Note: What follows is a complicated method for making liquid soap based on Catherine Failor’s book on the subject of clear liquid soap. I wrote this post five years ago, and have gained a lot of experience in the meantime. If you read this tutorial and want to tear your hair out, see how I make liquid soap now, the easy way, here.

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In preface to this post, I want to say that this isn’t the only way to make liquid soap. In fact, the more I research liquid soap, the more I realize how inventive, creative, and limitless it is. What I’m going to present in this post is how to make clear liquid soap, using Making Natural Liquid Soaps by Catherine Failor, among other resources.

Liquid soap, like any soap, is created by combining fat with lye. The fat can be all sorts of things–-but for liquid soap, as opposed to hard soap, coconut oil (for lathering) in combination primarily with soft oils is generally recommended. Soft oils are oils that are liquid at room temperature (such as olive oil). You can use hard fats, but if you are in pursuit of clear liquid soap specifically, it may make your effort more difficult. When formulating your own recipes, research the types of oils/fats you want to use. Even amongst soft oils, every oil behaves differently.

The lye used in solid soap is sodium hydroxide, otherwise known as caustic soda. Liquid soap requires a different type of lye–potassium hydroxide (caustic potash). Potassium hydroxide is more soluble than sodium hydroxide, which makes liquid soap possible. The same safety precautions remain–use goggles and gloves when handling potassium hydroxide, avoid inhaling fumes, and store securely out of reach of children and pets. (Review safety precautions here.)

You don’t have to learn how to make solid soap before learning to make liquid soap, but if you’ve already tried your hand at solid soap, you’ll find some of the procedures in liquid soap to be comfortingly familiar.

When pursuing clear liquid soap, it’s important that all the fatty acids are saponified (to avoid cloudiness or separation). For that reason, clear liquid soap recipes are formulated with a lye excess. Potassium hydroxide flakes intrinsically contain water and other impurities, around 10 percent, which means the lye excess in clear liquid soap recipes is not as high as it initially appears. Even so, this soap must be further neutralized to get rid of the excess and lower the pH. This is done by adding a solution of boric acid, borax, or citric acid after diluting the soap.

Do you care if your liquid soap is clear? Maybe not. Many liquid soap crafters begin with the lye excess method then move on to creating their own opaque liquid soaps without lye excess and no added neutralization. This is a slightly perilous path for the beginning liquid soaper because there isn’t a lot of expert information available to the home crafter. I’ve already experimented with a recipe that way, and had a failure with it. I learned from that failure, and will continue to experiment. If you are interested in pursuing that path, you will want to do your own research and learn to formulate your own recipes. To formulate liquid soap recipes without lye excess, I recommend the recipe calculator at Soap Calc here. As I said, slightly perilous path for the beginning liquid soaper due to the research required in this pursuit. In my opinion, it’s best suited to the advanced liquid soaper.

Keep in mind that you will find liquid soap calculators at many sites, but they are often calibrated to a lye excess. (And there’s some confusion about it.) I’ve seen Summer Bee’s calculator referred to as a 0 percent calculator, but it’s not. It’s calibrated to a lye excess, and they state that on their page. The liquid soap calculator at Bramble Berry is also calibrated to a lye excess. (Run any Failor recipe through them and you’ll see.) If you want to calculate your own recipes using the lye excess method, I recommend the Bramble Berry calculator. It’s dead simple. However, there are some additional features at the Summer Bee calculator that aren’t available elsewhere, so it’s a handy resource for more advanced formulations.

You can also find a wealth of information from fellow liquid soapers, many of them working with recipes with no lye excess, at the Yahoo Liquid Soapers group. I’ve also opened a topic for discussion and questions about making liquid soap on the CITR forum here. (Come join us!)

Meanwhile, if all that is too much for you as a beginning liquid soaper, I recommend starting with the lye excess/added neutralization method, for which the most expert information is available for the home crafter. In every recipe I’ve tried, I’ve found this method to be no-fail. If you’re after immediate gratification, have I got the liquid soap for you!

No matter what kind of liquid soap you’re making, it all starts with cooking a soap paste, which is then diluted into liquid soap–and it’s super easy. Let’s go! (Specific recipes follow.)

