Here is a question I get every so often, “Why doesn’t handmade soap lather?” When I explain that it does, the next statement inevitably follows…
“What makes soap lather?” This question has two answers: 1.) Using oils such as coconut or castor oil help – as does adding sugar. 2.) From a more scientific perspective, it comes down to the surface tension between the soap and water. Bubbles form as the result of air trapped in a thin film resulting from soap and water mixing. As the air displaces water molecules, surface tension is released. Lather is the result of lots of bubbles jammed tightly together.
Why Lather Matters in Soap
Soap is something that we use every day, but we never really think about how it works. No matter what kind of soap or even shampoo that is being used, it is almost intuitive to create a lather before washing.
It feels good and gives the impression that the bubbles remove dirt. Soap does not really work that way. But 20 years of “Scrubbing Bubbles” commercials have taken their toll on us all.
More importantly, lather is what people look for in quality soap. As mentioned, it feels good. It also helps us visualize where we have already washed. In our minds, lather paints the areas washed.
The Secret to Big Soap Bubbles
Don’t tell anyone, but I have a secret.
Most store-bought “soap” is not real soap. I know it sounds crazy but it’s true. Most bars bought in grocery and department stores are “bath and beauty bars”, “cleaning bars” and the like. They do not meet the definition of true soap as laid out by the FDA.
This is because they’re made with cheap chemical detergents instead of the all-natural glycerin you get from homemade soap. This is how they get the big bubbly lather.
Real soap produces lather, but the bubbles are typically smaller and the overall feel can best be described as creamy. For the most part, that is.
There are plenty of ways to increase lather naturally and even get some larger bubbles. Try these…
How to Increase Lather in Homemade Soap
There are several ways to increase lather in handmade soap without resorting to the use of detergents and artificial chemicals.
Let’s take a look at some of the most common solutions…
Use Oils with High Lathering Properties
Choosing the right oils is a great natural way to increase lather in soap while avowing the addition of chemical detergents. Some or the oils that contribute to better lather include the following, but for much different reasons:
Lather Producers
I have found most lather producers tend to be the harder oils or fats (when at room temperature). Different soap makers have different experiences and I am no different. I asked around my community of soaper friends and we all agreed on the following, to varying degrees:
Coconut Oil: Working with coconut oil is one of the best ways to increase lather in natural soap. But it’s also a balancing act because coconut oil can tighten skin and make it feel dry if moisturing oils are not added into the mix.
When combined with olive oil, sunflower oil, castor oil and shea butter it produces a wonderfully moisturizing bar that lathers well. This is true even though olive oil is not a lather rich oil.
Beef Tallow: Animal fat derived from beef animals, tallow is a super hard fat that lathers well. It lathers especially well when the amount of superfat is minimized to 5% or less.
Lard: Pig or hog fat is known as lard. It was the most common base fat for homemade soap in the United States and most of Europe until plant oils became more accessible and affordable. It lathers especially well with just a touch of sugar added to the recipe.
Almond Oil: This is not a hard oil but does the trick. It works best in small to moderate amounts when being used to improve a bar’s lathering properties.
Palm Oil: Palm oil is solid at room temperature but melts to a thin liquid and blends well with other oils. It works well to help build lather naturally in true soap (aka real soap).
Heads up!
There is some controversy around palm oil – not as a health risk but in how it is often harvested. If you want to make soap for sale, that uses palm oil, consider purchasing sustainable palm oil. It will cost a bit more but helps the environment and those who inhabit parts of the word where palm oil is harvested.
I am a big believer in helping people earn fair wages and protecting the environment when possible. A lot of soap buyers are as well and don’t mind spending an extra fifty cents on a soap bar if it will help. There is even a non-profit organization specifically created for ensuring the sustainability of palm oil – Roundtable on Sustainable Palm Oil.
Note:
Before we move on, it is important to note that the combination of oils is just as important when considering lather building properties. Single oil soaps typically do not lather well.
Lather Sustainer
Sunflower Oil: Sunflower oil does not do much to enhance the size of lather. However, it does help sustain lather on the skin for longer periods of time. It also helps keep the thin film that forms between soap and water stable. This thin film becomes bubbles when air is trapped.
Lather Enhancer
Castor Oil: Use small amounts of castor oil in combination with other oils to promote lather. Castor oil on its own will not lather well. But when it interacts with coconut oil it boosts gives it a slight kick.
When adding castor oil, I start with 5% as the minimum. Anything below that and I don’t feel enough difference in the final bar. The maximum I add is 10% of the oil quantity of the recipe.
It might not seem like a lot, but I have found anything much above 10% does not help with enriching lather. By the time you hit about 13% the bar can start to feel a bit tacky to the touch.
Avoid Too Much of Lather Reducing Oils
Olive Oil: When olive oil is the primary ingredient with a bar that has coconut oil as its secondary ingredient, it usually lathers nicely. Add some sunflower oil, a bit of shea butter and a dash of sugar and you have a lather powerhouse.
However, when a bar is made 100% from olive oil (Castile soap), or nearly so, it tends not to lather well.
Integrate Up to 7% Butter for Richer, Creamier Lather
Inserting a small amount of certain butters can help make real soap lather better. But I do mean small amounts. I try to stay at 5% max for shea and 7% for cocoa butter. This small amount adds just enough kick to “fluff” the lather up slightly, raising the soap bubbles on a thick creamy base.
