I really like making soap. My most recent soap creation is a homemade castile soap, made with olive oil and milk. The fluffy snow I see outside inspired me to make a light and gentle soap. When I use that first piece of soap from a new batch of all natural homemade soap, I get the same kinda satisfaction that my bug gets when she successfully puts a 4-piece puzzle together for the first time.
After working tirelessly to fit that initial 3 pieces together (with her tongue sticking out the whole time, because that’s how my 2-year-old concentrates), she looks at her last piece, looks at the 3 pieces that are on her little table, and looks at her last piece again. I think she’s saying to that final piece, “OK, we are gonna do this, now work with me, please.” She then gently wiggles the last piece into its place. And voila! She claps her hands, and all I see after that is pure joy and self-satisfaction.
That’s me when using my own handcrafted soap. I get that feeling of triumph and amazement every time, because I can’t believe I just made this awesome, all natural handcrafted soap! I made it through the simple process of mixing oil and lye! It’s so unbelievable.
The main ingredients for my newest creation, homemade castile soap, are olive oil and milk. Olive oil soap is renowned for its ability to clean without stripping the natural serum on your skin. Olive oil soap is moisturizing, hypoallergenic, and gentle enough for the most sensitive skin. Read more about olive oil soap here and here. Like olive oil soap, milk soap also does wonders for your skin. Milk soap is nourishing and gentle. Read more about milk soap here.
After looking into both olive oil soap and milk soap, I thought, why don’t I combine the awesome goodness of both soap into one homemade castile soap! At that moment, the picture of my bug kneading together two different colors of homemade play dough to form one even awesome-er play dough popped into my head.
Equipment Used to Make Homemade Castile Soap
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- Crock pot – this is a must, because this homemade castile soap recipe is a hot process soap recipe. This means that the soap needs to be cooked in a crock pot. Yep, that’s why they call it crock pot soap. I got my crock pot at a goodwill store for a few bucks.
- Digital scale – it will help you figure out how much oil, milk and lye to use to create your homemade castile soap. Amazon sells this one.
- Electric stick blender – I commandeered my husband’s stick blender when I first started to make homemade soap. Maybe you can do the same from one of your love ones. Or you can look for one in a goodwill store. I use the stick blender to encourage the oil and lye to mingle and become all natural soap quicker. Some people (not many) do the mixing by hand. Yes, you can do that, but it will take you a long time (maybe around 30 minutes?).
- Glass measuring cups – you need them to make your lye solution. I use Pyrex 3-Piece Glass Measuring Cup Set. You can tell I love them. They appear in many of my pictures. These glass measuring cups are durable and easy to clean.
- Silicone spatula – you will use a silicone spatula to mix your lye solution, and mix your oil with lye. Look for some in a goodwill store. Are you sensing a pattern?? You can save a ton of money by first visiting a goodwill store or a thrift store for your equipment.
- Safety gear – gloves, goggles, an apron, a long-sleeve shirt, long pants and closed-toe shoes. You need to take precautions when working with lye. If you have never worked with lye, be sure to read this article and this article to learn more. I also discussed lye safety in my previous soap making posts, such as this one and this one. It’s a good idea to have plenty of vinegar around so you can neutralize the lye, if necessary.
Homemade Castile Soap Using Olive Oil & Milk
Prep Time: 2 hours (including about 1 and 1/2 hours of cooking the homemade castile soap in a crock pot)
Yields: 12 1-inch thick bars of homemade castile soap
Ingredients for Homemade Castile Soap
- Olive Oil – 33.8 oz. I use Trader Joe’s Imported Olive Oil. You can try Kirkland Signature Organic Extra Virgin Olive Oil, or La Tourangelle Extra Virgin Olive Oil.
- Whole Milk – 1/2 cup. Get it at your local supermarket. UPDATE: one reader reported that adding 1/2 cup of milk caused the soap to separate. If you are concerned about this, use 1/4 cup, instead of 1/2 cup, of milk.
- Lye – 4 oz. I use Food Grade Sodium Hydroxide Lye. Yes, it’s kinda crazy, but you can use 100% lye drain opener (Roebic Laboratories Drain Cleaner Crystals), which you can get from Lowe’s Home Improvement Store. This lye is not food grade though. It’s hilarious, but most of the reviews for this drain opener are from soapers.
