Article by: Perry Romanowski

I remember learning about surfactants in first year college chemistry. It covered one page of Zumdahl Chemistry, and we spent exactly 5 minutes covering it. It came up again briefly in Organic Chemistry and that was about it. Surfactants were just not important.

That’s why I found it strange to learn that in the cosmetic industry, surfactants are the cornerstone of nearly all formulation and cosmetic science in general. To be a great formulation chemist, you have to know the chemistry of surfactants.

Surfactants Reduce Surface Tension

There are various places you can find background information about surfactant chemistry such as here and here, but we’re going to focus on what is most important for cosmetic chemists to know.

The key thing to know about surfactants is that they are chemicals which have parts that are both hydrophilic (water loving) and lipophilic (oil loving). This molecular composition means they have the ability to reduce the surface tension when placed into solutions of oil and water. In fact, the word “surfactant” is a shortened form of the phrase “surface active ingredient.”

While it may make sense that surfactants reduce surface tension, you might be wondering what that means from a practical application standpoint. We’ll look at that next.

How do cosmetic surfactants work?

When surfactants are put into solutions, the molecules have a tendency to line up in a certain way depending on the solution composition, the concentration of the surfactant, and the temperature.

In a water solution with extremely low surfactant concentrations, the molecules tend to bounce around randomly without forming structures. But at the Critical Micelle Concentration (CMC) they arrange themselves in spherical structures called micelles. On the outer layer of the spheres are the hydrophilic parts of the surfactant molecule and on the inner layer are the lipophilic parts. It’s a bit like a cream filled donut.

Increase the surfactant concentration and more complicated structures result such as hexagonal cylinders, lamellar planes and liquid crystals. Since this is an introduction, we’ll stick with the micelle structures.

Surfactants uses cosmetics

Now that you know about micelles, you’re ready to learn practical applications of surfactants in cosmetics. Surfactants are useful for the following application.

1. Cleansing
2. Emulsification
3. Solubilization
4. Conditioning
5. Special effects

Cleansing Surfactants

The useful thing about micelles is that they can help suspend oil in water. When a small amount of oily materials is put into an aqueous solution of surfactants, it will migrate into the center portion of the micelle. So, when you put a surfactant solution on a surface like hair or skin, the oil that is there will be drawn away from the surface and into the micelles. When the surfactant solution is rinsed away, the surface is clean.

For a graphical explanation of this process, see this short instructive video about surfactants (requires a Flash player).

Foaming

Foam is another characteristic of surfactant solutions so you’ll need surfactants if you want your product to foam. Essentially, foam is the entrapment of air in liquids and the alignment of the surfactant molecules helps keep the foam stable. It should be noted that foam itself is not related to the ability of a product to clean. But consumers expect cleansing products to foam so as a cosmetic formulator, you’ll have to add foaming surfactants.

Emulsification

While cleansing cosmetics remove oils, many cosmetic products are design to add oily materials to the skin and hair. These ingredients usually can’t be applied directly because they have undesirable aesthetic characteristics in their concentrated form. For this reason, cosmetic chemists create emulsions using surfactants.

A full exploration of emulsion science is beyond the scope of this entry so suffice it to say, emulsions are semi-stable mixtures of oils and water. A surfactant, or emulsifier, is used to help blend and stabilize the mixtures.

In the simplest case, an emulsion formula is made by mixing an oil phase with a water phase and a surfactant. The micelles created by the surfactant entrap the oil in their centers and it remains suspended throughout the mixture. Products like creams and lotions are typically emulsions. When the product is applied to the skin or hair, the surfactant micelles break open and deliver the oily materials.

Solubilization

The problem with most emulsions is that they usually create opaque products. However, there are times when a cosmetic chemist wants a clear formula but still wants to blend an oil in a mostly water formula. Fortunately, there are surfactants that have the ability to create particles so small that light passes through them and the solutions remain clear. Molecules that do this are solubilizing surfactants. They are used to blend oily materials like fragrances or natural ingredients into clear solutions. An example would be a surfactant like Polysorbate 20.

Conditioning

Since surfactants often contain an “oily” part on their molecule, they have conditioning properties that can improve the feel and look of the surfaces of skin and hair. For them to work this way, the surfactants have to be left behind and also be non-irritating. This can be achieved through a leave-on cosmetic product or by using surfactants that can bond to surfaces through an electrostatic charge (more on this later).

