Hot Process Soap in a Crock Pot


A couple of years ago when I started making homemade soap, I was scared. Soap seemed so complicated. Once I started making it, I realized it was quite simple–and even easy. I wrote a post, How to Make Soap. While that post is still useful, especially for someone who has never made soap before, it includes a lot of information, for both cold and hot process. If you’re new to soapmaking, you need that base of knowledge, but the info overload does make it difficult to use the post while actually making soap. If you’re the type who likes to set your laptop open to a tutorial as you’re working through a new project, this post is for you–whether you’re a brand new soapmaker or you’ve made soap a time or two but still need the directions at hand.

This post contains simplified directions for hot process only. If you’re new to soapmaking, please absorb the more detailed information and instructions in How to Make Soap first then come back here to set your laptop open to this post as you make your soap.

If you’re ready to get down to the business end of your stick blender, let’s go!

This is my favorite soap recipe for a soft and nourishing bar with a light lather. The recipe below makes a two-pound batch, which is a good batch size for a beginner or when trying out a recipe, though I find a four-pound batch size is easier to work with when doing the cook. To make a four-pound batch, just double the recipe. (Likewise, if you prefer a one-pound test batch, cut it in half.) Be sure your crock pot is large enough for the size batch you’re making! Choose your own additives, fragrance, and coloring to make a unique soap.

If you want to use a different recipe, go ahead. You can use any soap recipe to make hot process soap. I’m providing this one here because I like it. You can find many recipes with exotic (and sometimes expensive and special order) fats and oils. I’m a farmer. I prefer easy-to-find, inexpensive, grocery store fats/oils that create a soft and cleansing bar.

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Crisco — 9.6 ounces or 272.155 grams
olive oil OR olive oil pomace — 9.6 ounces or 272.155 grams
lard — 6.4 ounces or 181.437 grams
coconut oil (76-degree melt point) — 6.4 ounces or 181.437 grams
distilled water — 12.16 ounces or 344.73 grams
lye — 4.463 ounces or 126.524 grams

CAUTION: Wear goggles and gloves any time you’re dealing with lye and while handling the soap until it tests non-caustic.

How to make Hot Process Soap:

Gather all tools, utensils, ingredients, and other supplies including your molds and prepare your work area. To make soap by the hot process method, you don’t need to take the temperature of your mixtures at any point. Just carry on the way your great-grandma did, except without the iron kettle and the open fire.

Step 1

Weigh each fat/oil.

Place fats/oils in a crock pot on Low.

Heat until completely melted. Turn the crock pot off.

Step 2

Put on your goggles and gloves. Weigh the lye–

–and the water (or milk).

ALWAYS ADD LYE TO WATER (or milk), not the other way around. I take the lye and water (or milk) outside to mix, releasing the fumes in the open air. Slowly pour the lye into the water (or milk). Stir with a slotted spoon and hang back so you don’t inhale the fumes. A water mixture will appear cloudy at first.

The mixture quickly clears. Take it back inside.

Step 3

Slowly pour the lye mixture into the melted fats/oils.

Stir briefly with a spoon then begin mixing with a stick blender.

Use the stick blender on and off so you don’t burn up your tool. This recipe takes me about 10 minutes to trace. (May take longer if using milk.)

Step 4

Identify trace.

When your mixture traces, it will be sort of like a soft pudding where you can draw a line in the mixture and see the “trace” you left behind.

Step 5

Set your crock pot to Low and put on the lid to start the cook.

The soap will gradually take on a waxy appearance. The edges will appear dryer than the middle as they push up the sides of the crock pot. Stir occasionally–this keeps the soap mixture cooking evenly. As it nears finishing, it will look like waxy mashed potatoes.

You can test it with a pH strip (usually takes several minutes to change color after dipping in the soap) or do the “zap” test with your tongue. My preferred and recommended method for testing is using a 1% phenolphthalein solution. When you think the soap is ready, take out a small dab and place on a paper plate. Put one drop of the solution on the soap. If it’s ready, it will remain clear. If it’s not finished yet, it will turn bright pink! Very easy and clear cut way to test soap.

The cook time of soap recipes will vary with the fats/oils involved. It takes about an hour for me with this recipe.

Once the soap tests clear, it’s no longer caustic and is safe to touch.

