How to Make Liquid Soap From Bars of Soap and Castile Soap

How-To Guides
by How-To Guides

By Sharon Brandwein

Whether you're looking to stretch a dollar or just want to try out a DIY project, try your hand at making your own liquid soap! We'll be honest: Making liquid soap completely from scratch is an intensive process that involves a hoard of materials that the average DIYer likely doesn't have on hand. But luckily, you can learn how to make your own liquid soap with a few soap-based ingredients you likely already have or can find on the shelf of a store.

Our guide will walk you through how to make liquid soap from Castile soap and how to make liquid soap from bars of soap (perfect for those slippery odds and ends that you'd end up throwing in the trash anyway!). Here's how to make liquid soap yourself.

hand holding brown bottle of soap covered in bubbles

Photo via Amanda C, Hometalk Team

How to Make Liquid Soap From Castile Soap 

One way to make liquid soap at home is to use Castile soap, which is readily available in any local grocery store or online. Castile soap is a natural surfactant, so it’s great for making your own liquid soap. If you use Castile soap for this DIY, it’s worth noting that the more Castile soap you use, the more suds you’ll have in your liquid soap. However, it’s also worth noting that suds are not an indicator of cleaning power—they’re really just a visible cue to put us at ease that the soap is doing its job.

The recipe below is a basic liquid soap recipe, but you can tweak it to your heart’s content. For example, feel free to experiment with the essential oils. Lavender, lemon, and orange are always good options for soap, as they smell clean and fresh.

Tools and Materials Needed

  • Reusable soap dispenser
  • 2 ½ cups water
  • ⅛ cup Castile soap
  • 10-15 drops of essential oil 

Step 1: Fill the Dispenser with Water

Begin making your liquid soap by filling the reusable soap dispenser with 2 ½ cups of water.

Step 2: Add the Castile Soap

Next, add the castile soap to the water. 

Step 3: Add the Essential Oils 

Finish up by adding a few drops of your favorite essential oil. Give the bottle a good shake to mix the ingredients together. 

Make It Moisturizing

If you’d like to make a moisturizing liquid soap, you can add a few drops of vitamin E oil or coconut oil to the mix. Sweet almond, oil olive oil, or jojoba oil are nice moisturizing options as well.

How to Make Liquid Soap from a Bar of Soap 

If you find yourself with small bits of bars of soap that aren’t much help in the shower, you could use the leftover pieces to make liquid soap. This is a relatively easy process that helps you use something you may otherwise throw away. 

Tools and Materials Needed

  • Small saucepan/pot
  • 3 cups of water
  • ½ cup of bar soap chopped into small pieces
  • Stirring utensil
  • 1½ teaspoon of glycerin
  • Natural preservative
  • Essential oils (optional; if your soap already has a scent, you can probably skip this ingredient)
  • Soap dispenser

Step 1: Heat the Water 

Add the water to the saucepan and place the pan on your stove with the temperature set to medium/high.

Step 2: Add the Chopped Soap 

Add your chopped bar soap to the water and let it simmer until it’s completely dissolved.

Step 3: Add the Glycerin and Preservative

Once the bar of soap is completely dissolved, remove the pot from the stove and add the glycerin, the natural preservative, and a few drops of any essential oils you're using. Stir.

Step 4: Stir and Transfer

In the morning, give the soap a good stir to thoroughly mix the ingredients and then pour it into your soap dispenser. 

Grate the Soap

While the recipe indicates that you should chop the bar of soap up into little pieces, you can also use a grater to expedite the dissolution process. Also, if your soap is too thick to cut or grate, you can always add some water to thin it out a bit.

hand holding spoon with bronze bowl and vegetable glycerin in background

Photo via Amanda C, Hometalk Team

FAQs About How to Make Liquid Soap

Is Glycerine Necessary for Making Liquid Soap? 

Glycerine isn’t necessary per se, but adding it to your liquid soap will yield a nicer end result. The glycerine will keep your soap from clumping, it will impart a creamy texture to your soap, and it also has a moisturizing effect that bar soap often lacks.

Some Castile soaps will have the glycerin distilled out of them, but some, like Dr. Bronner’s Castile soap, retain the glycerine. If you’re using a different brand to make liquid soap from Castile soap, read the ingredient list and adjust your recipe accordingly. A good rule of thumb is to add a teaspoon of glycerin for every 3 cups of water to your liquid soap.

Do I Need to Add Preservatives to Liquid Soap? 

Any DIY skincare recipe that includes water should also include a preservative to prevent mold and bacteria from growing in the product. If you’re using a bar of soap to make liquid soap, you will need to add a preservative. If you’re using castile soap to make your own liquid soap, that already has preservatives in it, so you can skip it.


Do you have any unique recipes for making liquid soap? Tell us in the comments, we’d love to know!

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