I’ve been fascinated with soap making for a long time. What was once a common household skill now seems like such a complicated process that many people simply buy soap instead. Unfortunately, many conventional soaps have additives, antibacterial ingredients and artificial fragrances.
Slow Cooker Soap Tutorial
I first started using homemade soap when I realized that it was the most cost effective way to get an all-natural soap.
I buy all ingredients in bulk so for under $10 I can make 12-18 big bars of organic soap. Store-bought alternatives cost 4-5 times that amount.
A Word About Lye
Many people are afraid to try recipes that use Lye, but I’ve found that much of this fear is based on misinformation.
Yes, Lye (or Sodium Hydroxide) is extremely dangerous by itself. It can cause skin damage, blindness (with eye contact) and death (if ingested). Lye in its pure form is something that can be very harmful and extreme caution should be used when using it in any way.
Lye is created through the electrolysis of sodium chloride (salt) and it creates an extremely alkaline substance. If added to water, it becomes sodium and hydroxyl ions and creates a strong exothermic (heat creating) reaction. Flashbacks to high school chemistry anyone?
When Lye is used in soap making, it is what is called a reagent, meaning it is used in a chemical reaction to create other substances. In soap making, a carefully measured water/lye mixture is blended with natural oils in a process called saponification. Lye is simply an agent used to create soap from oils and water.
There is no unreacted Lye remaining in properly made soap. If you’re considering making soap, definitely use extreme caution with unreacted lye and use a soap calculator to make sure you are using the correct ratio of water/lye/oils but don’t be afraid of this age old process.
Where to Find Lye: Some hardware stores carry Lye (sodium hydroxide) though many have stopped carrying it. I wasn’t able to find it at any of our four local hardware stores so I ordered this one online. If you have a local (not big brand) hardware store they might also be able to special order it for you.
Hot Process vs. Cold Process
As the name suggests, the difference between these types of processing is if heat is used or not. With both methods, a water/lye mixture is used and oils are used. The two are mixed together in the process of saponification.
With cold processing, the water/lye mixture is mixed with the oil mixture and the resulting mixture is poured into insulated molds.
Hot processing adds an additional step of “cooking” the mixture which speeds the saponification process and makes the soap ready to use in days instead of weeks. Both methods work and I’ve done both, but the hot process method is much faster.
Choosing Ingredients for Soap Making
The advantage to making soap at home is that you can use high-quality organic ingredients and still get organic soap for much cheaper than store bought options.
In this basic recipe, I used organic Coconut Oil and organic Olive Oil, though any natural oils can be used. Use this Soap Calculator to figure out how much Lye and water are needed for whatever type of oils you want to use.
Really- the world is your oyster when it comes to picking ingredients but some popular and favorite ingredients are:
Once you’ve picked your ingredients, head over to the calculator and find out how much water and Lye you need.
For this specific recipe, I used an equal mix of olive oil and coconut oil, but just pure coconut oil can be used (like this great recipe from Mommypotamus) or just olive oil can be used. If just olive oil is used, you’ll have a pure castile soap (named after that region in Spain) which is very moisturizing but can take longer to cure.
I personally keep separate equipment to use for soap making. I found all of my equipment at a thrift store and keep it in the garage with the soap making ingredients.
Every source I’ve seen says that it is fine to use regular kitchen equipment for soap making as long as you wash it carefully afterward (see my notes at the bottom of this post on that). At the end of the process, you are just dealing with soap, so it isn’t toxic, but cleanup can be messy. To simplify, I just keep separate tools for soap making.
- A slow-cooker (I got an older one at a thrift store)
- A digital scale (this is important for making a soap that is not too harsh or too oily)
- Glass jars and bowls
- A stick blender
- plastic cups (optional)
- A metal spoon
- A wooden spoon
- A spatula
- Soap molds (or an old cardboard box lined with parchment paper). I have green flower molds, red silicon rose molds and basic bar soap molds.
