Hot Process Liquid Soapmaking




Intro: Hot Process Liquid Soapmaking

This is how I make liquid soap, using all the natural oils and no surfactants. This results in a very mild, gently cleansing soap. I suggest you read "Making Natural Liquid Soaps" by Catherine Faillor, for more details and for beginner recipes.
With my process, there's no alcohol to add, no rigged up double boilers, and no bungee cords and plastic to tie to your pot. It literally cooks in the oven!

Edited on 7/22/10 to add:
Not having a recipe in this instructable seems to be a big problem for a lot of people, so I have decided to add one.  This is the recipe I used in this instructable:

24oz soft oil of choice (I use Soybean oil)
21oz coconut oil
3oz Cocoa Butter
12oz Lye
36oz distilled water (to dissolve the lye)

To neutralize: 3oz Borax + 6oz water heated until borax dissolves, then add to your soap
To dilute your soap: depends on how thick or concentrated you want your soap.

Here is link to some free recipes:
This instructable is only meant to serve as a 'picture guide' with basic instruction. It is written under the impression that the reader has some experience with soapmaking, and is looking to explore hot process liquid soapmaking. Please observe all the usual soapmaking precautions!
Check out my blog at

Here is a very basic list of what you will need.

Stainless Steel Pot
Stainless Steel Utensils (Very important, Lye will eat any other metal, and heat will melt plastic.
A very accurate Scale that will measure up to the size of your batch
Candy Thermometer
An assortment of bowls, and spatulas
Your oils
Distilled water (very important, tap water will keep your soap from forming. Not sure what spring water will do, I've never tried it.)
Your lye (Potassium Hydroxide, KOH, Caustic Potash)
Fragrance Oil.

Step 1: Weigh Your Ingredients

Make sure you are as accurate as possible. Usually there's a slighly higher lye amount used in liquid soaps than bar soaps, in order to make sure that the fats are completely neutralized. This excess lye will be neutralized later.

I make my liquid soap in an electric oven, set at 250 degrees fahrenheit. Your mileage may vary.
Set your oven to this temp when you first start weighing your ingredients, so your oven will be ready when you are.

It's usually better to weigh your lye and water first to allow some cooling time for the lye, as it takes the lye longer than the oils to cool. Remember, ADD YOUR LYE TO THE WATER, NOT THE WATER TO THE LYE, unless you like explosions in your kitchen.

Melt your oils in the big pot you will mix in, then add the lye water mixture, and commence to mixing!

Step 2: Mix, Mix, Mix

Let your lye solution cool down to about 140 deg F, and your oils to about 160deg F, give or take a few degrees.

This step is easier if you have a hand blender. Liquid soap takes a little longer to 'trace' than bar soaps. On average, it takes me about 15 minutes of on and off mixing to get to trace. Be careful not to wear out your blender. Once it starts getting warm, it's time to take a break.

This is what 'trace' looks like in liquid soap (Photo 2). It looks a little like applesauce, kind of thick and slushy. It's when your stock has thickened enough for you to raise your spoon/blender, and trail a 'trace' on the stock.

Now the fun begins.

Step 3: It's Oven Time...

Once you've achieved trace, then it's time to pop your stock in the oven with a lid.
I usually set my kitchen timer to 15-20 minute intervals to remind me to check the stock, otherwise I will end up with a burnt, congealed mass (This has happened to me before). The timer only works if you can hear it, so make sure you stick around...

From this point on, you're basically just watching, stirring, and waiting.

Step 4: 20 Minutes Later

Your soap looks like really thick white careful, the lye is still very much active.
You will stir the stock to make sure it's evenly mixed, then pop back into the oven.

Step 5: Another 20 Minutes

The soap is a paste. Stick your spoon in there, and you will find that there is liquid on the bottom. Alas, your paste has separated! No worries, this is normal. Just stir back together with a blender. Continue to cook.

Step 6: After an Hour...

