DIY Liquid Soap in a Slow Cooker

1 / 2
Handmade liquid soap is similar to the soap you would buy in a store, except you can customize the colors and smells to fit your home.
2 / 2
“DIY Artisanal Soaps” by Alicia Grosso guides you step-by-step through the home soapmaking process, from basic recipes to packaging and selling your creations.

DIY Artisanal Soaps (Adams Media, 2016), by Alicia Grosso equips readers with everything they need to begin making their own beautiful soaps right at home. Grosso lists the main ingredients needed, plus recipes on how to personalize your soaps to be perfect for your home. In this excerpt, she gives her recipe for making liquid soap in a slow cooker.

For this recipe, use a 3 1/2-quart slow cooker. If you use too small a slow cooker for the batch, you increase the chances of overheating, overflowing, and the “volcano” action of the cooking soap. You can make liquid soap in a double boiler or with the oven hot-process techniques, too.

This recipe yields about 3 pounds of paste, which will dilute to about 6 pounds of liquid soap.


• 22 ounces coconut oil
• 4 ounces castor oil
• 1 ounce jojoba oil
• 16 ounces water
• 6 1/4 ounces potassium
• hydroxide
• Rubbing alcohol in small spray
• bottle to control bubbles


1. Set the slow cooker to high. Place the coconut oil, castor oil, and jojoba oil into the slow cooker. Cover to hold in heat. Melt the oils.

2. Place the water in a heatproof container and sprinkle the potassium hydroxide into the water. Stir until all the potassium hydroxide is dissolved. (This mixture won’t get as hot as the lye solutions for solid soap since you’re using more water.) Without waiting for it to cool, add the potassiumwater solution to the oils by pouring it in a thin stream, stirring constantly and carefully to fully combine the mixture.

3. Using an immersion blender, blend the mixture to trace. Keep the head of the blender fully immersed to avoid blending air into the soap batter.

4. When the mass starts to thicken, the mixture will thicken fast—it may just become nearly solid! Remember that this will happen all of a sudden, so watch that you don’t burn out the blender by not paying attention.

5. Let the paste cook until it’s translucent. (This will take about 3 hours.) Stir the neutralizing soap every 30 minutes by folding the soap with a firm yet careful hand, incorporating the puffy areas into the center. (Keep the slow cooker covered as much as possible. The longer you leave the lid off, the more water will evaporate, which will throw the formula out of balance.)

6. After 3 hours, test to see if the soap is neutral. Scrape a small portion onto a folded-up paper towel. Drip a couple of drops of phenolphthalein onto the soap. If it turns bright pink, it needs more cooking. If it is clear with just a little pink, you’re ready to move on.

7. If you’re going to make finished liquid soap right away, measure out the amount you want to dilute and store the rest. Take the finished paste out of the slow cooker and let it cool in a glass or metal bowl. When it’s cool, put the amount you wish to store into a heavy zip-lock bag.

8. Place the paste that you wish to make into liquid soap in a stainless steel pan over direct heat on your stove, to melt the paste into the water. Use equal parts paste and water. Although it will produce some foam, boiling is the best way to get it started. Be sure the pan is an appropriate size for the batch you are making. One pound of paste and 2 pounds of water will fit perfectly in a standard 4-quart saucepan.

9. Bring the paste and water to a boil. Reduce the heat and simmer, uncovered, for 15–30 minutes. You need to stay with it, making absolutely sure it doesn’t boil dry. It may be tempting to put a lid on, but it is better to leave the lid off, because the boil-over potential is very great, even if you keep the heat the same.

10. When the soap paste has dissolved, remove the pan from the stove and stir to incorporate as much foam as you can.

11. Spritz the surface with rubbing alcohol to clear any bubbles that remain. (Do not do this near a gas range!) Add color and fragrance, if you like.

If you’ve used sodium hydroxide, you’ll notice that this stir to trace is different. It is very opaque and milky right away, yet very thin. You have to use the hand blender for action to get it to start tracing. When it does, it happens all of a sudden. Big bubbles will start to kick up when it’s about to firm up.

You can divide the finished soap into small amounts and experiment with color and scent. Some fragrance oils and essential oils have color of their own, so add them before you add the colorant. Liquid food colors work perfectly well and look best when used in small amounts. The liquid soap will be somewhat yellow, so remember this when working out your color plan.

Homemade liquid hand and body soap is similar to the kind you buy at the store. You can pump or squeeze it in a similar way, and it foams nicely on the skin, especially if you use a sponge or a loofah. Where most liquid soaps made at home fall short is if you try to use them for shampoo, shower gel, or bubble bath.

Of course, you can use the recipe as shampoo to see how you like it. Many people prefer the feeling they get from a detergent shampoo to the feel of handmade liquid soap shampoo. You may find, though, that you love it! Handmade liquid shampoo can leave some people’s hair feeling oily, stiff, dry, or just strange.

