Cold Process Liquid Soap (CPLS)

How I make coconut-based liquid soap

When I first started learning how to make cold process liquid soap, the information out there was scarce. Every answer felt scattered or incomplete. So I decided to document my own process in a clear, step-by-step way for anyone who might be searching the same way I once was. If you’re trying to learn CPLS and felt frustrated by the lack of guidance, this tutorial is exactly what I wished I had found.

Cold Process Liquid Soap, or CPLS, starts as a soap paste that’s later diluted into liquid form. The paste is made using potassium hydroxide (KOH) and allowed to gel and saponify with its own heat. It’s the same idea as cold process bar soap, just using KOH instead of sodium hydroxide (NaOH).

I originally made a pure coconut bar soap with no superfat that turned out to be the best dish soap I had ever used. That made me wonder why I couldn’t do the same thing in a liquid form. So I did.

Why Coconut Oil?

Coconut oil is naturally cleansing and can be drying on the skin, which is exactly what you want in a dish soap. Most soapmakers add superfat when using coconut oil, but for cleaning dishes, low or zero superfat is ideal. This soap can be used as a body soap if someone has oily skin, but I would not recommend it for dry skin.

Before we begin, I’m assuming you already know soapmaking safety. If you don’t, stop here until you do. KOH is no joke.

Gather Your Supplies

For this recipe, I added a few ingredients that I don’t use in my bar soap. Liquid soap behaves differently, and some additives help with clarity, viscosity, and dilution.

My formulation:
• Coconut oil 90 percent
• Castor oil 10 percent
• Sugar (1 tsp PPO)
• Sodium lactate (1 tsp PPO)
• KOH (potassium hydroxide)
• Distilled water (2:1 water to lye)
• A preservative safe for pH 8–9
• Essential or fragrance oils and liquid soap colorant (optional – not used in this tutorial)

With any recipe, run the formula through a soap calculator. I like Soapee. SoapMaker3 is also excellent, though I’ve found its defaults sometimes need adjusting for liquid soap.

Knowing how to calculate lye manually is a great skill and helps confirm your numbers. One wrong setting can ruin an entire batch.

Let’s Get Started

Measure Your Oils

Measure out your coconut oil and castor oil. I make my liquid soap paste in a small bucket with a lid. It keeps the paste airtight and easy to store. There’s no need to melt the coconut first unless you prefer to.

Measure Your Water and KOH

Measure your distilled water and set it aside.
Measure your KOH and set it aside as well.

Prep Your Additives

Get your sugar and sodium lactate ready so you don’t have to stop mid-process.

The sugar will be added while the lye water is still hot. Sodium lactate helps the paste dissolve more easily later on.

Mixing the Lye Solution

Slowly add your KOH into the distilled water and stir until completely dissolved.
Be careful; it heats up very fast.

Add the sugar next and stir until it melts completely.

Combine the Lye Solution with the Oils

Pour the lye water down the shaft of your stick blender to help prevent splashing. This is the safest method.

Blend until all the solid coconut oil melts. The mixture will cool a bit but will heat up again as saponification begins.

Blend and Rest Cycles

Stick blend for four minutes. Rest for ten to fifteen minutes.

The mixture may separate when it rests. This is normal and it blends back together easily.

Blend again. Rest again. You’ll notice it slowly thickening.

Blend for another four minutes, rest again.
Don’t hover over the bucket blending nonstop. That will only overheat your blender.

The batter continues to heat up on its own as the reaction moves along.

Eventually, the batter will seize to the point the stick blender can’t turn.
Switch to a spatula and stir until it becomes too thick to move.

Let It Gel

Once it reaches a thick paste, cover it tightly with plastic wrap and secure it. Let it sit undisturbed for eighteen to twenty-four hours while it completes gel phase.

Checking the Paste

After eighteen hours, your paste should look shiny and slightly translucent. That tells you it has heated internally and fully gelled.

Diluting the Paste

Take equal parts paste and hot distilled water and begin dissolving. This part requires patience. Liquid soap paste dissolves slowly.

Once fully dissolved, check the clarity.

The pH for liquid soap should be around nine. This batch was right on target.

Dilution and Adjustments

Since this is a coconut-based soap and I use it mostly for dishes, I do not add fragrance or color. I also do not dilute past a 1:1 ratio of water to paste. Coconut liquid soap tends to be thinner than other formulas, and I prefer how it behaves in foamer bottles.

Heat your distilled water and either pour it over the paste or add the paste to the water. Either method works. You can dilute all at once or in stages.

If you plan to scent your soap, remember some fragrances can cloud an otherwise clear batch.

Preservation and Bottling

Once the paste is fully dissolved, add your preservative according to the manufacturer’s instructions. Please don’t skip this step. Water-based products grow bacteria easily, and selling unpreserved liquid soap is unsafe.

Finished Cold Process Liquid Soap

I hope you enjoyed this step-by-step guide to making Cold Process Liquid Soap for dishes or oily skin. I enjoyed putting it together and hope it helps others who are curious about coconut-based CPLS.

In the future, I plan to write a blog on formulating your own liquid soap recipes, along with tips. Once that’s done, I’ll link it here.

Happy soaping!