Make Soap Using A Slow Cooker (Hot Process)

Posted 29 June, 2008 at 8:58pm by Tina Jiang

(Filed under: Soap Making)

63 comments to Make Soap Using A Slow Cooker (Hot Process)

Marie, June 30th, 2008 at 4:12 pm:

• tina - many thanks for posting up all your helpful tips and exeriences with soap making! i can't wait to start experimenting. hopefully i won't knock on your door too much and pester you questions happy soaping!!

Tina Jiang, July 1st, 2008 at 11:09 am:

• Marie, ask me questions any time :)!

gaga, July 5th, 2008 at 8:30 am:

• Wow, I've never tried soap making before but you make it look doable. Maybe one of these days I'll get up and try it myself! Thanks.

Tina Jiang, July 5th, 2008 at 2:42 pm:

• Gaga - I hope you give it a try :)! That's why I'm writing these articles - to demonstrate that it's not hard to do and that it's fun :D!

M. Lawyer, August 16th, 2008 at 5:24 pm:

• Tina - I just recently attended a soapmaking workshop by Kevin Dunn, and we made cold-process soap in 2 hours that was completely neutralized and solidified. I used within the week; it was perfectly set up and needed no extra curing - though I'm sure it wouldn't have hurt, only made the soap harder. It lathered up wonderfully!

  I think part of the difference is we used much less water in our lye - when you have less to start with, it cures much faster (since curing is all about removing moisture content). Also, with lower moisture content in your original recipe, the layers should not separate after trace.

  There is a little information on his website (www.cavemanchemistry.com) and he also has a book "Scientific Soapmaking" in revision right now.

  Regardless, I'm looking forward to experimenting around with both cold-process and hot-process soapmaking myself!

Tina Jiang, September 9th, 2008 at 9:20 pm:

• M. Lawyer - I checked out Kevin Dunn's website and it's very interesting! At some point I'd like to study the chemistry behind soapmaking and understand it better. I'll try making the next batch of soap with less water and see how it goes. How many oz of water did you use per 1 lb of oil/fats?

booda, September 30th, 2008 at 8:43 pm:

• can you please tell me how many soaps will it make with the given measurements?

booda, September 30th, 2008 at 11:16 pm:

• and oh! can we use aluminum molder since lye is already neutralized by the time we put the product in it?

booda, October 1st, 2008 at 1:41 am:

• you see.. I will be making soap that has a certain fruit as an active ingredient. will I only replace the almond meal with it? and will I remove some oil (because heavens there are so many kinds of oil in here!) so that I can see the real effects from the fruit? I mean, I will be using this for our investigatory project. if I use too many oils, we might not get to see what can "that certain fruit" do to our skin. We might just get the smooth skin just because of the oil. And that might just ruin our experiment. get it?

Tina Jiang, October 1st, 2008 at 9:48 pm:

• Booda, how many soaps you get depends on what size mold you use or how big you cut the pieces if you are using a box/pan/PVC pipe. For the recipe in this article, I got 13 pieces using the silicone muffin pan. You should be able to use an aluminum molder with hot process soap, as long as the right amount of lye is used and the soap has been cooked long enough for it to fully neutralize.

  For a simple recipe with only two oils, see my first article:
  http://www.orthogonalthought.com/blog/index.php/2008/05/homemade-natural-soap-basic-recipe/

  I've never made soaps with fruit in it so I'm not sure if the properties of the fruit will remain in the finished soap, but it doesn't hurt to experiment :). You can add it in place of the almond meal after the soap is fully cooked. Good luck and let me know how it goes!

booda, October 3rd, 2008 at 9:13 pm:

• but I've already read the cold process. can I replace the almond meal with it, and the water with the fruit *decoction?

  *- extracting process: the extraction of an essence or active ingredient from a substance by boiling

Jen, October 13th, 2008 at 2:32 pm:

• I've been making soap ever since you wrote the first soap article, and I haven't wanted to make HP soap since I like the smooth molded finish of CP. However, I bought a bunch of dried lavender to mix in the CP soap and although it still looks cool, it turned brown. I'm going to try it in HP some time soon to see if it might retain the purple colour that way.

