What are surfactants, and how do they work? When you start out making your own homemade things, you’ll find that a lot of the different ingredients you use can be totally unknown to you. While you know what adding them is important, sometimes it’s difficult to quite understand why.
When I started out, surfactants were firmly in this category. I was adding them to different homemade skincare products, seeing great results, but never really understanding what was actually going on. All I knew is that they would help a product foam, maybe solubilize a bit of oil in water or perhaps add some conditioning power to say a conditioner.
After years of on and off research, I began to understand what these mysterious ingredients actually are. So I thought that maybe it would be helpful if I aided others in their journey to becoming more informed skincare formulators. Today, I’m pulling back the curtain on surfactants, in a way that I hope is easy to understand.
What Is A Surfactant?
So, what is a surfactant? A surfactant is a compound that decreases the surface tension of water molecules. If you allow few drops of water to land upon a flat surface, you’ll notice that these water droplets tend to form little domes, instead of spreading out.
This is because water molecules are hydrophilic, which means they love over water molecules and will stick to them when possible. So instead of the droplet of water spreading out so all the molecules lay flat, they stick together.
When you are attempting to clean something, water clumping together like it normally does can be problematic. By adding a surfactant, it is possible to get a surface wetter, and in turn, you are able to clean it more easily. But how is this relevant to skincare? Let’s take a look.
Why Are Surfactants Important In Skincare?
Surfactants have many uses in skincare, but the most important is this amazing ability to clean. If we take a look at a surfactant under a microscope, you will notice it is comprised of molecules that are known as ‘micelles’. These micelles are the little structures that are responsible for the cleaning power of various soaps.
When you wash your hands with a liquid soap that contains a natural surfactant, these micelles help to break down and remove the dirt and grease that can get onto our skin. I have explained how this process works in my saponification post and my all about lye post, but I will explain again here.
These micelles have a water-loving end and an oil-loving end. When they come into contact with dirt or grease, the oil-loving end of these micelles attaches to the oily molecules within the dirt or grease. As you follow the motions of handwashing, these micelles will pull the oil molecules away from their friends, and eventually encapsulated them in micelles so they cannot stick back together.
This is why soap is so good at cutting through grease. It essentially tears the molecular structure of the grease apart, isolates each of its molecules so this structure cannot reform and then allow them to slip from your skin and down the plughole.
What Are The Different Types Of Surfactants?
There are many, many different surfactants on the market, but usually, they fall into 4 different categories. While all of them will reduce the surface tension of water, some will add other qualities to a product that may be beneficial.
Some add foaming capabilities, others don’t. Some will help solubilize small amounts of oil into water, so your products do not separate as easily. Others are super compatible with other surfactants, while others you may have to use them on their own.
Ultimately, these categories are defined by the charge that is associated with surfactant molecules. Some surfactants have a positive charge, others have a negative charge. Some even have both, and others have no charge at all. So let’s break down these categories in a little more depth.
Anionic surfactants have a negative charge and are favored for this powerful cleaning and foaming properties. SLSA is a good example of an anionic surfactant. Another anionic surfactant you are probably familiar with is regular soap. Yup, good old bars of soap! Anionic surfactants are often combined with others to produce a product that is both powerful and gentle on the skin.
Nonionic surfactants have no charge at all. It is perhaps the second most common surfactant found in skincare products, after anionic. They provide good cleansing, however, tend to be much more gentle on this skin than anionic. Anionic and nonionic surfactants are often combined together to produce a good quality product that is also suitable for those with sensitive skin.
Cationic surfactants carry a positive charge. They provide almost zero foaming ability to any product, and so for that reason are favored in recipes that do not call for foam. The most common of these are conditioners.
Human hair generally carries a negative charge, and so the positive charge in cationic surfactants are attracted to them. This makes a product that contains a cationic surfactant much more difficult to properly wash out of your hair, meaning some of the ingredients in your lovely conditioner will stay in your hair, keeping it softer or shinier for longer.
Cationic surfactants will also reduce the amount of friction that naturally takes place when your hair rubs together. This reduces electrostatic charge, and in turn, makes your hair much less frizzy.
Amphoteric surfactants are a strange one, as their charge can be either positive or negative. The shift in charge of this surfactant is generally caused by the PH of your product. On their own, they tend to be quite gentle and do not add a significant amount of foam or cleansing power. However, they are compatible with nearly all other surfactants, so they are great for combining with anionic surfactants to reduce harshness but still provide a solid, stable foam.
Are Surfactants Natural?
But are surfactants natural? Well, not all of them. However, there are plenty of natural surfactants on the market that are widely accepted in natural skincare. Let’s take a look at some of them.
Coco glucoside is a natural, nonionic surfactant that is derived from coconuts and sugar. It provides a good foam, and because it is nonionic is a great co-surfactant. I like to use it in combination with other natural surfactants in my liquid soap recipes.
This surfactant produces a lovely foam, making it perfect for various bath products, shower gels, body washes, and foaming cleansers. While it provides no real skin benefits besides foaming and cleansing, it will not dry out your skin like many other surfactants, and it’s perfect for baby products.
When using this ingredient, try to stir it in slowly and gently. As with all surfactants, they have a tendency to foam when you work with it, rendering the product useless. As long as you’re careful, you should have no problems.
Decyl glucoside is similar to coco glucoside, as it is a natural, nonionic surfactant. It is quite gentle on the skin, and provides some good foaming. However, I would use it as a co-surfactant for a better foam.
Another of the glucoside surfactants, and again is very similar to the two we just discussed. It is natural, nonionic and gentle on the skin. I would use it as a co-surfactant.
Coco betaine is a natural, amphoteric surfactant that provides a decent foam. This surfactant should not be confused with Cocamidopropyl betaine, which is very similar and has many of the same characteristics as Coco betaine, except it is not natural and not accepted in natural skincare.
It is also worth mentioning that Coco betaine has larger molecules than Cocamidopropyl betaine and so can be a little harsh on the skin. It is a great co-surfactant for a nonionic surfactant, such as one or more of the glucosides mentioned above.
Sodium Coco Sulfate
Sodium Coco Sulfate is an anionic surfactant that is a good alternative to SLSA, but will not perform as well. It does still produce a decent foam, however. It is water-soluble and widely accepted in natural skincare.
Plantapon® SF is the trade name of a non-ionic surfactant that is accepted in natural skincare. It produces a rich, dense foam that is very desirable whilst also being quite gentle on the skin. However, as it is a surfactant that has been designed by a particular company and is not a generic compound, it is sometimes more difficult to come across depending on where you live.
However, if you can get your hands on it, it is a good surfactant to work with, specifically if you have not worked with surfactants before. It works very well on its own and doesn’t need to be combined with anything else.
Liquid Yucca Extract
Okay, so this one is a bit of a strange one but is worth mentioning because it is the only surfactant on this list that is 100% natural. While others are considered natural, it is important to keep in mind that they are not the pure extract of a plant. However, liquid yucca extract is, and you should totally check it out.
While it is purely natural, nonionic surfactant that is very mild and gentle, it is important to keep in mind that it isn’t really very good on its own. If all you had was yucca, that would be okay, I would strongly recommend combining it with another nonionic surfactant, or perhaps an anionic or amphoteric surfactant.
I hope this post has been informative, and that the information has been relatively easy to digest. While all the information on this page may not necessarily be important to understand, I feel like getting to know the different ingredients we use is a big step for any new formulator.
If anything is unclear, just drop a comment below and I’ll do my best to answer you. You can also drop me an email!