- Gloves and sunglasses or eyewear
- A large bottle of white vinegar for neutralizing the lye mixture if it spills on anything.
Slow Cooker Soap Recipe
- 16 oz coconut oil
- 16 oz olive oil
- 4.844 oz lye
- 12.16 oz water
- 1 oz essential oils (optional)
- Prepare your mold. Wood molds will need to be lined with freezer paper or wax paper. Silicone molds are ready to use as is. You can also use any box if you line it with freezer paper, wax paper, or a thick garbage bag. I’ve heard of people using empty Pringles containers, but haven’t tried it.
- Make sure that your work area is clean, ventilated and that there are no children nearby. This is not a good recipe to let children help with since lye is caustic until mixed with water and oils.
- Weigh out 16 ounces of olive oil and 16 ounces of melted coconut oil and pour them both into the slow cooker.
- Turn on high just until the oils heat up and then reduce to low heat.
- While oils are heating, carefully measure the lye and water separately. TIP: This is the only thing I ever use disposable plastic cups for. They don’t weigh anything on the scale so they make measuring easy. I keep three separate cups labeled “Water”, “Lye”, and “Oil” to use for this purpose only. I reuse them each time so they aren’t wasted and I don’t worry about anyone drinking out of them since we don’t usually use these types of cups.
- Carefully take the cups with the measured water and lye outside or to a well ventilated area.
- Pour the water into a quart size or larger glass jar.
- With gloves and eye protection, slowly add the lye to the water. DO NOT ADD THE WATER TO THE LYE (this is really important).
- Stir carefully with a metal spoon, making sure not to let the liquid come in direct contact with your body.
- As you stir, the mixture will become white and cloudy and get really hot. Let this mixture sit for about 10 minutes to cool. It should become clear when it has cooled.
- When the oils in the slow cooker have heated to about 120-130°F, slowly stir in the water and lye mixture.
- Quickly rinse the container used for the water and lye mixture out in the sink. I rinse well and then re-rinse with white vinegar to make sure all the lye has been neutralized.
- Use a stick blender to blend the mixture in the slow cooker for about 4-5 minutes or until it is opaque and starting to thicken.
- Cover and keep the slow cooker heat on low to thicken. I set a timer for 15 minutes and check it every 15 minutes until it is ready. It will start to boil and bubble on the sides first. After about 35-55 minutes (depending on the slow cooker) it will be thick enough that the entire surface is bubbly and the sides have collapsed in.
- Turn the heat off and remove the inner bowl of the slow cooker.
- If you are going to use essential oils for scent, add them now. I added lavender and orange.
- Quickly and carefully spoon the mixture into the prepared molds.
- Cover the molds with parchment paper and set them in a cool, dry place.
- After 24 hours, pop the soap out of the molds. It can be used right away, but I prefer to let it set for a few more days so that it lasts longer.
As I mentioned, keeping separate tools for soap making simplifies the process since things don’t have to be cleaned enough for food use. I still clean all tools carefully with dishwashing soap and water and rinse with vinegar just to be sure.
Since we are making soap, I typically soak the crock from the slow cooker with all tools in it for 8+ hours to dissolve and use the soapy water to help clean all the tools.
Ever made soap? How did it go? Share your favorite recipe below in the comments!
Discussion (318 Comments)
I have been wanting to try my hand at making soap for ages now. With such an easy recipe I may just have no more excuses for putting it off! 🙂
What size molds do you use and how many soaps will this recipe make with that size? Love the idea and can’t wait to get started!
Yes, I too would like to know the amount of essential oil to put in at the end. Also, is this the same soap that can be used as a face wash soap for sensitive/acne prone skin? Thanks!!
Because homemade soap still includes the glycerin I’ve found it very gentle to the skin. It’s all I use even when bathing my children, and a nephew with acne prone skin prefers my homemade goat milk soap to any other facial cleanser.
I have absolutely loved everything you have created up to this…. What’s the point !!
Katie - Wellness Mama
Of making soap? It is less expensive and more natural than buying it.