  There are so many things to try and only so much space to store curing soap. augh!

Tina Jiang, October 13th, 2008 at 7:00 pm:

• booda, I would say try it and see what happens. From what I read it seems lye usually reacts with and destroys what is in the solution (e.g. scent, color, etc.) so not sure the beneficial properties of the fruit will remain in the finished soap. However if you make the soap without the fruit first then rebatch it (shred the soap, add some water or fruit decoction, melt it, then add the fruits) that might work better. It's best to try it and judge for yourself. Also I read that adding fruits to soaps will cause it to go bad faster, so you'll want to use it up quickly. Hope this helps.

Tina Jiang, October 13th, 2008 at 7:07 pm:

• Jen, I'm so glad to hear that you are having fun making soap :). Yes lye usually destroy color and scent of flowers. Adding it to HP may work (I haven't tried yet) - let me know how it goes! Also you can try rebatching CP soap and add the lavender that way. After the CP soap has cured for a week or so - shred it, add some water, melt it in a double boiler or microwave (take care not to overheat - start on half power and 30 seconds at a time), then add the flowers. It's a bit of a hassle but worth trying at least once. Good luck!

Adam, October 24th, 2008 at 5:20 pm:

• Tina,
  I have a question:Do you have to put the almond meal and fragrance oil in the hot process soap?

Tina Jiang, October 25th, 2008 at 3:54 pm:

• Hi Adam, no you don't have to put the almond meal and the fragrance oil - they are optional additives. By leaving out the fragrance oil you will have an all natural unscented soap (fragrance oils contain synthetic ingredients), which is good for people with sensitive skin. The almond meal gives the soap exfoliating qualities which some people really like. Most of the soaps I make have FO added since I like the scents and sometimes I add oatmeal or almond meal for the scrubby effect but it is totally up to the soap maker :).

Jen, October 26th, 2008 at 3:46 pm:

• so I tried making HP soap the other night and I'm not entirely sure I cooked it long enough. I don't have a slow cooker, so I did it double boiler style with a glass bowl in a pot of water on the stove. Anyway, might be worth giving one more try. This time the lavender flowers turned grass green instead of brown.

  I also made a batch (CP) a few weeks ago with powdered green tea. I was not surprised that the green turned brown (in fact, it seems to be a pretty dramatic oxidation reaction - the molded surface doesn't turn brown until after unmolding, and when you cut it up, the green cut surfaces turned brown after a couple of minutes) but it got shockingly dark. If my uncoloured soap reminds people of white chocolate, this stuff looks like dark chocolate. And the lather is brown, too, and although it rinses off, I'm worried I'll stain people's bathroom fixtures, so that was kind of a failed batch. I think I'll grate it up and sprinkle small quantities to speckle future batches a little, but not so much that it will stain the fixtures.

Alison, October 29th, 2008 at 3:41 am:

• Hi Tina

  I've recently had a go at the cold process soap and it's worked out really well - thanks! My hubby is going through it a great rate of knots and my sister has already nicked some and is demanding more! LOL

  I was wondering though, with the hot process recipe, can I replace the palm oil with anything? I can't seem to find any palm oil locally (and I like to use local or fairtrade ingredients if I can) so could I use extra coconut oil or shea butter instead? Any thoughts you have would be appreciated

Tina Jiang, October 29th, 2008 at 9:06 am:

• Jen, thanks for sharing your notes on adding flowers and powdered green tea to cold and hot process soaps! Please keep trying so the rest of us can learn from your experiences :). Thanks!

