How To Make Liquid Soap
The Process for Making Liquid Soap
There are a few methods to make liquid soap, but the most common method is to make a soap paste using the hot process method. The soap paste looks a lot like hot process bar soap that has not yet hardened. The primary difference between liquid soap and bar soaps is that potassium hydroxide (KOH) is used in place of sodium hydroxide (NaOH) for the lye solution.
There are some other differences between the two processes, which I will cover further down. Once you make the paste for liquid soap, you dilute the paste with water or another liquid. Then, you can add any scent or color that you would like and voila! You have liquid soap!
- Blending the oils and lye solution for making liquid soap
- When making liquid soap, trace is similar to bar soap but thicker!
- Liquid soap is typically cooked with a hot process method, and is very thick (as shown).
Tips for Making Liquid Soap
Here are some of the things I’ve learned over the last year of making liquid soap, so you won’t have to learn them the hard way:
Tip: You cannot superfat liquid soap to the same degree that you can with bar soap.
The max you can superfat liquid soap is around 3%. However, a 3% superfat is actually very high if you want to add a scent! I have learned this lesson over and over because I was sure there must be a way to make a 8% superfat liquid soap. Unfortunately, my customers like scented soaps, and when you add either essential oils or fragrance oils to a highly superfatted soap, it separates. (And it looks very unappealing when that happens.)
Tip: Some oils are more suited for making liquid soap than others.
The most common oils used in liquid soapmaking are olive oil, coconut oil and castor oil. I recommend your first recipe is one from Jackie’s book using those three oils.
Coconut oil helps the liquid soap paste saponify, plus it adds that lather boost you know it for. Other oils that are high in saturated fatty acids like tallow, cocoa butter, shea butter and lard present challenges (mainly, cloudiness) in liquid soap that you may want to tackle down the road, if you want to use them.
Olive oil helps keep the liquid soap thicker, while also being moisturizing, and castor oil works it’s magic in liquid soap (just like it does in bar soap)!
Tip: Most liquid soaps are thinner than what you may expect.
Most of the liquid soaps we encounter commercially are actually surfactant-based products, and not actual soap. Olive oil based liquid soaps will be thicker than coconut oil based liquid soaps, so you’ll want to keep that in mind when using different recipes.
If you decide to make a 100% coconut liquid soap for dishwashing or cleaning, it will be water-thin. If you want to thicken it, you will need to add a thickener of some kind. Adding a thickener is not the end of the world, but a lesson many people learn the hard way!
Tip: Liquid soapmaking requires patience!
I am a hot process soapmaker, so I am used to starting and finishing a batch of soap FAST! But the dilution process in liquid soap works best when you give it time. Be prepared for this and don’t rush it!
It is easier in the long run to add a little water a time to dilute than it is to deal with a liquid soap that has too much water added. So add your dilution water slowly, give it time, and be patient.
Tip: Some additives can cause problems when making liquid soap.
A popular way to make liquid soap thicker is to use brine in place of your water in your lye solution. Like other additives and changes in traditional liquid soapmaking, this method has drawbacks. The biggest issue is that using brine in your lye solution can cloud the liquid soap. It also has the possibility of inhibiting lather.
Tip: Making lye solution with KOH is definitely different than NaOH.
Potassium hydroxide (KOH) does not generate as much heat as sodium hydroxide (NaOH) does, so your lye water will cool more quickly with KOH. You also want to make sure to stir when you add the KOH to the water to help it dissolve. Heads up: making a lye solution with KOH also makes a crackling sound that surprised me the first time!
Tip: Be careful of diluting your soap paste with anything other than distilled water.
I am specifically referring to what is called “bug food”. Goat milk, clays and other botanicals in liquid soap can create a breeding ground for mold and bacteria. Even if you choose to add a preservative, some of those additives will test the limits of what a preservative can do. Better safe than sorry!
If you make a liquid soap with a low to no superfat, and only dilute with distilled water, you should not need a preservative. Be sure to use good manufacturing practices (GMP) to ensure your products and containers do not get contaminated, though.
Tip: Liquid soap almost always needs to be tested and adjusted.
Potassium hydroxide (KOH) is not as pure as sodium hydroxide (NaOH), and it breaks down more quickly. Even if you are meticulous about measuring your ingredients, you may end with a soap that is either lye heavy or superfatted. One of the cool things about liquid soap is that both of those problems are easy to fix after your liquid soap is diluted!