What about liquid soap? I like using liquid in a pump bottle. Do you have a recipe for that? Is the lye what makes it bubbly/foamy?
Do the weights need to be that precise… 4.844 ounces? My scale only goes to 2 decimal places. Is it better to round up or down?
Katie - Wellness Mama
I think two decimal places is fine. Just round to two decimal places.
So this soap cleanses you like a store bought soap for showering? Approximately how many drops is an ounce of essential oil? Thank you thank you
Kelley Davis Mason
Yes, soap is soap, it all cleanses!! The difference between handmade soap and store-bought soap is that …for one you know what goes in it (and can use natural or exceptional ingredients)… And store-bought soap has been so altered, they remove the glycerin, have lots of non natural additives… Some can hardly be called soap anymore but rather “detergent bars”.
As for measuring out essential oils. Trying to determine drops per oz would be extremely tedious. Most essential oils that you buy in the health food store come in .5 ounces. So you would need two of those bottles to make an ounce. Just look at the weight on the bottle. Another way to figure it out is by measurement. Even though Soapmaking uses weights the liquid measurements for scent (don’t use liquid measurements for base oils) will get you close enough. 3 tsp in 1 Tablespoon. 2 Tbl are an ounce.
A rough estimate for measuring drops is 5 mL = 1 teaspoon, and 6 teaspoons = 1 ounce. If you have therapeutic grade essential oils, you might need less. I’m not sure what sort of EOs were used in the original recipe.
I’d love to make soap myself but I live in a small apartment in NYC with three very curious cats and using lye is not an option since I don’t have an “outside” if you will. I do purchase handmade soap from a farmer’s market and I have been holding on to the scraps. I have heard of rebatched soap. Do you have a recipe for that or any suggestions? I would appreciate any advice.Thanks!
Not sure if you ever got an answer to your question, but I save all my scraps from soap making and rebatch them once I have a large amount. I don’t know if different types of soaps can be rebatched together – you might want to do a google search to find results. You can just grate the soap using an old cheese grater/shredder (think yard sale or resale store if you don’t have an old one), put it in the crock pot on low, and add a very small amount of water to help it get going. Stir occasionally until all the lumps are melted and it looks kind of like thin mashed potatoes, and then spoon QUICKLY into whatever mold you want to use. I have used empty Pringles cans, works like a charm! After 10-12 hours, tear the can away from your soap and use a wire or a sharp knife to cut it. Leave the newly cut rounds in a dry, cool location for at least 2 days (I leave my rebatched soap sit for a week at minimum, just to allow it to fully set up and the excess moisture to leave the soap); otherwise, you will end up with very soft soap that disappears quickly. Keep in mind that you will probably have air bubbles in your set up soap, just because it will be lumpy when you mold it. But honestly, it doesn’t matter! Bubbles or no, it’s still a great way to get the most out of your expensive soap purchase (or to recycle left over pieces, in my case.)
I just made my first batch in my Brooklyn apt. I only have a slight window sill as out door space. I opened the window and put it there. I also put a fan on in the kitchen to make sure all air was moving out. I was quite nervous about the process, but it was fine! I’d just put the cats in the bathroom for the 30 minutes it takes to deal with the lye and clean up afterwards.
Can you use a regular pot, instead of a slow cooker. Haven’t seen them here in Norway.
Try Amazon, I got my slow cooker or crock pot from them. Never before heard of such a pot before here in Germany, but it was easily found there.
I’ve been making soap for years using a regular pot on the stove. Only recently have I heard of using a crock pot. Both use the same recipe & basic steps, but the crock pot seems to be much easier…less babysitting. 🙂 So check online for the steps on using a pot on the stove & have fun!
I make soap using a cast iron bean pot over an open fire. You really can use any heat source you want as long as you are paying attention and adjusting accordingly.
This is soooooo cool. I don’t know why I never thought about doing this lol but I appreciate how easy you have made it! Do you know if the company that you purchase your ingredients from is a cruelty-free company?