- Distilled Water – 9 oz. Get it at your local supermarket.
- (Optional) Stearic Acid (plant-based) – 2 tablespoons. I used this stearic acid. UPDATES: Since making this soap, I’ve decided to stop using palm oil and palm oil derivatives, including stearic acid. Read more about my decision here.
- (Optional) Lavender Essential Oil – 2 teaspoons. I use NOW Foods Lavender Essential Oil.
- (Optional) Clove Essential Oil – 1/2 teaspoon. I use NOW Foods Clove Essential Oil.
How to Make Homemade Castile Soap
1. Wear protective gear please. Make sure no little ones are running around or anywhere near where you are working with lye and making soap.
2. In a well-ventilated place, add lye into distilled water to make lye solution. Use a silicone spatula to mix the solution. Don’t breathe the fumes initially released when lye is added to water.
As the pictures below show, the lye solution will start up cloudy then become clear after about 10 minutes.
As I was making this homemade castile soap, a historic snow storm, Winter Storm Jonas, was raging outside. It dumped a ton of snow and burying everything in sight. See the snow accumulation by the door?? That’s just a tinsy winsy bit of the total accumulation.
3. Place Olive Oil into your crock pot. Turn your crock pot to medium or low heat.
4. Add Lye Solution into the Oil. Stir slowly with a silicone spatula. Make sure you are wearing all the protective gear – gloves, goggles, an apron, a long-sleeve shirt, long pants and closed-toe shoes. You don’t want any of the lye solution or lye and oil mixture to get on your skin. It’s caustic and it will burn. If you accidentally got some on you, wipe it with vinegar, which will neutralize the lye.
5. After hand mixing the lye solution and oil with a silicone spatula, use a stick blender to bring the mixture to a pudding consistency, also known as trace. It took me about 10 minutes. You will see that the mixture’s color turns much lighter, like the color of vanilla pudding.
6. Cover the soap and let it cook.
7. Check the soap every 15 minutes or so to make sure it isn’t bubbling over the crock pot. Below is what my soap looked like after cooking at medium heat for 45 minutes. It looked like soufflé rising up from a cup.
8. (Optional) The little white pieces you see in the picture are stearic acid. I added it to make the homemade castile soap harder and last longer. I used plant-based stearic acid. You can also use other types of stearic acid or not use any at all. I have made many batches of soap without it.
UPDATES: I no longer use palm oil and palm oil derivatives (stearic acid) in my products. I don’t want to contribute to the harms that palm oil production has caused to the environment, animal and people. Read more about my decision here.
9. (Optional) If you add stearic acid, then cover the crock pot again and continue to cook the soap for another 10 to 15 minutes, until the stearic acid is completely melted. See that puddle of liquid at the bottom of the picture? That’s melted stearic acid.
10. Mix soap and melted stearic acid. Continue to cook soap with the crock pot lid on until it reaches a Vaseline-like consistency. It took me about 10 additional minutes.
11. Add Whole Milk, and mix well.
12. (Optional) Add Essential Oil.
13. Once the milk is mixed into the soap well, scoop your soap into a mold. I use a wooden mold that my wonderful and crafty husband made for me.
I have also used silicone molds. If you use a bread loaf silicone mold, be sure to use it with a frame, because the silicone mold is not strong enough to hold the soap. People have also used yogurt containers, paper orange juice containers and shoe boxes with great success. All you need is a container that’s sturdy enough to keep the soap in its place. Don’t use anything made with aluminum though, lye doesn’t like aluminum.
14. Once the soap is in the mold, bang the mold against the floor or a hard surface a few times. You want to get the air bubbles out of the mold. This can get loud, because soap + mold are quite heavy.
15. Let your soap remain in its mold for at least 1 day. Or if you are patient, leave it in there for 2 to 3 days. You want to give the soap a chance to harden. I have found that it takes longer (at least 2 to 3 days) for the soap to harden in a silicone bread loaf mold.
16. Once your soap has hardened, remove it from the mold and cut it into bars. I cut mine about 1-inch thick. I usually let the soap cure/dry for an additional week before use. This ensures that there will be complete saponification, and there won’t be any lye left in the soap.