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How to make a soap paste:
Prepare your work area. Gather all tools, utensils, safety gear, and ingredients. Along with a large (unchipped) enamel crock pot, you will need a number of bowls and utensils for holding, measuring, stirring, etc. Do not use aluminum, tin, or copper. Use stainless steel, glass, or heat-resistant plastic for your bowls and utensils. You will also need a kitchen scale and a stick blender. (Note: You may want to weigh your crock, empty and removed from the outer heating pot, before you start. I’ll explain below.)

Weigh the oils and place in the crock pot on Low.

Prepare the lye solution. Weigh soft or distilled water in a large bowl.

Weigh the lye.

ALWAYS ADD LYE TO WATER. NEVER ADD WATER TO LYE. Add the lye gradually, stirring constantly. (I was taking a picture, but otherwise you should be stirring.)

The mixture will appear cloudy at first.

It will quickly clear.

Pour the lye solution slowly into the warm, melted oils. Your crock pot remains on Low.

The mixture will darken and not look very appealing.

Place the stick blender in the crock pot, making sure the blade is completely immersed in the mixture to avoid creating splatters.

The mixture will turn opaque and become thicker and smoother as you blend it. To avoid burning up your stick blender, blend with it on for a few minutes, then turn it off and just stir with it. Then on, then off, as you watch for the mixture to come to trace.

What is trace? Trace is the stage in soapmaking where you can draw a line across the mixture and it will remain visible for several seconds before disappearing. (Sort of like when you’re making a thick gravy or a pudding.) Trace is even easier to recognize in a liquid soap recipe than a solid soap recipe. In fact, you can’t miss it. And it will go from starting to thicken to trace so fast, you will be lucky to get your stick blender out in time.

Right before trace:

A minute later, so thick I can’t shake the mixture off the stick blender, I have to scrape it off.

With the crock pot still on Low, put on the lid and begin the cook. Check it a couple of times during the first 30 minutes to be sure there’s been no separation of the oils. If you see any liquidy oils at the bottom of the crock pot, stir them back in.

The mixture will quickly become so thick, a spoon will stand up in it.

The paste will become very difficult to stir during the cook. Do your best. You can try a potato masher. It’s nearly impossible to stir at some points. Check the mixture about every 30 minutes during the cook and stir/break up/move it around the best you can to continue to mix the mixture as you watch for signs of finished paste.

Finished paste looks like thick Vaseline with a translucent quality.

Another look at a finished paste:

Finished paste close up in a sample:

How do you know if your paste is finished? Aside from looks, you’ll need to dilute a sample to test.

Testing for finished paste:
Dissolve 1 ounce of soap paste in 2 ounces of boiling distilled water. If it tests clear, your paste is done. If it tests slightly cloudy but you’ve cooked for the expected period of time, that’s okay, you’re done. If it tests milky, you are so NOT done. (If it tests milky forever, you did something wrong. Probably mis-measured something.) In the recipes below, I’ve given you my cook times per recipe. Don’t test sample constantly. Wait at least 3 hours before test sampling, and then test sample about once an hour. Don’t be impatient, grasshopper. (Extra cook time will not hurt your soap, so never fear.) Tip: Start with 2 ounces of boiling water and the 1 ounce of soap paste–then zap 45 seconds in the microwave, stir, zap again, stir, zap again, several times over and your test sample will dissolve more quickly.

Sample testing clear (the paste is done):

Sample testing cloudy (this is still done):

Sample testing milky (NOT done!):

Once your paste is finished, weigh it. (You will need this information, and soap paste weight can vary, even when using the same recipe a second time, due to even slight differences in measurements, cook time, and evaporation.) You can either weigh your crock pot before you start (crock removed from outer heating pot) or remove the paste to weigh. I weighed my pot, but found later that when I tried to weigh the pot and paste combined, my scale couldn’t take it. It’s a pain, but not impossible, to remove the paste to weigh. Scrape it out with a big spoon and transfer to a bowl. You don’t have to get every last bit, just close enough. (Weigh the bowl first to deduct from the total weight or hit tare after you place the bowl on your scale and before you add the paste.) Weigh the paste, then return it to the crock pot.

