a quick shake before using.
  6. 6. Pour into your soap dispenser and enjoy!
Notes
  1. Note (1): According to the Center for Disease Control, boiling water for 1 minute will make it safe to drink. While I think my tap water it pretty safe (I have been drinking it for 6 years), I boil the water to kill anything that may be living in it, so my soap doesn’t start growing things. If you use distilled water, you can turn off the heat as soon as the water comes to a boil.
beta
calories
124
fat
14g
protein
0g
carbs
0g
more
https://mygreenerliving.com/
Before I started my healthy/natural kick, I had another problem.  (Ok, I have a lot of problems.  We’ll just tackle one at a time…)  It seemed for every gift giving occasion, someone (or multiple someones) gave me some fancy bar soap.  Are they trying to tell me something?  Do I really smell that bad?  Self-doubts aside, my problem was that I don’t really like bar soap.  It’s too difficult to keep looking nice and clean next to a bathroom sink, and I don’t like how it feels like it’s leaving residue on my skin when I use bar soap in the shower.  I am definitely a liquid hand soap/body wash girl. 

Update 4 Jan 2017: I have learned that “real soap” – castile soap and the home made ones without chemicals do not leave that residue on my skin, the sink, the shower…and I now love bar soap.

So, what to do with all this bar soap?  Per my usual, I turned to the internet (specifically Pinterest, my weakness).  I found a recipe that involved grating up the bar soap and adding it to heated water until it dissolved.  I tried it.  Worked great!  I used this lovely almond scented soap as a hand soap in my bathrooms for a couple months.  Then one day I ran out of body wash.  Body wash is just glorified liquid soap, right?  So why not use this lovely smelling liquid hand soap?  BECAUSE YOU’RE ALLERGIC TO EVERYTHING, IDIOT!  Well, apparently I forgot about that at the time.  Or I thought because it was ok on my hands it would be ok everywhere.  But I was very wrong.  I got contact dermatitis all over my body (have you ever gotten poison ivy? Yup, it was that reaction).  It took over a week for the contact dermatitis to go away.  That was not fun, but at least I did this stupid experiment in the winter when it was easier to cover up.  

This lovely adventure in discovering a new allergy led me to determine that I needed to get rid of chemicals.  I could not handle being allergic to soap.  So I turned back to the trusty internet.  This time I was smarter, and looked for recipes for fragrance and chemical free soap.  And this is when I learned about  castile soap.  The liquid stuff looked great, but over $15 for 32 ounces?  That was not going to be affordable as an every day and and body soap.   (I did purchase Dr. Bronner’s unscented liquid castile soap for a face wash and I do really like it.)  I immediately went out and bought the first castile bar soap I could find. It was Kirk’s Original Coco Castile, which I found at Walmart.  

Kirk’s soap is vegetarian (actually vegan) and contains no artificial ingredients.  Ingredients: coconut soap, water, vegetable glycerin, coconut oil, natural fragrance.  According to the the FAQ’s page of Kirk’s website, the answer to “What kind of fragrance do you use in your soap?” is “The fragrance is less than 1% of the total ingredients in Kirk’s products. The fragrance is a combination of essential oils from the pine and citrus family and is Phthalate-Free. For those with highly sensitive skin we recommend our Kirk’s Original Coco Castile Fragrance Free Bar.” 

Since I have not had sensitivities to and of the listed ingredients, or pine or citrus, I guessed (correctly) that this soap would be safe.  It is so gentle that I can, and do, use it on my face.  

I use this soap as a hand soap, face soap, body wash, and any time my home made cleaning recipes call for liquid castile soap.

If you’re looking for a super-sensitive liquid soap that is less expensive than liquid castile soap, or just want an inexpensive liquid soap, here’s how to make your own!  

Recipe:

1-4oz bar castile soap

1 tbsp glycerine

3/4 gallon (96 oz) water 

Optional, 1 tsp liquid vitamin E

Optional, essential oils

Liquid_soap_1

Instructions:

1. Grate the bar soap. You can get a good arm workout in grating by hand with a cheese grater. Or you can chop up the soap into 4-8 pieces, toss in your blender and pulse until you have small crumbles. I used the blender.