All shampoo will eventually leave a buildup on your hair, and homemade soap will do this faster. It is a good idea to use a vinegar rinse at least once a week to take care of this. You can make wonderful herbal vinegars that you’ll use highly diluted in water. Infuse 2 cups of white or apple cider vinegar with ¼ cup dried lavender, rosemary, or other herb of your choice. Let it infuse for a week. Use 1 tablespoon of strained, infused vinegar for each 8 ounces of water. You can put this in a big squeeze bottle when you know you’re going to need it and keep it in the shower. Use up the diluted solution within a few days.

You can try making bubble bath with the liquid soap, too. To get better bubbles, try adding 1–3 teaspoons of glycerin per pound of diluted soap. Depending on the water in your area, this may or not produce big bubbles.

Using Foaming Bases

If you want to make your own shampoo, shower gel, and bubble bath, you can buy clear, unscented shampoo, shower gel, and bubble bath. These premade bases are technically not soap, but they are used for cleansing, they bubble, and they present opportunities for creativity. You warm them and make additions, but instead of pouring them into molds like you would with casting soap, you pour them into plastic bottles. A lineup of beautifully colored and scented shampoo, shower gel, and bubble bath can look like shiny jewels on the edge of the tub. Think about how you can create coordinating looks for your bathrooms, coded colors for each type of product, or even each family member.

If you want to choose one base to use universally, choose a shampoo base, as you can certainly use that as a body wash, and often as a bubble bath, although you have to try each one as they differ in how well they hold up in the bath.

Choosing a Container

Transparent, squeezable plastic bottles that are made of PET plastic are ideal. The kind of plastic is important, because there are many plastics that will not stand up to fragrance oils or essential oils. Look for the initials PET on the bottom of the bottles if you reuse bottles you already have, or buy them at the drug store. If you order from an online soapmaking supplier, look in the product descriptions to be sure you get PET. Get PET bottles even if you don’t intend to use scent material, because chances are, you will eventually.

Foaming Bases and Detergents

Foaming bases are primarily water, detergents, surfactants, and skin or hair conditioners. Detergents are commonly derived from coconut, palm, and olive oils, or the separated fatty acids of those oils. You’ll often find fatty acids, such as sodium lauryl sulfate, at the top of the list of ingredients in shampoo, bubble bath, and dishwashing liquid.

Two- and 4-ounce bottles are excellent choices, especially when you are first starting, because you aren’t committed to a large amount of any one experiment. For most foaming bases, flip-tops are perfect. You can also get pumps, and they are usually more useful for 8- and 16-ounce bottles (they can topple the smaller bottles). Most packaging suppliers sell bottles and caps separately, so be sure to order both. Two favorite bottle shapes are called Boston Round and Cosmo Oval. It is partly a matter of aesthetic preference, but the Cosmo Ovals are easier to squeeze.

Adding Colors and Scents

Like so much in soapmaking, your options with foaming bases are virtually unlimited. You can add color, fragrance, and other additives. You can choose sheer colors; shimmery, pearly micas; and even glitter. The crystal-clear appearance of unscented liquid bases can be accented beautifully with just about any kind of cosmetic colorant. Gel color, Lab Colors, mica, mineral pigment, and food coloring from the grocery store are all great choices. Start with a small amount of color and work your way up. Keeping it relatively sheer takes advantage of the way light passes through the liquid.

Aromas from fragrance oils are wildly varied, and you can decide how strong or how light you want the scent to be. Using essential oils and other natural aromas, you can create truly aromatherapeutic products for you to use daily and as need arises. Most bases will take any cosmetic fragrance material: fragrance oils, essential oils, or blends of both. Some suppliers suggest the use of a solubulizer to hold the scent material in suspension and keep it from making the base cloudy or runny. Whether you need it or not depends on the kind of base and the kind and quantity of fragrance material. Get a small bottle when you order your base and scents; that way you’ll have it if you need it, and if you don’t you won’t have a large amount of something you don’t need.

Other things you could add to your foaming base include scrubs like bamboo granules and powdered loofah, jojoba spheres, and clays that add color, scent, and texture. Additionally, you can add the foaming bases to basic handmade beauty formulas, such as sugar scrubs, to add foam and rinsability.

More from: DIY Artisanal Soap

DIY Basic Cold Process Soap
Making Homemade Laundry Soap
Using Colors in Homemade Hand Soaps

Excerpted from DIY Artisanal Soaps: Make Your Own Custom, Handcrafted Soaps! by Alicia Grosso. Copyright © 2016 Adams Media, a division of Simon and Schuster, Inc. Used by permission of the publisher. All rights reserved. Interior images ©