You may at this point want to store half the paste for later use. As you move the paste back to the pot, keep your bowl on the scale and weigh out half the paste to return to the crock pot. Store the other half in a plastic baggie labeled with the recipe name and the weight of the paste for future reference. Depending on your rate of dilution, you might not even be able to dilute the entire paste in your crock pot anyway, but you will have no trouble diluting half the paste in your crock pot even at 20 percent dilution.

Another reason to divide your paste in half, or even in thirds, is to experiment with different dilution rates in preparing the soap. You may also want fragrance it in separate batches to please family members or friends, or make one part unscented for someone who doesn’t like scent while still fragrancing the rest. When you divide the paste, you have room to play with each part separately in dilution, scent, color, thickening, and so on.

Dilution:
Use soft or distilled water to dilute your paste. Here is a dilution table showing percent of soap and percent of water added per pound of paste.

For 15 percent soap — 48 ounces water (3 pounds) added per pound of paste
20 percent — 32 ounces (2 pounds)
25 percent — 22 ounces (1 pound 6 ounces)
30 percent — 16 ounces (1 pound)
35 percent — 12 ounces
40 percent — 9 ounces

Soaps made from 100 percent coconut oil will dilute at 40 percent (though that would be a very drying soap). You will have a hard time getting a recipe with any significant amount of olive oil to dilute at anything other than 20 percent. I started out trying all of my recipes at 30 percent. If a soap doesn’t dilute in a reasonable period of time (several hours) then you’re probably at the wrong dilution rate. A soap that isn’t going to dilute at your current dilution rate will start forming a layer on top. No matter how many times you break it up, it will keep layering.

An olive oil soap layering at 30 percent dilution:

You have two choices. You can either dilute the soap further, or emulsify it with a 33 percent borax solution. Emulsification with a borax solution allows you to dilute soap at higher concentrations. Your other choice is to dilute further then thicken with glycerin. Borax is a natural mineral/salt. Glycerin is a byproduct of soap fats. Which path you choose will depend on the type of soap you’re making, its intended use, and your personal preferences. I used a borax solution to emulsify my home cleaning soap at 25 percent. For my hand soap and shampoo, I chose to dilute to 20 percent then thicken back with glycerin.

Your diluted soap weight = the weight of your paste plus the weight of your dilution water. (You will need this information, so after you finish diluting, add it up!)

Emulsification:
To emulsify liquid soap at a higher concentration than it will naturally dilute, add up to 2-3 tablespoons borax solution per pound of diluted soap. (See how to make a borax solution below.) If you choose to emulsify a recipe, you don’t need to add any further neutralization. You can do this before or after sequestering, but if you do it before sequestering, your soap is as clear as it’s going to get because this level of borax solution addition will interfere with further clearing.

Neutralization:
You can neutralize your liquid soap one of three ways–with citric acid, boric acid, or borax. You will add this to your diluted soap, but the amount you add is based on your paste weight.

To make a citric acid or boric acid solution (these two solutions are made at 20 percent), add 2 ounces of citric or boric acid to 8 ounces of boiling distilled water. Stir until dissolved. Use while hot. Add 1 1/2 tablespoons per pound paste weight to neutralize.

To make a borax solution (made at 33 percent), add 3 ounces of borax to 6 ounces of boiling distilled water. Stir until dissolved. Use while hot. Add 1 1/2 tablespoons per pound paste weight to neutralize. (Borax means, for example, the 20 Mule Team stuff.)

Following neutralization (or neutralization by emulsification), while your liquid soap is still hot, add (if using) scent, coloring, superfatting, thickening (if by glycerin), and sequestering agents.

Scent:
Add fragrance or essential oils, if desired, at 2-3 percent of your diluted soap.

Coloring:
You can dye your soap with specially prepared liquid soap dyes or use food coloring from the grocery store. (No, this won’t cause staining.) Fabric dyes are not recommended for liquid soap. Add color gradually–a few drops can color a lot of soap! Take into account that you are, with most clear liquid soap recipes, starting with a light to dark amber natural color.

I did color experiments in small samples, just for fun.

I usually prefer my homemade soaps in their natural color.

Superfatting:
Sulfated castor oil is the only recommended oil for superfatting liquid soap because it is completely water soluble. Other oils will cloud your liquid soap. Superfat at 1 percent of the diluted liquid soap weight.