Step 6

This is optional, but I prefer to transfer the mixture to a new bowl and continue to stir for a couple of minutes, letting the soap cool slightly. This helps reduce the chance of a too-hot mixture “cooking out” your fragrance. In this case, I was making a two-layer soap (different additives, fragrances, and coloring) so I divided the soap.

Mix in the additives and colorant, if using, as you stir. There’s a fine line between letting the soap cool slightly and letting it begin to harden, so don’t over-do it. Add fragrance last. Additives and fragrance should be measured and prepared before the soap is ready to come out of the pot so that you can work quickly.

Additives: Use a maximum of 1/2 cup dry additives in a two-pound batch. (More may make your soap crumbly.) If adding honey, add 2 tablespoons per two-pound batch.

Coloring: I prefer liquid soap colorant. I find dry pigments are more difficult to blend evenly. Be sure you’re using soap colorant. Use as many drops as it takes to reach your desired effect. You can also color soap naturally in a variety of organic ways, and keep in mind that some additives (such as ground cinnamon) will color your soap.

Fragrance: Use no more than 1 to 1 1/2 ounces fragrance oil or essential oil per two pounds of soap. (More may make your soap oily.)

Scoop the mixture into the mold. Making two layers here, I placed the pink on the bottom and the yellow on top.

This is a “cherry-pawpaw” soap with cherry fragrance and red soap colorant (to turn it pink) on the bottom and banana-mango (“pawpaw”) fragrance and yellow soap colorant in the yellow layer, with the addition of dried ground banana (since I have no pawpaws yet) and the liquid from several Vitamin E capsules. (Vitamin E, aside from other benefits, is a preservative.)

When making hot process soap, by the time you put it in the mold(s), it’s soap. You may line the mold (I use freezer paper) to protect the mold (for example, a wood mold) from the oils in the soap and to make the soap come out easily. Unlike when making cold process soap, you’re not lining molds of various materials to protect from the reaction of the mixture prior to saponification. Hot process soap is already saponified by the time it goes into the mold. (See Pringles can note below.)

Bang the mold down a little to settle, cover the soap (I just fold over the freezer paper I used to line the mold), and clean up your work area.

As soon as the soap is cooled and hard–about 12 hours–it’s ready to remove from the mold, cut into bars, and use. I usually set the bars on end for a day or two while they continue to set.

Hot process is real soap, real fast!

Pictured with the “cherry pawpaw” soap is an apple-oatmeal soap–both made from the same base recipe above. In the apple-oatmeal, I used no coloring. Per two-pound batch, I added 1/4 cup ground oatmeal, 1/8 cup brown sugar, 1/8 cup white sugar, plus Vitamin E, and 1 ounce apple pie fragrance oil. The oatmeal and sugars make a lightly scrubby, conditioning bar combined at the same time with the soft and nourishing base recipe.

FYI, to make round bars, I use Pringles cans. No need to line them for hot process soap–eat the Pringles (get your kids involved, they’ll find it a real hardship), clean the can out, spoon the soap in, and just tear the can off when it’s ready to cut into bars.

See all my homemade soapmaking posts here.


  1. twiggityNDgoats says:

    Great post! I’m getting so excited about my class and then experimenting with making goat-milk soap. I guess I’ll have to clear off a shelf somewhere for soap-making supplies ๐Ÿ™‚

  2. babyberry says:

    I love making soap! Just a couple things I wanted to mention…You should never mix your lye/water in a glass container. Over time the lye etches the glass and it can shatter. It is always best to use a plastic container(I use a juice jug I bought at the $ store). Also, if you change from water to milk you should have to adjust the amount of lye. It isn’t bad if your soap is superfatted but It wouldn’t be good if it was lye heavy.

    Love your blog BTW!

    • Suzanne McMinn says:

      babyberry, I don’t like to use plastic because of the heat reaction. Re the milk, in hot process soap, you cook until it tests non-caustic, so you can use water or milk interchangeably. This post is specific to hot process soapmaking. One of the benefits of hot process is that the saponification process takes place right before your eyes. You never have to worry that your soap is not safe.

  3. CindyP says:

    Great post!

    The amount of milk in a 2# recipe is a little over 1/2 cup. The amount of fat in that 1/2 cup is minimal, so I wouldn’t even waste my time rethinking the lye amount. It would increase the superfat content to .01%. But then, I wouldn’t use a soap, unless it was a laundry or cleaning soap, with a 0% or less superfat…it’s just too harsh on the skin. Then I wouldn’t use milk in my laundry or cleaning soap either ๐Ÿ™‚

  4. bonita says:

    Wow. What a great tutorial. Made soap with my mom (no, not grandma) when I was a kid…nice to see process adapted to technology.

