two liquid soaps

Easy & Quick Tips for Making Liquid Soap Successfully

guest contributors soap science and info

This article comes to you courtesy of Molly.

When soapmakers jump into making liquid soap, they often have trouble with the process because it's quite different from bar soapmaking! Boundaries cannot be pushed in liquid soapmaking as easily as in cold process or hot process soapmaking, but there are certain tips and tricks that can help you make awesome liquid soap!

I typically write articles in my head for a few days before I am ready to sit down and start typing it up. This article, however, has been an ongoing conversation with myself for months! Why has it taken so long? Every time I think I am ready to go, I learn something new about liquid soapmaking!

Why Would You Want to Make Liquid Soap?

Before I get into the tips and tricks I have picked up in my liquid soapmaking journey, let's talk for a minute about why you might want to add some liquid soap to your product line up:

Liquid soap has better margins than bar soap.

Liquid soap is profitable, no matter how you look at it. Even taking into the account the cost of liquid soap packaging (a bottle & pump), you can make more money selling liquid soap then you can selling bar soap.  Many consumers consider liquid soap a higher end item and will pay more for the convenience and look of liquid soap. Plus, the cost of goods sold when making liquid soap is lower (a much higher percentage of liquid soap is distilled water compared to bar soap).

Millennials prefer liquid soap over bar soap.

I have read quite a few articles that say young adults prefer liquid soap and bodywash over bar soap.  While I'm personally a fan of bar soap, when you are in business, you have to cater to what your target market wants. Even if your target is older than millennials, eventually that may change as time passes or you may find that your target market also enjoys the convenience of liquid soap.

Liquid soap is the perfect product for a guest bathroom.

There is a big market for paired liquid soap and lotion sets for the guest bathroom and the kitchen. Even bar soap lovers like me understand that this set is a more elegant solution for entertaining!

 Ridgeway Soapworks Liquid Soap & Lotion Set

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 .

Shortly after I started making bar soap, I bought Catherine Failor's Making Natural Liquid Soaps book and read it cover to cover. I was so intimidated that it was nearly a year before I attempted my first batch!

While there is a lot of great information in Failor's book, I highly recommend Liquid Soapmaking by Jackie Thompson instead. I am a bit of a soaping rebel and like to test the limits of "rules" that I read about.  I have had a lot of failed batches because of that, which is fine (but frustrating). However, whenever I follow Jackie's process and recipes exactly as written, the soap comes out perfectly.

My first batch of liquid soap was a liquid glycerin castile soap recipe I found on a popular YouTube channel.  While my batch of liquid soap came out ok, it had a high superfat which can cause problems. (Using glycerin in place of the water in the lye solution will also cause long-term stability issues!)  I will explain the superfat issue shortly but I caution you against starting with complicated recipes. If you want to learn how to make liquid soap, Jackie's recipes are easy to follow and well-tested.

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!

 Finished soap paste is typically thick and semi-translucent. The next steps are dilution, adjustments, and scent/color!

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!

You can use two methods to determine if your liquid soap has excess oil or lye:

To check for excess oil, mix a small bit of your fully cooked paste with distilled water. If is is NOT milky, then your oils are saponified.  Cloudy is ok, milky is NOT. If your soap has unsaponified oils, you can add some dissolved KOH solution to saponify the extra oils.

To test for excess lye, you can use phenolphthalein drops in your diluted paste.  Phenolphthalein drops test a solution for a small range of pH, turning light pink to dark magenta if the solution has a pH between 8 and 9.8.

If you add a drop of phenolphthalein to your liquid soap and it turns pink, you have excess lye. Adding dissolved citric acid is one method you can use to neutralize it, or using stearic acid is another. Both methods and measurements for them are covered in detail in Jackie's book. If the diluted liquid soap does not turn pink when phenolphthalein drops are added, you are good to go!

 Phenolphthalein drops can be used to test diluted liquid soap for excess lye.

Tip: Test your fragrance before adding it to your whole batch of liquid soap.

The last step before bottling your liquid soap is to add fragrance (if desired). Be prepared for different fragrance oils and essential oils to react with your liquid soap! It's always a good idea to test your fragrance in a small sample of your liquid soap for at least twenty four hours. Some fragrances cause clouding, separation, thickening, or even, thinning. I highly suggest you test a small amount of finished liquid soap with your fragrance before you add it to your entire batch.

Tip: Find like-minded people and don't be afraid to get help.

Another great way to learn about this method of soapmaking is to join any of the liquid soapmaking Facebook groups! There are people far more knowledgeable in them than myself, and the files are rich with information.  And sometimes, Jackie Thompson herself will comment on questions and requests for troubleshooting.

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