Special effects

In addition to the four properties discussed, surfactants have a number of other special effects that are useful to formulators.

For example, some surfactants have anti-microbial effects so they can be used as a preservative. Certain surfactants can be used to create an elegant, pearly effect in cosmetics to increase their aesthetic appeal. They can be used for thickening systems, reducing irritation and improving formula stability.

In part 2 of this surfactant series,  we  examine the different types of surfactants and how they are applied to cosmetic formulations.

24

24 comments

  1. Pingback:Surfactants: They ain't just for washin' -

  2. Pingback:Surfactants: They ain’t just for washin’ – curlytea

  3. Ghaida

    I make oil-in-water lotion, the consistency is good but the pH is too high, it’s 11. And it should be around 7. Can you help me what is wrong with my formula? And give me suggestion what should I do to fix it? Thanks in advance.

    Water Distilled 70%
    Glycerin 12.63%
    Triethanolamine 3%
    Carrageenan 0.3%
    Cetyl Alcohol 3%
    Virgin Coconut Oil 3%
    Almond Oil 5%
    Sorbitan Trioleate 2.655%

    1. Perry Romanowski

      It looks like your Triethanolamine level is too high. Reduce the level and it will bring the pH down. Also consider running a knockout experiment.

  4. yahya

    i am formulating mosquito lotion with deet but it separated after a day .am using stearic acid .cetyl alxohol .paraffin emulsifying wax.and 70 per of water .plz guide me with percentage.
    thanks

  5. Pingback:PRODUCT SPOTLIGHT: MICELLAR WATER – PALE AS F*CK

  6. Chukwuleta

    Am working on a shampoo and am confused on the surfactant to use and in my locality,the commonest one is sulfonic acid( a dark brown thick solution that foams very in water).so,is it ideal for a shampoo production?

    1. Perry Romanowski

      No. Sulfonic acid is not a good choice for aesthetic reasons and because it is not a surfactant.

  7. Hannah

    Can you please create a part three listing all (or most) products with surfactants because I am testing home makeup removers and I want to know whether some products that people say will remove makeup ie lotion, conditioner, witch hazel, etc.

    1. Perry Romanowski

      Nearly all products contain surfactants. But if you are looking for cleansers then look for products that contain ‘lauryl sulfate’ or ‘laureth sulfate’

  8. Hilal

    Is there any product of pressed face powder including carboxymethyl cellulose CMC in its constitution? Any article refers to this subject?

  9. Brad

    I have a glycerine based moisturiser, is there a way to solubilise the fragrance oils to keep it clear?

    1. Perry Romanowski

      That’s not enough information to answer your question. You need to provide the whole formula & specifications. Usually, you can use a solubilizer like Polysorbate 20

  10. Pingback:Kozmetik Ürünlerinde Sürfaktanların Kullanımı | Kimyaca

  11. Prof. Man Singh

    The surface tension, interfacial tension, wetting , dewetting , viscosity , surface excess concentration of the surfactants are highly useful data. Borosil Mansingh survismeter measure them together.

  12. myra

    im really interested in becomming a cosmetic chemist but i keep running into brick walls every time i research i start college next semister studing chemistry an i need as much info on my interest as possible any info will be greatly appreciated

    1. Perry

      Feel free to go through the material on this website. It has everything you need to know to get started in a career in cosmetic chemistry. Start with the ‘Career’ category on the right side.

      1. myra

        thank you so much . do you think my career as a experienced hair stylist an instructor will be beneficial to my study in cosmetic chemistry

        1. Perry

          It will definitely help you since you will have a good knowledge of products that are used and what they do. Just be prepared to “unlearn” some things that you might have been told by marketers who were selling professional products to the salon.

  13. Nami styve

    it is very interesting all what have been said.i wish to specialise in chemistry of the surfactants an its applications,but i do not have informations of appropriate universities.i will be very happy for any vital information.especially universities in Germany,England and USA.i have a bachelor degree in chemistry.

    1. Perry

      Nami – Take a look at the ‘Career’ tab on the right side. There is a post about all the cosmetic science programs around the world.

  14. Pingback:Emulsions Made By Bouncing Oil and Water Droplets

Leave a Reply

Your email address will not be published. Required fields are marked *