  5. gardnerh says:

    I love this tutorial. We’ve only made cold processed soap. Your advise about adding the lye to the water is really important. If you add the water to the lye, you create start out creating a really concentrated solution and , since this reaction is exothermic (creates heat), it can splatter or even explode. By mixing the lye into the water, the solution starts out dilute and becomes more concentrated. It still heats up, but not as abruptly. Especially if you combine the two slowly. One more thing of note with the lye – please tell me you’re wearing eye protection.

  6. gardnerh says:

    Oops! Just saw the goggle part – You think of everything :happyfeet:

  7. BunnyRuth says:

    Quick question … do you have dedicated equipment for soap making (i.e. the crockpot, immersion blender, etc.) or does it all clean off easily. Being soap I would htink it cleans off alright but just wanted to check. I continue to be a bit nervous about soap making, but am hoping to get over it by reading all your posts.
    Ruth in NH

  8. SanAntonioSue says:

    Thanks so much for the tutorial, Suzanne!! I’ve always wanted to make soap similar to how I remember my Mamaw cookin’ up in the back yard but have been too “skeered”. I’ve done the melt and pour before but, for me at least, its just not the same. Your tutorial makes it look very doable!! ๐Ÿ™‚ Hint: Try making yourself some peppermint/spearmint essential oil soap! Smells so refreshing and is very cooling on the skin in the hot weather, especially if the power keeps going out.

  9. Old WV Broad says:

    Thanks for sharing this Suzanne, you sure have whet my appetite for the retreat. Darn but that two tone soap looks good enough to eat!


  10. laurie hamar says:

    Suzanne, you got me hooked on making soap shortly after you made it the first time. I followed all of your directions (read through that original post many times before I started) and made the most beautiful soap in my pringles can. Since then my hubby made me a great wooden soap mold and I’ve taught my sister-in-law (who makes and sells her goat soap now) and my very good friend. I will always be thankful that I read that original post. Thank you.

  11. jamitysmom says:

    This is such a timely post! I have been collecting the materials to make my first batch of soap but that original post was a little intimidating (for me, anyway!). I am so happy to see the “condensed” version! For now I am only interested in the hot process soapmaking so this is perfect, thanks Suzanne! I just might do this today – it’s 90+ out there so I think making a batch of soap might be the perfect excuse to stay inside with the air-conditioning ๐Ÿ˜†

  12. fowlers says:

    Not wanting to sound silly::however I must (sigh), re: the stick blender, I have ordered my first today (yay me) going to try this weekend to make a very basic batch of Milk & Honey soap. Any who:: when you say “Use the stick blender on and off so you donโ€™t burn up your tool” could you please tell me what it is you mean? sorry but I’m clueless here: call it a blond moment or I was dropped once or twice on my head as a small child:: but regardless: I’m at a loss, was not sure if you were talking about the chemical reaction from the lye or the friction of the motor being on for to long? should I time it? rotate w/ a wooden spoon ?? Help a girl out pretty please::
    Oh and thank you so much for the pictures::finaly someone who appreciates pictures to help us gal’s out! trust me, I need all the help I can get sometimes:::lol you rock!

    • Suzanne McMinn says:

      Turning the stick blender on and off means just that–not running the stick blender constantly. If you ran a stick blender constantly for 10 minutes, you might burn up the motor of the stick blender. Turn it on and run it, then turn it off and just stir with it–then turn it on again etc. Give it a break every few minutes and just stir with it.

  13. fowlers says:

    Thank ya! I appreciate the information: I’m praying this adventure does not turn into a crazy mess: looking forward to starting it though!


  14. ibpallets (Sharon B.) says:

    Making Vanilla soap with chopped vanilla beans right now- What a great and easy recipe. Thanks Suzanne! Tomorrow….oh yeah, green peppers will keep me busy all day ๐Ÿ™‚

  15. ealisa says:

    I love your blog :] it got me started in soap making. I’ve been experimenting with different types of recipes, and am having problems with my layered soap like the one you did on this post. For some reason, the layers fall apart when I take them out of the molds. Do you know what could be causing this? Am I not pressing it into the mold hard enough maybe? Or waiting too long for it to set?

