How to Make Homemade Liquid Soap

Prepare the Lye-Water Solution

One major difference between making liquid soap and bar soap is that liquid soap is a "hot process" soap. Instead of relying on the heat generated by the saponification process, you add heat using a double boiler, oven, or slow cooker. The recipe below calls for a double boiler or oven, but a slow cooker is best. Slow cookers keep everything in one pot and let the ingredients cook evenly without having to monitor the water like in a double boiler. Take the following steps to mix the lye water for your liquid soap:

• Measure your oils and put them in the slow cooker on low. You want this mixture to stay at about 160 degrees Fahrenheit (give or take 10 degrees).
• While the oils are heating up, mix your lye water using the standard lye-making procedure. If you've never used potassium hydroxide before, don't be alarmed. It's a bit more volatile in the water than sodium hydroxide and makes an odd boiling or groaning sound as it's dissolving. This is normal.
• When the lye water is completely mixed and clear, slowly add it to your oils (you don't need to wait until it is cool). Don't turn the stick blender on yet. Simply stir the oils and lye together. Then, like in cold-process soapmaking, start using the stick blender. At first, the mixture will seem like it wants to separate, but keep blending.

Bring the Soap Paste to Trace

Depending on your mixture of oils, it may take a long time to get to trace, possibly up to 30 minutes. "Trace" for liquid soap looks much like it does during cold-process soap making; it's somewhat ​pudding-like, or more like a blend of pudding and applesauce with the characteristic "traces" or ridges that occur when you dribble the soap back into the pot or stir. You can't over-stir the mixture, so ensure you have a solid trace before moving to the next step.

Cook the Paste

Once the soap has reached trace, you'll need to give the mixture one more good stir, shake off your stick blender, put the lid on the pot, and wait. Check on the soap in about 15 to 20 minutes. If there's any separation, stir the mixture and put the lid back on. Keep checking on the soap every 20 to 30 minutes.

The mixture will transform through several stages in the three to four hours it takes for this soap to cook. Don't worry if you don't see one of the phases. Sometimes a stage will be brief and you'll miss it. The six stages usually look like the following:

1. Thick applesauce
2. Cooked custard with small bubbles
3. Watery mashed potatoes
4. Solid taffy
5. Chunky/creamy petroleum jelly
6. Translucent petroleum jelly

Keep stirring every 30 minutes or so through each of the stages. It'll be difficult to stir through the taffy stage; do the best you can. A potato masher will help break up the taffy-like substance. The soap will become creamy and move into the translucent petroleum jelly stage right about the moment you think it will never finish cooking,

Test the Paste

Once you've reached the three- to four-hour mark, the soap will have softened and turned translucent. At this point, you'll need to time the soap to see if it's cooked long enough. Take these steps to test:

• Take 2 ounces of boiling water in a separate bowl and add in one ounce of your soap paste.
• Stir the soap, breaking it up and helping it dissolve in the water. Once it's completely dissolved (several minutes) check to see how clear it is.
• If the mixture is lightly cloudy, that is a good sign that the soap is ready. The soap will "settle" after it's finished and become much clearer.
• If the dissolved soap mixture is milky or very cloudy, it may need more cooking.

Dilute the Paste

If the test mixture stays clear as it cools, you can continue. The last measure of patience is needed when taking these steps to dilute the paste:

• Take the remaining 40 ounces of distilled water and bring it to a boil.
• Add the water to the soap paste. Stir it in a bit with a spoon or the potato masher.
• Turn the heat off on the slow cooker. Put the lid on and wait for about an hour.
• After an hour or so, stir the mixture some more. It should have softened a bit by now. It will likely be very chunky and gooey.
• Put the lid back on and leave the mixture overnight to further dissolve, or continue to stir every hour or so.

Neutralize the Liquid Soap

After the soap paste has completely dissolved in the water, it's time to neutralize the soap and add your fragrance. Take the following steps:

• Turn the slow cooker back on and bring the mixture back up to 180 degrees Fahrenheit or so.
• In a separate container, mix the neutralizing solution. You can make either a 20 percent solution of boric acid or a 33 percent solution of 20 Mule Team Borax. For the boric acid, take 8 ounces of boiling water and add 2 ounces of boric acid. For the Borax, use 3 ounces of Borax in 6 ounces of boiling water. It's important to stir well and make sure that the mixture stays hot. As this mixture cools, the Borax or boric acid will start to precipitate out of the mixture and it won't mix into your soap.
• Add about 3/4 of an ounce of neutralizer for every pound of soap paste (just the paste, not the added water.) For this recipe, which has about 2.8 pounds of paste, add 2 ounces of neutralizer solution. Using too much neutralizer (especially the boric acid solution) can cause cloudiness, so it's best to round down how much neutralizer you add by erring on the conservative side.
• Slowly pour the neutralizer into the re-heated soap mixture and stir well. Add one ounce first and let it sit for a bit. Then add another half ounce. If it remains clear and does not become cloudy, add the final half ounce.

Add Fragrance or Color

After neutralizing the soap, and while it's still hot, add fragrance and color. A good rule of thumb is to fragrance liquid soaps at about two percent to three percent. For example, this recipe will call for about three ounces of fragrance. Add the fragrance to the soap and stir it in well.

If adding color, put in a few drops at a time and stir well. Remember to take into consideration the amber color of the soap base while you're adding color.

Let the Liquid Soap Rest

It's time to let the soap cool. Pour the soap into large bottles or jars. Put the bottles or jars aside in a cool place to let the soap rest. During this resting phase, the insoluble particles should settle to the bottom and any minor cloudiness caused by insoluble particles in the oils or added fragrance oils should clear up. The soap will need to settle for one week. When you are pouring your soap into their final bottles or tubes, be extra careful not to disturb the settled solids.

Enjoy Your Homemade Liquid Soap

Congratulations, you've entered the advanced world of liquid soap making. There are nearly as many recipes and variations with liquid soaps as there are with bar soaps. Though there are no preservatives, homemade liquid soap potentially has a longer shelf life than bar soap because of the difference in oil content. However, different oils and techniques will result in varying products, from liquid soap to shampoo to shower gel.