That’s it! You now know how to make homemade castile soap with olive oil and milk! I used a bar from this batch for the first time tonight, and was giggly with triumph. I used the soap while bathing my little bug, and I was completely happy with my creation. The soap was very gentle and moisturizing. The olive oil and milk were working their magic on my little one’s skin.
The homemade castile soap produced tiny, white, silky bubbles and its lavender scent smelled amazing. My little one loved it too and couldn’t stop playing with it and making little bubbles on her hands. She rubbed, rubbed and rubbed her hands together, saying: “Look, mama! Bubbles. Bubbles.” She’s at the age when she does everything she’s excited about 10 to 15 times. I happily looked at the tiny bubbles on her hands 10 to 15 times.
In addition to this homemade castile soap, I have about 6 or 7 other types of all natural handcrafted soap curing/drying in our spare room. I have posted a few of my all natural hot process soap recipes: Rebatch Soap / Hand Milled Soap, Olive Oil Crock Pot Soap and Olive Oil & Coconut Oil Crock Pot Soap. For all three recipes I use the hot process method of soap making, that’s because I’m impatient, and don’t like to wait a long time to enjoy my soap. I’m an instant gratification kinda girl. I have also tried the cold process method and the cold process oven process (CP/OP) method. But both of these methods require me to wait 1 month to use my soap.
I hope you will give this homemade castile soap recipe or my other of soap recipes a try. Be sure to share or pin the recipes if you like them. Reach out and share your experience. As always, I’d happy to answer any questions you might have. Happy soaping!!
I didn’t know much about soap making, But after reading the blog and the process of making soap, It looks pretty and natural and does not have any effects on the skin.
Could you use Oat or Almond milk?
Love this. Homemade soap is the best! I love getting all my ingredients from Bulk Apothecary because they give quality results every time.
I have powdered goats milk, powdered buttermilk, powdered whole milk, and powdered coconut milk. I’d like to try using powdered milk in this soap. Any tips or best practices to incorporate the powdered milk?
I have powdered goats milk, powdered buttermilk, and powdered coconut milk. I’d like to try using powdered milk in this soap. Any tips or best practices to incorporate the powdered milk?
Hi…
I can’t wait to try this recipe! I have a couple of questions before I do tho’…
1. Can I use salt to harden the bars and, if yes, how much should I use for this recipe..? Will it compromise the skin-loving benefits of the Olive Oil, Goat’s Milk and Essential Oils..? OR…is the salt not necessary if I cure the bars for a week..?
2. I am planning to use 2 tsp. of Lavender Ess. Oil and would also like to use ½ tsp. of Lemongrass Ess. Oil along with. I did not see the Lemongrass listed on your list of Essential Oils to use so, wanted to check first.
Do you have any online classes for soap making and cosmetics
Hello…I have your recipe a try today for the castile and milk (we used fresh goat milk) soap…we read where someone commented that their recipe separated after using 1/2 cup of milk…well, their right it does separate….we’ll be trying another batch using only 1/4 cup of milk…ours looks a lot like lumpy Apple sauce and the same color, is that a normal description for this soap….? We used our essential oils of choice and put it all in the wooden mold…covered with cardboard and a heavy towel..we followed the directions to the letter…ANY help you can offer would be greatly appreciated…
Why do you add the milk at the end rather than mixing it with the lye?
Great question! I usually use milk (frozen) to make lye solution when making cold process soap like this one. But in general, when making hot process soap, I add milk after the soap is fully cooked. That way the milk won’t get burned during the cooking process, and I can pour the cooked soap into a mold a bit easier. Hope you’ll give this recipe a try!
I wanted to learn how to make soap. My Mother did. You never have to throw your not perfect batch away. Put it on the stove on low heat. Keep a record of what changes you are making. If it won’t trace, then mix up some lye and water by reducing the amount of ingredients, have them about the same temperature and slowly stir them together. If you put in too much lye, your soap will separate and you will see tan water, which is your lye water. Add any kind of solid fat you have on hand and keep adding a small amount at a time. It will start to look like pudding, and you will have SOAP.
Great tips, Maggie! Thank you! 🙂
do you measere the water and oil by weight or by volume
I measure water, oil, and lye by weight (oz). That’s because online calculators that I use to figure out how much lye to use in recipes all use weight, not volume, for their calculations. I use volume to measure milk and essential oil (cup, tablespoon, teaspoon). Let me know if you have more questions. I’d be happy to answer them.