    Also, in a recipe I saw someone put dry unsweetened cocoa as a devider between layers. I believe this was for a cold process soap, do you think that would work for a hot process as well?

    Again, LOVE your blog :] Thank you!

  16. lovemypets00 says:

    :shimmy: Yay! I made soap! I can’t wait to make the next batch; hope to try the Vanilla Dreams or the Spa Soap recipe. Using the crock pot made this so easy. Thank you for the great blog!

  17. Jane L says:

    I am making this recipe right now and I am so excited! All is going well – except I can’t seem to make up my mind about mix-in’s at the end. I think I am going to go with nutmeg and wheatgerm. Possibly oatmeal/honey. Anyway, thanks for this great post and for all you do for us newbie soapers out there.

  18. soapisticated says:

    Suzanne, this is so awesome! Thank you so so so much for sharing. I’m loving this method of soap making! If you wouldn’t mind, I would like to use a link to your blog/this tutorial in my blog, . I am writing about my hot process soaping experience and would like to mention you for my inspiration! Let me know if that would be ok or not!

    Thanks again!!


  19. moximom1964 says:

    I love you soap tutorial awesome i am a soap making queen now…question can you use or have you used powdered milk? just wondering..i have a cow tho and 42 plus gallons a week we have a few extra to spare to make things like butter honey butter and now i want to try the milk how slushy? :snoopy:

  20. huskerdaisy says:

    I’ve never made soap but I’m really excited to try this process! I do, however, have one concern. I have parrots and birds are very sensitive to chemicals. Does the lye emit any fumes while cooking in the crock pot? Thanks in advance for your response!

  21. kansasa says:

    Thanks so much for the tutorial. I made your recipe for the 2nd time and was wondering about the measurements? You say it makes a 2lb batch and to double it for a 4lb batch, both times I made it I doubled it and it comes out to about 6.5lbs… I’m using your exact measurements so am I doing something wrong?

  22. thewifeandmom says:

    Hello! I came across your website today and I LOVE IT!! It answered so many questions I had, like if I can use any recipe with hot process. Very informative. I’ve been wanting to make soap for years now and after reading your site I think I’ll finally try it…the whole lye thing was an issue. I do have a few questions though…when making soap do you always use one liquid fat/oil and one solid fat/oil? Can they all be liquid or solid? Also, if I change water out for milk will that change the calculations for anything else? Should I use whole milk or does it not make a difference? Sorry so many questions but I just want to be sure I got it all before I try it! Thanks :wave:

    • Suzanne McMinn says:

      What kind of oils/fats you use can be changed to whatever you like, though remember that coconut oil adds good suds, so is good to include, but remember that any recipe should be put through a soap calculator. You can’t just substitute without running it through a soap calculator. You can substitute milk–usually it means a longer cook time.

  23. thewifeandmom says:

    Oh, one more thing…do you use KOH lye or NaOH lye? Does it make a difference?

  24. thewifeandmom says:

    I’ve checked out some different lye calculators before and it always says about “super fat” what in the world is that? Do you pay any mind to that?

  25. CindyP says:

    kansasa, the 2lb refers to the total amount of oil you begin with. the general rule of thumb is 1.6 times the total oil will be the end product.

    thewifeandmom, “super fat” is the amount of oil that isn’t “eaten” up by the lye. The higher percentage of super fat, the less amount of lye is used…same amount of oil, less lye. You can also super fat at the end of the cook by adding a percent or two of a nice oil. I generally run the recipe at 5-6% super fat, then if I want even more I will add a tablespoon of a nice oil after the cook.

  26. thewifeandmom says:

    Thank you, Cindy P. When you say “nice oil” what would that be really? After I posted that I read that 0% will make a very hard bar that doesn’t lather very well. We have hard water so I would def want to super fat so I can actually use it.

  27. MaidMirawyn says:

    Thank you so much! I didn’t use your recipe, but your tutorial was invaluable as my friend and I worked our way through our first soap. Your explanation was very thorough, without being overwhelming. I read a lot of tutorials, both online and in a book, and some of the others had more pics of the cooking process. But [i]yours[/i] is what got us through the actual process! Thanks again.

  28. calmir26 says:

    Hi again,
    I want to make this soap but in Romania doesn’t exist crisco. What can I use instead of crisco? ๐Ÿ˜ฅ

  29. calmir26 says:

    crisco means margarine?