Tina Jiang, October 29th, 2008 at 9:30 am:

• Alison, I'm so glad to hear that your CP soaps have been successes and that your family is benefiting from it :D! Yes you can replace the palm oil with other oils - just need to use a lye calculator (http://www.the-sage.com/calcs/lyecalc2.php) to make sure the right amount of lye is used for the combination of oils you are using. The other thing to consider is that palm oil contributes to the hardness of the soap, so if you prefer firmer soaps it would be better to substitute with oils that are solid at room temperature, such as coconut oil, shea butter, cocoa butter, or vegetable shortening (or tallow and lard if you don't mind animal fats). I read that too much coconut oil can be drying to the skin so try to keep it under 30% of the total oils. On the other hand I think it largely depends on personal preferences and experiences so I recommend you experiment a lot and figure out what works best for you. Good luck and happy soaping :)!

Anonymous, October 29th, 2008 at 7:11 pm:

• wouldn't suggest using aluminum with hot process either. same reason the soap will still "burn" your skin if you use it before it sets. I always sample a small blob of soap scraped off the crock pot after i fill my mold and if i don't let it set up first, it seems to be lye heavy. so if you put it in an aluminum pan, it may still cause a problem.

sam, October 29th, 2008 at 7:21 pm:

• Jen, I share your struggles with green tea. I've used it in several batches and each one turned dark brown. Yes it will stain fixtures, my mother-in-law threw hers away because of it. It's still good soap, just a hassle. I did find that if you want to put tea leaves into the soap, run hot water over them first and squeeze them "dry". Then add them just at the end of cooking the soap. It will keep the leaves from dying the soap and if you want a green look you'll need to use dye. If you don't run them through water first, they will cause the soap to go brown. But from what I can tell, no matter when you add any tea solution, it will turn brown. Hope this helps.

Anonymous, October 30th, 2008 at 6:40 pm:

• darn it, i used "drain pipe sosa powder".

  contents: caustic soda, aluminum pellet, catalyst

  ehhh?? :(( heeeeelp

Tina Jiang, October 30th, 2008 at 7:05 pm:

• Please throw away the soap - there's no way to save this batch. Start fresh and wish you luck with the next batch using pure sodium hydroxide!

Evergreen, November 10th, 2008 at 6:23 am:

• Can any soap recipe be made with a slow cooker, or does it only work with certain recipes? I'd like to make shampoo bars with the slow cooker, but wasn't sure it would work.

Tina Jiang, November 10th, 2008 at 8:19 pm:

• Evergreen, you should be able to make most soaps with a slow cooker, including shampoo bars which just require different oil combinations. Good luck!

Evergreen, November 11th, 2008 at 7:26 am:

• Okay, thanks!

Lady Lavender, November 14th, 2008 at 12:38 pm:

• TINA: thank you for a great, detailed, and not scary description of the soapmaking process.

  JEN: i have made a cold process soap with our lavender (we have a lavender farm). It makes a great "scrubby" soap, even if the lavender turns brown after curing. The lavender flowers stick out from the bar of soap and work as a mild scrubbing agent. It is great for gardening or working hands. And most people think it's oatmeal, so the brown color doesn't bother them.

Elaine Kochar, February 2nd, 2009 at 10:02 pm:

• Hi Tina,
  Yesterday made my first batch of soap in the slow cooker. It has an autamatic setting which is what I put it on after the soap traced. Well! i left it for five mins and when i came back the soap had boiled over and out fo the crock pot! Scooped it all back but it refused to do anything else. IT stayed a little away from the edges and just sat. Not boiling , no nothing. so I added a little water and then heated it on slow and automatic alternately for hours and hours.. well at least five hours! Was like thickish apple sauce but never turned quite into mashed potatoes. Then at the end of my patience and as the edges had white dry pieces and lots of cry flakes but the middle refused to dry up totally. tasted and tasted and tasted hoping it would at least neutralise so I could use it as glakes to wash dishes.. but except for a crop of blisters on my tongue , no change. So took it out. bravely washed my hands with some of the flakes and put it into a mould. If I wash my hands its fie! When i taste it it still burns. Should I throw it away, let it sit for two weeks? Use it? HELP!
  Am bravely starting another batch following your pictures which I found today. I dont have a very accurate weighing machine, one of the old kitchen scales in gms.
  Would love some advice.
  Elaine

Tina Jiang, February 10th, 2009 at 9:59 pm:

• Hi Elaine, I'm so sorry to hear about your unfortunate experience with your first batch of hot process soap! It's hard to say if the soap is lye heavy without testing it with ph paper or phenolphthalein, so I would say be safe and throw it out. I've never tried the tongue test since I don't like tasting soap :-P. For the most part I've relied on using a good weigh/scale and having relatively accurate measurements. The consistency of the soap will vary depending on the amount of water you use - like apple sauce with more water, or like mashed potatoes with less water. I stir the soap once or twice during the cooking process to make sure it's well blended in case the glycerin floats to the top (doesn't always happen). Also I try not to fill the slow cooker more than two thirds full to avoid boil overs. Hope this helps!

annenurse, March 3rd, 2009 at 10:54 am:

• Hi Elaine, I am new to Soapmaking myself. I read a recipe were you put your soap after it reaches trace into the oven at about 200 degrees and let it bake for 1 to 2 hours checking it every 30 minutes. It is like the HP process and the soap looks like applesauce when it is done. So far I have made 2 batches and they turned out okay. So when I make soap I make enough to have a batch for CP and a batch for CPOP so that I can start enjoying them right away since I don't have much patience. Happy Soaping

s.c., April 16th, 2009 at 7:12 pm:

• my slow cooker soap looks ok, except for alot of liquid seeping out of the bars.it is little small oily looking bubbles.i added melted beeswax at trace.

Elizabeth, May 10th, 2009 at 6:39 pm:

• Hi. Just wondering if you can use the slow cooker again afterward for cooking or if once you use it to make soap , it cannot be used again except for soapmaking? THanks

Tina Jiang, May 17th, 2009 at 9:36 am:

• I recommend using the slow cooker only for soapmaking just to be safe…

Heather, August 3rd, 2009 at 2:02 pm:

• We have recently purchased some dairy goats and have more milk than we can drink. I am interested in making soap with the extra milk we have.
  Can I just use goats milk instead of the distilled water?
  Thanks for your help.
  Heather

Elaine Kochar, August 3rd, 2009 at 11:43 pm:

• Tina, thank you for your advice in Feb. Have made another perfectly good olive oil soap after that.
  There is a question though, I am going to use vegetable fat, along witholive oil and coconut oil. The lye calculators dont give this as an ingredient so its difficult to know if the lye is right. May I use the same amout of lye as needed for , say, palm oil, or sunflower oil? It should work approx. You think?

Aziz yasin, October 10th, 2009 at 11:59 pm:

• Its oky but tel us the of material

Catherine, October 20th, 2009 at 4:27 pm:

• Hi Tina,
  Three days ago, I made the very first olive oil soaps from your first blog. However I think I overtraced the oil and lye mixture as it was too thick to pour to the mold. I scooped it into the mold though. Can I use the soaps? Do you have any advise when this happens again?

Elizabeth Szucs, October 20th, 2009 at 8:22 pm:

• I had some problems before with overtrace and pouring into the mold and mine worked out fine, just not completely round on top. And Elaine, I have used goat milk, but I usually use it with a specific goat milk recipe. (I'm not Tina, but I saw the questions and just decided to respond). I started making soaps last May and love it!

Tina Jiang, October 23rd, 2009 at 9:55 pm:

• Heather,
  You can use milk instead of water, but the steps needs to be modified since the milk will cook and may affect the consistency/texture of the soap. Unfortunately I don't have any experience with hot process soap using milk but perhaps Elizabeth can share her recipe?

  Elaine,
  What kind of vegetable oil is it? If it's soybean oil (most common vegetable oil) then it is included in the lye calculator.

  Catherine,
  Overtracing the soap doesn't affect the end result - it just makes it harder to pour and smooth out. The soap is fine to use. When I'm mixing the soap using the stick blender, I also stir it in a figure 8 motion so I can feel the consistency of the mixture. Once it turns from transparent to opaque and I start to feel it becoming thicker, I stop every few seconds to check if the drippings from the blender leaves a pattern on the surface of the mixture. When it does, I stop blending and pour it into the mold. As usual, practice makes perfect - I'm sure you'll get the hang of it after a few tries :).