Liquid_soap_3     Liquid_soap_5

2. Pour water into a large pot.  Ensure there is at least 2-3 inches between the top of the water and top of the pot.  Boil the water for one minute (See Note 1).  Turn burner to low heat.

Liquid_soap_6

3. Allow the water to cool for a few minutes, then pour in the grated soap. Gently stir to dissolve the soap into the water.  It should dissolve in a minute or two unless you had large chunks of soap.  Those took about 5 minutes to dissolve.  Turn off the stove. 

Liquid_soap_7

4. Add the glycerine, vitamin E and essential oils if using. Stir to distribute.

5. Let sit several hours or overnight to cool. The soap will remain very watery, but still works like soap!  I think it could even be watered down more and be just as effective – I’ll update as I experiment with this.  

6. Pour into your soap dispenser and enjoy!  If the soap appears to settle with time, just give it a quick flip/shake and it should be as good as new!

Liquid_soap_9

Note (1): According to the Center for Disease Control, boiling water for 1 minute will make it safe to drink.  While I think my tap water it pretty safe (I have been drinking it for 6 years), I boil the water to kill anything that may be living in it, so my soap doesn’t start growing things.  If you use distilled water, you can turn off the heat as soon as the water comes to a boil.

I chose not to add any essential oils due to my skin sensitivity. If you want scented soap, add just a couple drops at a time. You can always reheat soap in small batches and add oils to your smaller batch.

My first try, I used 1/2 gallon (64 ounces) water.  After the soap sat in a bottle for a month, it was too thick to pump out of a regular soap or lotion pump.  I’ve re-made this soap with more water, and I like it much better.

Odds are you have a hand soap pump bottle in your house.  I am all about reusing, so go ahead and keep using what you have!  Or, get creative: I have found that some lotion bottle pumps fit on glass beer bottles. The threads on the bottle and cap don’t align quite right so it will leak if turned on its side, but it fits well enough to use.  

Insider tip #1: Don’t go adding extras to your whole 1/2 gallon batch of soap. I decided to add that Aveeno Oatmeal bath stuff (which I bought to help with that fun contact dermatitis – works great for that application!). To my whole batch. Thought it would make it softer and soothing. All it does is separate and make my soap cloudy, and clog the pump.  And it took me over a year to go through a 96 ounce batch.

Insider tip #2:  As you’re making your soap, at step 3, you might think it is a good idea to use your hot water to dissolve the soap that is stuck in your blender.  If you chose to do this, please use extreme caution!  Because if you fill your blender ⅓ with water, and blend, the entire volume of your blender is instantly filled with beautiful white suds!  These suds are pressurized!  When you open the blender, warm soapy water will spray everywhere!  If the water is too hot, you could burn yourself, and I really don’t want that to happen.  If you insist on making a mess, please ensure that the water has cooled first.  

 

Cost breakdown:

Water: $0.0075 (My water rate is roughly $0.01/gallon, so cost here is 3/4 of one cent. I’ll round up to $0.01 for simplicity in this calculation. )

Kirk’s bar soap: $3.28 + 7% sales tax = $3.51 for 3 bars = $1.17

Vegetable glycerine: $2.99 for 4 oz bottle, ½ oz used in this recipe = $0.38

Total cost for 96 ounces: $1.56

I had been paying $3.97 + tax for 56 ounces of store brand hand soap 

Mine: 1.625¢/ounce

Theirs: 7.09¢/ounce

 

Where to buy ingredients:

Kirk’s bar soap can be found in a 3  pack in the soap aisle at Walmart ($3.28 for a 3 pack currently), or on Amazon

Glycerine can be purchased from a pharmacy.  It is not prescription, but behind the pharmacy counter.  I bought my NOW solutions vegetable glycerine on Amazon because I wanted to ensure it came from vegetable sources.  

Vitamin E capsules can be purchased at almost and drug store, grocery store, Walmart, Target, etc. in the vitamin aisle.  You can just pierce the gel capsule and squeeze the liquid into the soap.  Or purchase liquid Vitamin E on Amazon 

Essential oils can be purchased on Amazon (I like NOW brand), or from other companies like doTERRA and Young Living.  I have used doTERRA with success as well.  

Credits: I got the idea for making liquid soap from a bar from One Good Thing by Jillee