  30. calmir26 says:

    thank you for your quick reply.
    I can calculate the new recipe if I know what concentrated are you use for water and super fat.I also need to know the ingredient who keep the soap with the same quality as before. It is possible? I need to make a soft, nourishing and hydrating soap for my daughter who’s skin is damage(?) by the chemical soap.
    Thank you

  31. calmir26 says:

    Hi, If I haven’t a Crock Pot I must use the bain-marie method or I can cook on the low open flame ?
    Sorry for my insistence(?)

  32. littlefeather says:

    Hi Calmir26,

    I’m making soap today, so I was on the site and saw your questions. You can make your own soap recipe with the oils and fats that you have using the soap calculator web page. It automatically calculates the lye and water for you, and sets the superfat ratio at 5%, as well as telling you the qualities of the soap your recipe will make. No math involved! The link is on Suzanne’s page, but here it is in case you can’t find it:

    I have hard water and dry, sensitive skin as well as being allergic to fragrances. I made my own recipe by playing around with amounts of the fats and oils until I had something that was very conditioning (67), but not too cleansing (7 – so it would be very mild and not strip the oils off my skin). My soap isn’t very bubbly (10) but it still lathers in my hard water. If you add 1 ounce (28 grams)of castor oil to your 2 pound batch (about 1000 grams?), it will really lather well, but still be very mild to your skin. I gave a bar of my soap to a friend, and her son’s eczema disappeared in a few days. He said it stopped stinging as soon as he used it.

    So experiment on the web page, and don’t worry if you’re qualities are a little outside the suggested ranges – you’ll get a warning if the recipe won’t work. I put in just olive oil in the calculator to see what qualities I would get, and they were outside the suggested ranges, but I know you can make soap with only olive oil, because I had done that years ago using the cold process. The calculator takes all the worry out of the process, and I’ve been having fun making soap (got 2 crockpots going today! One with milk – for the first time!).
    Good luck!

  33. littlefeather says:

    BTW Suzanne – thank you for your clear concise tutorial on hot process soap and your lovely recipes! I enjoy your stories because I used to live on a farm in VT and have a garden, etc., and your stories remind me so much of myself (chasing down horses after the deer took out a section of fence, dealing with all the produce from the garden, mud up to my ankles :D, and the antics of the animals). Now I just have a couple acres and am down to one horse and 2 dogs. And we have more snow than you here in GA!

  34. calmir26 says:

    Hi Suzanne,

    I decided to make neem oil soap using hot process.
    My question is: Can I add half of neem oil when the cooking is ready? I want to let half of neem oil uncooked. Can I?

    I want to use the next recipe:coconut oil 200g, oliv oil pomace 300g, calendula oil 100g, palm oil 150g, castor oil 100g, neem oil 150g, 33% goat milk, 131g lye (10% SF), 2 table spoons of honey.

    My son has dermatitis and this soap is for him.Will this recipe help him?

    Thank you.
    Daniela Craciun

    • Suzanne McMinn says:

      Daniela, have you run this through a soap calculator? I can’t make a judgment on a recipe. The recipes I post have been run through a soap calculator. If you put “soap calculator” in your search bar on Google or whatever you will find where you can use a free soap calculator online.

  35. calmir26 says:

    Yes I run the recipe through SoapCalc but I need to know if the oils that I choose and the quantity to each of them will give me a good soap.The soap have conditioning 62, cleansing 14, bubbly 23,creamy 31, and iodine 66.

    I don’t know what “iodine” means for a soap.

    Thank you for your time and help.


  36. smatheny says:

    Made this soap recipe and it didn’t trace….any ideas of what I did wrong?

    • Suzanne McMinn says:

      I don’t know…. I’ve never had this recipe not trace and have used it in many soapmaking workshops with participants also making it. The only thing I can think of is maybe mis-measuring, but there’s no way for me to know…..

  37. renecoston says:

    I’m planning to try this (oh, I am frightened at the prospect!) and want to use Pringles cans. Do you find that you need to press the soap in or that just spooning it in was enough?

  38. Nikki Gillette says:

    Thank you for the wonderful tutorial! I have linked to my blog because I want to share a very affordable laundry soap recipe but didn’t take photos of the soap process along the way. Thanks again, and you can see the recipe on the Rolling Pines Farm blog.

  39. magmom says:

    Made this last night! Thank you for the recipe and instructions!

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