This is not to say you cannot add more and get great results. You just need to be very familiar with the properties of all of the oils you are working with. The 5% and 7% ratios are what work best for me with most oil combinations.
When too much butter is added, it often overtakes the bar’s natural tendency to produce lather by not allowing the bubbles to get enough trapped air to fully form. In other words, the lather gets richer and creamier but seems lower because of the tiny bubble size. There are actually more bubbles, and more lather. The lather is just so fine it appears to be less.
Shea butter and cocoa butter work well in small amounts – especially when used in soap bases with high-lathering oils such as coconut, sunflower and castor oils.
Add Sugar to Bubble Up
Sugar helps increase lather and acts as a natural exfoliant. You don’t want to add in so much that you create a sugar scrub, but about ½ teaspoon per 4-ounce bar usually works well. That’s one tablespoon of sugar for every 24 ounces of oils used in your loaf.
Reduce the Superfat Amount to Increase Lather
Superfatting is when you intentionally leave extra oil in the soap knowing there is not enough lye solution to make it saponify and turn to soap. I generally superfat most soaps at about 5% because the added oils help moisturize the skin and it provides a safety margin.
By safety margin, I mean the recipe is not so tight that I have to worry about having too much lye in my soap. Superfatting means not enough lye. As long as it’s not too much, this just means a gentler bar. Too much lye can cause ski irritation and burning. That’s a very bad thing to be avoided at all costs.
Add Clay – Just a Touch
The tiny particulates in clay add to the friction that occurs between the soap, water, and your skin. This helps build lather – when done in the right (small) amounts. One or two teaspoons per pound of oil work well for my needs.
The whole friction thing is explained in detail in “The Science Behind Soap Lather” in just a moment.
The Exception to the Measuring Rule
Keep in mind, we (almost) always deal in weigh measures when making soap. Small amounts of dry powdery substances are the main exception – aside from lye which should always be weighed.
Just remember that it takes 3 teaspoons to equal 1 tablespoon and measuring clay and sugar into your soap will be easy.
Combine High Lather Options into Great Soap One Recipe
The best way to maximize lather in your homemade soap is to combine several of the high lather options outlined above. For example, you might start by:
- Combining coconut oil, palm oil, sunflower oil, and a bit of shea butter.
- Keeping the superfat level low (the free oil that did not saponify in the soap making process).
- Adding a small amount of bentonite or other clay.
- Using a high-sugar beer, red wine or even grape juice, instead of water, as the liquid for your lye solution. Just eliminate any carbonation and alcohol before adding in your lye to avoid a boiling hot eruption of lye solution.
The Science Behind Soap lather
The creation of lather all goes back to the basic chemical properties of water. Things are about to get deep and nerdy so hold on tight!
What Do You Know About H2O
As you might already know, water is compounded of two hydrogen atoms and one oxygen atom. When these molecules are pulled together within water, they create a thin layer, which is surface tension. Surface tension is defined as a measure of the force necessary to stretch or break the surface of a liquid.
Surfa-what was that?
Regarding soap, soap is a natural surfactant. A surfactant is used to reduce that surface tension of the water. If there is not a surfactant, the water will continue to hold on to itself due to the water molecules being surrounded by and attracted to other water molecules. Therefore, to allow water to spread out over a surface, a surfactant is required.
Soap Chemical Breakdown
Now, let’s discuss the chemical properties of soap. Soap molecules have two different ends: the hydrophilic end is the end that likes to stick to water, and the hydrophobic end likes to repel water.
As the soap molecule acts as a connecting bridge, the hydrophilic end attaches to a water molecule and the hydrophobic end attaches to either a dirt or oil molecule. Once soap is mixed with water, another chemical reaction occurs to create the lather.
Soap and Water DO Mix!
Upon mixing water and soap, thin sheets are created where a thin layer of water molecules is put in between two layers of soap molecules. As mentioned before, the hydrophilic and hydrophobic ends are placed accordingly in this position, with the hydrophilic ends pointed toward the water and the hydrophobic ends pointed toward the oil or dirt.
Lather Needs Friction
In order to create the lather, friction also must occur. By rubbing a bar of soap over wet skin or a cloth, this is the friction that is needed, which is also creating tiny air bubbles on the surface of the soap.
Because hydrophobic ends are water repelling, they attach themselves to the air bubbles during this process. Then, this creates a thin film with enclosed air that is trapped in between. This enclosed air is commonly called a soap bubble.
All Lathered Up
In conclusion, the reason that soap can do this whole process and create a lather is because soap contains surfactants (something that reduces the surface tension of a liquid that it is dissolved within). Soap must have some type of surfactant in it to perform properly. Surfactants can reduce the surface area of water while also being compatible with both water and oil due to its properties.
By reducing the surface area of water, this makes the water molecules more slippery, which in turn allows them to interact more with dirt and oil molecules. While it is not a simple process, it is not overly complicated, and you can remember this next time you go to wash your hands.
>>> Get the Inside Edge
Now that you know how to maximize the lather in your all-natural soap, consider offering it for sale. Real soap with high lather properties are in demand. Once you have a product that works, and people know about it, it can be hard to keep up with demand!
There is an article, on this site, that you can use to start selling your homemade soap right away. You can read How Do I sell My Handmade Soap, if you’d like, at your convenience.