Thickening:
For thickening purposes, add 1/2 to 1 ounce per pound of a 33 percent borax solution per pound of diluted soap. (Add to cold–aka room temperature–diluted soap.) If your soap is cloudy, do NOT use a borax solution for thickening until after sequestering. (This is more borax solution than used in neutralization and can interfere with clarity before sequestering.)

If you don’t want to use borax to thicken, add 1-2 ounces of glycerin per pound of diluted soap instead. Glycerin will also add moisturizing, lather, and emollience. You can add glycerin for thickening before sequestering as it is also a sequestering agent. Start with 1 ounce per pound diluted soap. Don’t expect to see the results of the glycerin until the soap cools and sequesters. After sequestering, if it’s not as thick as you like, you can add more.

Sequestering Agents:
You will already know from your test sample if your soap is slightly cloudy–and you can fix it now. (This will NOT fix milky liquid soap!) To clarify slight cloudiness, you can use isopropyl or ethanol alcohol, a sugar solution, or glycerin–or a combination of all three. Whatever mixture of sequestering agents you choose, add them at no more than 5 percent of your diluted liquid soap weight. To make a sugar solution, bring 1 pound of water to a boil. Add 1 1/2 pounds of sugar. Bring to a boil again and cook until the sugar dissolves.

Sequestering is the time the liquid soap sits before it clears. Some soaps are clear immediately. Others take days or up to 2 weeks to clear. Your liquid soap is ready to use immediately after you finish making it, but you may want to sequester some recipes for added clarity. I transfer my liquid soaps to quart jars for sequestering and storage. You may want to use something else, but clear glass enables you to see the soap as it’s sequestering, which is handy if you are looking for clarity. Save your empty water jugs and, after sequestering, transfer your soap to them for longterm storage and use to refill your dispensers.

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Recipes:
The Failor book is a fantastic resource and I highly recommend it. The book’s drawbacks are the way the information is organized and the lack of detail presented with the recipes. You have to flip back and forth hunting all over the book to find what you need when you need it, and recipes give no hint to suggested soft oils, recommended dilution rates, probable cook time, likelihood of cloudiness, etc. I’ve done my best with this tutorial to present the information as you need it, and to specify exactly how I made each recipe. These recipes are all adapted from the Failor book. You can replace the olive oil in these recipes with another soft oil (or combination of soft oils) and alter the dilution rate and other matters to your liking. If you do so, your results may be different. Feel free to experiment! For even more recipes and a lot of great resource information, get the Failor book. You can also create your own recipes using a liquid soap calculator.

Each of these recipes, the way I made them, yielded about 6 quart jars of liquid soap. Each quart jar of liquid soap weighs approximately 2 pounds, so that’s 12 pounds of soap!

I didn’t superfat any of these recipes, but you can. Remember also that if you want to dilute at a different rate, you could dilute all of these recipes at 30 or even 35 percent if you don’t mind emulsifying with a borax solution to the fullest recommended emulsification allowance. Homemade liquid soap is typically thinner than store-bought liquid soap. (Store-bought liquid soap is thickened.) How you make your recipes is all about what you want–do it your way.

How much did these soaps cost to make? I don’t know. I don’t like math and I didn’t figure it out. If you want the cheapest liquid soap possible, you can buy store-bought liquid hand soaps and shampoos for a dollar a bottle. You may not be able to make homemade liquid soap for that–but then, you might not want to know what’s in your cheap store-bought liquid soap. If you want to make homemade liquid soap for frugality purposes, find the best deals on lye and coconut oil. Use the cheapest soft oils you can find. Use borax to emulsify and thicken (borax is cheap) and don’t use any essential oils. If you want to make homemade liquid soap out of an interest in the craft or to provide the most natural, quality product you can for yourself and your family, then you will choose your ingredients with those goals in mind. (And your soap won’t be quite as inexpensive.) How much your liquid soap costs is up to you and it’s all about your perspective.

Moisturizing Hand Soap with Jojoba:

Notes: This recipe yields an initially slightly cloudy soap due to the jojoba. You’ll need to use sequestering agents to clear it up, and it will require sequestering time to clear and thicken. It also takes a very long cook time–but it’s worth it!