Michael, October 24th, 2009 at 8:41 am:

• Tina,
  Thanks for your easy to understand directions. Three batches done and it's wonderful soap. Found a crockpot, stick blender, large plastic bowl, 2 quart glass bowl (narrow & tall for lye), silicon spatula and wisk for 20 dollars at thrif store. Would like to pass on some ideas for other soapers: great source for lye is http://essentialdepot.com (1/3 Lowes price for food grade, ships in 2 lb bottles, 8 lb maximises shipping). Also found store brand (generic) shortning made of 100% Palm oil, others soybean. Resturaunt supply store good source for 100% coconut oil sometimes listed as popcorn oil. Can get unflavored coconut oil if you ask them (they order it, if not in stock:50 lb for $60.00 best deal to split with friends). I use milk cartons (single use) and parchment paper lined bussiness card boxes for molds. Hope this info helps to save on costs for people. Happy suds

Elizabeth Szucs, October 27th, 2009 at 8:17 pm:

• Goat Milk Soap Recipe
  11.3 oz coconut oil
  11.7 oz palm oil
  15.5 oz olive oil
  3.9 oz almond oil
  6.1 oz lye
  15.5 oz goat milk
  2 1/3 tablespoons essential oil (I used lemongrass)
  1 tablespoon almond oil

  I loved this recipe! Freeze your goat milk in a plastic ice cube tray until slushy and then add your lye very slowly. THis will keep it from heating up too quickly. After trace add your essential oil and the tablespoon of almond oil. Cure for 4 weeks. No temperature was given for the oils or milk lye mixture. Enjoy! IF you don;t have goat milk you can use any milk you have at home.

Catherine, November 10th, 2009 at 2:12 pm:

• Elizabeth, thank you for sharing the Goat Milk Soap recipe since, I was trying to find the recipe. I have a question. Do I have to use the essential oil? What happens if I don't use it? Can I still make a soap? One more question. Is the soap very creamy and moisturizing? I have a kind of dry skin.

Elizabeth Szucs, November 10th, 2009 at 6:21 pm:

• Hi Catherine,
  YOu will love this soap! It is very creamy. I suggest goat milk, that will turn out even creamier. It is ok if you don't have the essential oils. The milk will turn a light brown color. If you add the lye slowly, it shouldn;t change colors so fast (some people prefer white soap).I have another one with oatmeal. I will try to dig it up and post it here. Enjoy!

Janice, December 8th, 2009 at 8:11 pm:

• Hi Tina,
  Is there a difference between palm kernel oil and palm oil? If so, can I use the same amount of palm kernel oil for the receipe you provided? I live in Silicon Valley and the closest thing I could find to palm oil is at Whole Foods which carries shortening; I believe the ingredient was mainly palm oil. Any other recommendations on where I can buy palm oil?

elizabeth, December 9th, 2009 at 7:53 am:

• Try AAA chemicals
  http://www.aaa-chemicals.com/
  It is difficult to find palm oil. I have been having the same problems. Hope this helps
  Elizabeth

wendy, December 14th, 2009 at 9:31 pm:

• I was planning to use stainless steel muffin pans as molds for some soap. Do you knowif I can line it with paper muffin cups to make it easier to get out? Will it be difficlt to remove the paper? Do I need to remove the paper to cure the soap? I was planning to use the CP method.

  Thanks for any help you can offer.

Ellen, January 1st, 2010 at 11:25 am:

• I am just starting to make soap myself. I am interested in hot process but so far have only been using cold. I am finding palm oil at Wholefoods market and some of the larger Ralphs supermarkets. Wholefoods also carries jungle shortening which is a little more expensive. I have been looking in Asian groceries, and I'll bet if there are Indian or Asian markets in your area they might carry both coconut oil and palm shortening.