PLEASE do not use vinegar to “neutralize” lye. This a commonly repeated Myth in soap making. Plenty of fresh cool water is what is needed, especially if it’s on your face or in your eyes. You can actually make soap using vinegar as the liquid that you dissolve your lye in.
That’s a very good point. If the lye is on your skin (or in your eyes) many people use fresh water to wash the lye off. The theory is that if you use vinegar, it will have a reaction when neutralizing the lye, and become hot. For me, I use vinegar to clean up a lye spill that’s on the floor or on the kitchen counters. I wear goggles, long-sleeve clothing, and gloves to protect my eyes and skin. And if I do get lye on me, rinsing with water has worked well. Thank you for your tip!
Hello. Do u have to make sure the lye temperature and the oil temperature are the same before pouring them into the pot? And can u use 2% milk
Great questions. This is a hot process / crock pot soap, so you don’t have to worry too much about the temperature of the oil or the lye when you add them together. They will all be at a pretty high temperature during the cooking process. And yep, 2% milk works too. Your soap might not be as moisturizing as soap that uses whole milk though. The fat in the milk adds to the super fat content of the soap. Let me know if you have any more questions. Happy soaping!
just wondering, if I don’t use stearic acid will my soap be ok? will it be to soft? i’m a newbe t soap making????thanks!
Thank you for reaching out! Stearic acid does make a homemade bar super hard. Palm oil does the same thing. That’s why many soapers use stearic acid and palm oil. I don’t use stearic acid or palm oil any more. Instead, I now add salt to my lye solution.
When making my lye solution, before I add lye to the distilled water, I usually dissolve in the distilled water 1/2 tablespoon of salt for every pound of oil in my recipe. The salt hardens the soap. Also, I found that if I keep my homemade soap bar dry between uses, the soap bar can usually last around a month.
You might want to experiment and find what works for you. That’s the beauty of making your own soap. You can customize it to your personal preference! I’d love to know what you decide to do. Let me know if you have any other questions. Happy Soaping!
I will probably try making the soap without milk the first time since I haven’t make any before. Do I need to change the amount of water if I don’t use milk? Does it have to be whole milk? I only use 1%.
If I understand things right, you would not “cook” the milk with the soap, just mix it in with the soap? Wouldn’t that cut down on shelf life?? I’ve read a lot about cold process soap but this is new to me.
Instead of Stearic Acid I have learnt that you can use salt or Sodium lactate to make your CP soap harder. Would that work here as well, if so how much would I use?
Thank you for reaching out! You definitely can use water instead of milk for this recipe. You can use the same amount of water as you would milk. So after you finish cooking the soap, first add 1/4 cup of water. Stir the water into the cooked soap. If mixture is too thick to pour/scoop into a mold, then add another 1/4 cup of water. Instead of water, fat-free milk will work too.
I don’t like to cook the milk in the soap, because the milk (when cooked) will darken the soap. Milk used in the soap should not shorten the soap’s shelf life, because of the high PH level in soap bar. But to be on the safe side, it’s a good idea to use your milk soap within 6 to 9 months of creating it.
You’re right. You can use salt and sodium lactate to make your soap harder. If you use salt, add it to the water before you use the water to make lye solution. I’d add about 1/2 tablespoon of salt for every pound of oil. In this oatmeal honey soap recipe, I show in pictures how salt can be added when making soap. If you use sodium lactate, then add it to the lye solution after it’s cooled. I’d add about 1 teaspoon of sodium lactate for every pound of oil.
Hope you find the info. helpful. Let me know if you have any other questions. Happy soaping!!