Oils
24 ounces coconut oil
10 ounces olive oil
10 ounces castor oil
3 ounces jojoba oil

Lye Solution
11 ounces potassium hydroxide
33 ounces distilled water

Trace Time: 15 minutes
Cook Time: 6 hours
Dilution Rate: 20 percent
Neutralization: 33 percent borax solution, 1 1/2 tablespoons per pound finished paste
Sequestering Agent: sugar solution, 5 percent per pound diluted soap
Thickening: 2 ounces glycerin per pound of diluted soap
Scent: 3 percent fragrance or essential oil per pound diluted soap

Moisturizing Shampoo with Lanolin:

Notes: This one also resulted in an initially slightly cloudy soap due to the lanolin, but not as cloudy as with the jojoba in the previous recipe. You can clear it up with sequestering agents. Even at 20 percent, it wasn’t completely diluted. Rather than dilute further, I added a reduced measure (1 tablespoon per diluted soap weight) of the 33 percent borax solution. If you prefer to not do that, you may have to dilute to 15 percent and increase the thickener. Since I emulsified slightly with the borax solution, added neutralization wasn’t necessary. If you don’t emulsify, neutralize. This soap was clear immediately after adding the sugar solution, but required sequestering time to thicken.

Oils
24 ounces coconut oil
13 ounces olive oil
11 ounces castor oil
2 ounces liquid lanolin

Lye Solution
12 ounces potassium hydroxide
36 ounces distilled water

Trace Time: 13 minutes
Cook Time: 5 hours
Dilution Rate: 20 percent
Emulsification: 33 percent borax solution, 1 tablespoon per pound diluted soap weight
Sequestering Agents: sugar solution, 5 percent per pound diluted soap
Thickening: 2 ounces glycerin per pound diluted soap
Scent: 3 percent essential oil per pound diluted soap

All-Around Home Cleaning Soap:

Notes: This recipe is the easiest one to make. (It’s a good one to pick to practice on first.) It cooks relatively quickly and is clear immediately. I used the highest proportion of borax solution recommended for emulsifying so I didn’t have to dilute further than 25 percent. The high olive oil content in this soap would make dilution difficult even at 20 percent. Since borax is a detergent agent and I intended this soap for home cleaning, I went right ahead with lots of borax. No further neutralization or thickening was needed.

Oils
23 ounces coconut oil
25 ounces olive oil

Lye Solution
12 ounces potassium hydroxide
36 ounces distilled water

Trace Time: 15 minutes
Cook Time: 4 hours
Dilution Rate: 25 percent
Emulsification: 3 tablespoons of 33 percent borax solution per pound diluted soap
Scent: several drops fragrance or essential oil per pound diluted soap

For laundry, I use this at 1/3 cup per load and add some washing soda and baking soda with a splash of vinegar. (How much washing soda and baking soda per load is up to you. You can find per-load recommendations on the side of the boxes. I use less than the manufacturers recommend because I think they recommend too much.)

You can use it straight up for washing dishes in the sink. It cuts grease! For the dishwasher, fill your dishwasher cups almost completely with it and add a little borax for detergent power.

Resource List (not exhaustive, but will get you started)

Supplies:
Wellington Fragrance
Bramble Berry
Summer Bee
Soaper’s Choice

Discussion/Questions:
Yahoo Liquid Soapers
CITR Liquid Soapers

Calculators:
Summer Bee
Bramble Berry
Soap Calc

Also:
The Catherine Failor book: Making Natural Liquid Soaps
Lye Safety Review
All My Soapmaking Posts and Tutorials

Soap Math
If you have trouble with all this soapy math (I do), here’s a tip. If you want to figure ounces for anything that’s in pounds, change the pounds to ounces (multiply the pounds by 16). To find a percent of anything, move the decimal two places to the left and multiply it. 2% = .02. Pounds times 16 times the percent (in a decimal). For example, say you want to fragrance six pounds of liquid soap at two percent. What is two percent of six pounds? 6 times 16 equals 96, and 96 times .02 equals 1.92 ounces. You’d add 2 ounces of fragrance.

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Happy liquid soaping!

Update five years later: If you got this far without running away screaming, congratulations. If you want an easier method that doesn’t involve math, see how I make liquid soap now, the easy way, here.