Mary, February 13th, 2010 at 8:07 pm:

• I have been making soap for a while now, and have had good success using aluminum molds for hot process soap. I have a number of old aluminum jello molds that make very attractive soap. I just use a damp sponge to rub off the "Jello" trademark when I unmold the soap. Some of the molds are so old that the Jello word still has a hyphen in it as it did years ago. Also, a hint for getting soap out of PVC pipe. If you use a 3" size, just put a can of soup or milk on the counter and lower the pipe of soap over it. The soap will push right out the top. Just don't push the can all the way into the pipe! In my area of NM, the Smith grocery and Sunflower market both carry a brand of vegetable shortening that is palm oil. Somewhat expensive, but unless you are making mass quantities of soap, it is cheaper than paying for shipping. If you aren't hung up on all vegetable soap, I have found that lard makes a very similar product at much less expense in my recipes. Thanks for a very nice site!

Anna B, February 17th, 2010 at 1:28 pm:

• Tina -

  Excellent article, very clear and well written! And great photos too. Thanks so much for simplifying this tricky topic. I have enjoyed all your related soap posts.

  Anna

marie, February 22nd, 2010 at 9:31 am:

• do you turn off the crock pot before adding the lye

Beth, April 3rd, 2010 at 8:41 pm:

• Can u use rosemary extract as a preservative in soaps? If so, how much and do u add it like u would FO? Thank u so much for all the info and teaching.

  Beth

Rashda Saleem, March 23rd, 2012 at 8:03 am:

• I made hot process soap from which glycerin separated just as the soap was ready. No matter how long i heat it afterwards it didn't dissolve. I added a little amount of lye solution to it twice and cooked but it only got from bad to worse. Need help…

Rashda Saleem, March 23rd, 2012 at 8:05 am:

• How do i add fresh fruit to hp soap

lizzykat, April 19th, 2012 at 3:31 pm:

• wow thanks so much for the detailed descriptions and pictures really helped me to make my first batch of hot processed soaps!
  very detailed and simple to use

Michelle, May 1st, 2012 at 7:05 pm:

• Tina

  Hey Tina how are you doing? I was wondering have you done any new soap blogs?

  You fan
  michelle

Annie, May 6th, 2012 at 10:43 pm:

• Made my first batch yesterday, pretty impressed with it, would like to make a whiter one, did you have a recipe or do we need to add a whitener, and can you add coconut cream or powder to give it a milky appearance
  thanks

J. C., June 23rd, 2012 at 9:47 pm:

• I just made my 1st soap HP and it was 16oz of olive oil and 16oz coconut oil. I douled the coconut oil by error. Can I used this soap and remelt it and double the rest of the ingredients and save the batch.It is very oily and did not set after the 2 hours.

Holly T, August 9th, 2012 at 2:43 pm:

• I actually have a question for you. Is there a reason you use coconut and palm oil, I guess actually the palm oil would have no smell, but does the coconut oil? I do not like the smell of coconut so was wondering if there is any substitutes? Looking forward to starting with the cold press soaps first and then going on to the hot press. Thank you for all the information.

Tina Jiang, August 9th, 2012 at 3:14 pm:

• The coconut oil has no smell… this recipe makes unscented soap unless you add essential or fragrance oil to it. Coconut oil is important in soap recipes because it provides lather/bubbles, and palm oil provides firmness.

Paul Austin, January 13th, 2014 at 12:32 pm:

• I have a problem with my lye in that it comes in plastic containers that carry a static charge, or the lye does, and the lye flies out of the containers when I pour it. I've tried a few ways of dispelling the charge but it never seems to work (touching to metal, using a dryer sheet, etc.) Have you ever had this happen? It's dangerous to even get a few grains of it on your skin, and it flew all over the kitchen counter once and into some food. I should probably just dump it in a large glass jar if I can find one.

  Thanks for your site, I use your first recipe a lot!

Kelly, February 28th, 2014 at 10:59 am:

• I love all the info here. Can I use goat milk in hot process soap?
  Thanks so much.

June, March 21st, 2014 at 6:33 pm:

• Thanks for these instructions that leave out the suggestion to test your soap by seeing if it zaps your tongue. I made some soap and linked to your blog from mine.