Hello Margie …I tried the same recipe that you did today for the castile and milk (we used fresh goat milk) soap…we read where you commented that your recipe separated after using 1/2 cup of milk…well, you were, right it does separate….we’ll be trying another batch using only 1/4 cup of milk…ours looks a lot like lumpy Apple sauce and the same color, is that a normal description for this soap….? We used our essential oils of choice and put it all in the wooden mold…covered with cardboard and a heavy towel..we followed the directions to the letter…ANY help you can offer would be greatly appreciated…
I made this soap today and all went well until I added the milk and it separated!!!Please tell me what I did wrong
Thank you for reaching out! Oh, no. Sorry to hear that your soap separated. It must be so frustrating. Did you use any fragrance oil? That can cause separation. When did you add the milk? It should be added after the soap has been fully cooked, reaching a Vaseline-like consistency, which usually takes about an hour of cooking at low to medium heat. Assuming the separation happened when there’s no fragrance oil, and the milk was added after the soap is fully cooked, then I would continue to cook the soap/milk mixture. I haven’t encountered this issue, but I did some digging and found that hot process milk soap could separate easier than soap that has no milk. I Hope you haven’t thrown away your soap. I would do the following: stir the milk into the cooked soap, then keep cooking at low/medium heat in the crockpot. Check the soap every 10-15 minutes. It should eventually get back to a good consistency that you can pour/scoop into a mold. It’s hard to say how long this process might take. I’ve read it could take from 30 minutes to 2 hours. Be patient. With a bit of encouragement, your soap will (learn to) behave. Please let me know how it goes. Also, for your next batch, I would add less milk, 1/4 cup instead of 1/2 cup. Keep me posted please!
Nice to hear from you Silvia.I did throw the soap away and this morning I took it out of the bin again,It was all wrapped up in a plastic bag,hiehie,I don’t give up that easy.I cooked it again for an hour or more and let it sit for about 5 minutes and then addeda little water and lavender oil was to afraid to add milk again,It was very fluffy and light ,so will check it tonight.To come back to the separated soap.When the soap was ready and still simmering in the slow cooker,I added the milk and stir and it became a horrible mess,no essential oil added to the mix,Oh dear I was so disappointed,because the soap looked so good before adding the milk.I think I should have taken the pot off the heat and then added the milk,also my slow cooker might be too big.It is a 6.5 litre oval pot.Your pot looks smaller than mine,what is the size of yours?.My skin is super dry and I would love to do the olive oil and milk,,I also like to use a crock pot.So,yesterday after the mess I decided to make a new batch of the soap again ,but without the milk and this morning I had to cut a piece to test it.Oh boy,did I enjoy my shower,lovely soap,but no milk,I added some lavender oil though.I seriously think my pot is too big for this amount of soap,what do you think?.Thank you so much for your time.
Great to hear that you saved your soap! Hope it came out fine after some extra cooking and cooling down time. Homemade soap made with olive oil and milk is really wonderful. Hope your next batch will go more smoothly. Pure olive oil soap, like your second batch, is great too. I’m sure both soap will be wonderful for your dry skin. To answer your question, my crockpot is about 2.5 liter. I am not sure if the size of the crockpot makes much difference. I’ve made many small (like 1 pound) batches, and they came out fine.
Thanks for coming back Sylvia.I added the milk while it was still simmering,Think I must take it off the heat next time and then add the milk,Did not use essential oil.I threw it out and this morning I took it out of the bin again,all wrapped up in a plastic bag.hiehie,not going to give up.I cooked it for 80 minutes and it looked very funny and fluffy,took it off the heat and added a little water and lavender oil,will check tonight to see if it is ok.I think my slow cooker is way to big,its a 6.5litre oval pot;so the bottom is just covered,what is the size of your pot?I also made a batch of this soap but without the milk,came out beautiful!!!!Thank you so much for your time.
Please keep me posted about your soaping adventure! Hope the olive oil and milk soap behaved after some tough love, aka, additional cooking time. 🙂
I love, love, love this idea but I’m afraid of using LYE. Is there a natural replacement for it I can use instead? Do you have any other suggestion? Thanks.
All natural handcrafted soap made with olive oil and milk smells lovely and is super nice for the skin! If you want to make soap from scratch, you will need to work with lye. But if you absolutely don’t want to work with lye, you can make soap using the rebatch or hand milled method. You start with a few bars of all natural olive oil (castile) soap, such as Kirk’s Natural Castile Soap. You grate the soap, put it in a crock pot, add whole milk, and cook it until the milk is incorporated into the grated/melted soap (about 45 minutes). You then pour the melted soap into a mold. Wait a day to release your soap. You have just made olive oil & milk soap without using lye. Check out my rebatch/hand milled soap recipe. It should give you more tips on how to make soap without lye. Let me know how it goes or if you have any other questions!