Your paste will look like laffty-taffy. No matter how tempting, do not put in you mouth!

Shortly thereafter (another 20 minutes or so) it gets SOLID! From this point on, it will be pretty hard to stir, which is sort of okay, because you don't have to do too much stirring.

Usually at the point, you have bona fide soap, the lye and fats have fully combined. From this point on, you're working on the clarity of the soap. Do not stop here, however, as you still have to neutralize the remaining lye.

It is okay to leave your paste and go to bed now (if you're working late). You can turn off the oven and pick it back up in the morning with no problem.

Step 7: After 5 Total Hours of Cooking...

You will usually have a lovely amber colored translucent soap paste. Notice how the soap has bent my spoon while trying to stir.

This is the holy grail of liquid soapmaking, and you have found it! You want this color and translucence, because it means that when you dilute your soap stock with distilled water, it will remain clear, I promise you.

Step 8: Time to Dilute

It is now time to take your soap from stock solid, to ready-to-bottle liquid.
Please refer to your recipe/book for dilution ratios, tips and tricks.

Also at this point it is time to add your borax, which will neutralize your excess lye. Again, refer to your book for amounts. The borax also serves as an emulsifier. The nature of the soap (once diluted) is to congeal back together, but the borax serves to loosen that surface tension to keep your soap liquid.

This is also where you will add your glycerin, if you so desire. Glycerin adds an extra layer of emollient and moisture.

Stick your pot back in the oven, and continue to cook, until all the soap has melted into your water and you have a consistent texture.

Step 9: A Big Ol' Pot of Soap

Ready to be bottled and given to your friends and family.

I hope this has been helpful. It was done kind of in a hurry, so if there's any ambiguity, I apologize. Contact me with any questions.



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    36 Discussions


    9 months ago

    Very interested


    10 months ago

    i am going to try this tonite! i'm just going to bed now! thanks for sharing. have a great day


    2 years ago

    Very clover, conversational and involving type of instructables.


    2 years ago

    Thanks so much for this instructable. It's exactly what I needed. Also is the picture of the soap in step 7 hard or is it supposed to be soft? My tends to be soft so I keep cooking t thinking it's not done and it keeps bubbling. Also please help me figure this out, I've attached a picture. I used 60% olive pomace, 30% coconut 76 deg and 10% unrefined sheabutter and 5% supperfat. Is this layer my superfat or unsaponifiables. My Litmus paper turned green between 8-9 but the phenolp... remained clear

    bastille soap.jpg

    2 years ago

    thanks! I've been making cold process bar soaps for a while and now I'm looking into making liquid soaps as well.


    8 years ago on Introduction

    Very cool soapmaking tutorial.........what you said is true there is sooo much info on the web for bar soaps but almost nothing on liquid soap Thank you very much


    8 years ago on Introduction

    I know this is an old thread, but please know that recipes cannot be copyrighted. The description of HOW to make a recipe can be, but the basic ingredients cannot. As a courtesy, I would credit the source, but don't worry about're just sharing a list of ingredients and measurements, nothing that is protected by copyright's even questionable that the process to make soap could ever be protected (processes would have be a patent protection, not copyright, by the way) So share away in the future, and just be nice by saying where you found the information originally! from "Copyright law specifies that "substantial literary expression in the form of an explanation or directions," such as a cookbook, can be copyrighted but that a mere list of ingredients cannot receive that protection." In that regards, here's a recipe for liquid soap I found online! 16.5 oz. Sunflower Oil 7 oz. Coconut Oil 5.5 oz. Potassium Hydroxide KOH 16.5 oz. Distilled Water for the Lye Mixture 40 oz. Distilled Water to dilute the soap paste Either 2 oz. of boric acid or 3 oz. of borax mixed into 10 or 6 oz. of water Approx. 3 oz. Fragrance or Essential oil, as desired Soap dye or colorant, if desired Source:

    1 reply

    Reply 8 years ago on Introduction

    Hi! Thanks for checking out my instructable. I didn't include a recipe not so much because of copyright issues but because I meant this just to be about the process. Recipes abound on the internet with just a simple google search. I also did say in the instructable (above) that I used recipes from Catherine Failor's "Making Natural Liquid Soaps". I also included a link to snowdrift farms website for other recipes. I hope this helps. Yetunde


    9 years ago on Step 1

    You make a point to say that the lye needs to cool down, but how much? What temperature? What temp should the oil be when you add the lye? Isn't that important? I'm so confused, and I'm starting to get mega-discouraged with liquid soapmaking. This would be my fourth time.... *sigh*

    3 replies

    Reply 9 years ago on Step 1

    Please don't be discouraged! Once you get the hang of it, it's really quite simple. I will do an update to this instructable (and possibly a video) with more specific info, hopefully soon. I only meant this instructable to be general information to illustrate what to look for, but judging from what I'm hearing, people need more detailed information. To answer your question about the temperatures, I guess I didn't mention that because I don't worry too much about dropping the temps because it's not a huge drop. According to Catherine Faillor's book, you should let the lye cool down to about 140deg F (from the initial 150deg F that it rises up to). Tthe oils should be at about 160deg F. I will update with this info. Good luck, and please don't hesitate to ask if you have further questions.


    Reply 9 years ago on Step 1


    I've added my lye water to my oil. Following this method:

    And instead of a double boiler, I'm using a crock pot (propane is expensive where I live...)

    My mixture is not thickening.... How long should I be mixing for? I've been at it about 15 minutes, and it's still quite watery....

    Lye and oil added together at the aforementioned temperatures.


    Reply 9 years ago on Step 1

    Oh, you're so sweet! I'm doing this as I type, letting my lye cool down to the degree you said. Thanks so much for answering my question so quickly! This project has been vexing me for a week and a half now!! *cries* Heck, thanks for just answering my question period!! Five different sources, and not one answer until yours! <3


    9 years ago on Introduction

    If a person found it best to keep the soap in the condensed state, would it be best to neutralize the excess lye or not? Which do you think would keep longer? For example, I would only need a relatively small amount diluted, but it would be easier to do more at once.. My intuition says to not neutralize it to keep it less hospitable to nasties. Thanks

    2 replies

    Reply 9 years ago on Introduction

    hmmm...that's a good question. Even diluted and neutralized soap doesn't grow bacteria or mold, from my understanding. What does happen though, is that it goes rancid after a period of time due to the fatty acids in the oils reacting with the oxygen in the air. So, diluted and neutralized or not, it won't grow any nasties, but it will eventually go rancid, probably faster if undiluted and neutralized because the fatty acids will be more concentrated. I think it's always the best practice to neutralize the remaining lye in the soap. I think your purpose would be better served to add an antioxidant (such as T-50 vit E) to your oils as soon as you get them, before making the soap. I hope that helps.


    Reply 9 years ago on Introduction

    Thanks for the reply. A couple more thoughts.. One solution I was thinking about was using mason jars and either vacuum sealing or using a hot water bath to preserve it. If vacuum sealing, it would probably be best to neutralize as the fumes may deteriorate the sealer. If the oxygen is the problem, I would think the undiluted material would have less oxygen than the water it would be diluted with. Either way would probably be helped with the antioxidant idea.. Thanks!


    9 years ago on Introduction

    good instructable, i was wondering where do you get lye? Also for the borax can this be found in the detergent aisle? (99 Mule something?)

    1 reply

    Reply 9 years ago on Introduction

    Hi, and thanks for checking out my instructable. The lye for liquid soapmaking (Potassium Hydroxide) is a little harder to find than the one for bar soaps. You can buy some at either or
    Yes, the borax is 20mule team and can be found at your grocery store in the detergent aisle. Good luck, and I hope this helps!


    10 years ago on Introduction

    I was all good until the end when you said "check your book for ratios" This would be more helpful with a sample recipe.