knockout cosmetic experiment
Article by: Perry Romanowski

There are many different routes you can take to learn to become an expert formulation chemist but few are more powerful than conducting your own knock-out experiments. These type of experiments can help you learn a number of things such as,

  • 1. The function raw materials
  • 2. The performance effect of raw materials
  • 3. The formula effect of raw materials

It can also potentially lead to the discovery of a new formulation and cost savings ideas.

Formulation Chemist Knockout Experiment

The term knockout experiment was taken from the field of genetic engineering. In it, scientists create organisms in which they remove or “knock out” a specific gene. Then they see what effects the removal of a certain gene has on the organism.

In the cosmetic chemist’s version of a knockout experiment, you take a known formula and “knock out” a specific raw material. You then see what effect the absence of that raw material has on the final product. It’s a simple yet powerful study that can quickly get you familiar with any formula.

What will a cosmetic knockout experiment teach you?

When you first start your cosmetic formulating job, you will often start new projects with a formula that your company had previously developed. I remember the first formula I ever made (a shampoo) was originally developed by the guy whose notebook I inherited. My boss asked me to make samples to give to our Marketing group for evaluation. I had no clue about why any of the raw materials were used, what they did, or even how hard they were to work with.

You will undoubtedly be in the same position if you are just starting in this industry. Even if you’ve been around for a long time, it’s impossible to know the effect of raw materials in any formula you haven’t personally made (or observed being made).

Knockout experiments can rapidly tell you when making a batch exactly which ingredients have the most effect, which ones can be removed and which ones interact. When you’re done making the formulas, you can learn what raw materials have the most impact on the final specifications and the product performance.

The amount of information you can learn from a single knockout study makes it well worth doing on every new formula you are asked to work on.

How to conduct a cosmetic knockout experiment

Running a knockout experiment is fairly easy. All you have to do is take your initial formula and make a series of batches in which you remove one ingredient. If it’s a water-based formula, you simply add water to replace the missing mass.

Here is an example batch sheet for conducting a knockout experiment on a shampoo formula.  (Click to enlarge) As you can see, each subsequent formula has a line where the value of one ingredient is supposed to be.knockout cosmetic experiment

In this formula there are 8 unique ingredients which means you will need to make 8 different batches. The first batch is the control batch which should be made first. This ensures that you are able to successfully make the formula.

You should try to control as many variables as possible such as temperature, mixing speed, mixing time, etc.

Simplifying the knockout experiment

While it is best to make a new formula for each ingredient, this can become impractical and unproductive if there are dozens and dozens of different raw materials. In these cases you can minimize the number of batches to make by ignoring ingredients not expected to significantly impact the end performance such as

  • 1. fragrance
  • 2. dye
  • 3. extracts
  • 4. preservatives

If you don’t know which ingredients are superfluous, ask one of your more experienced peers. But be careful. It is wrong to make any assumptions about a formula. There could be ingredients you expect not to have any effect that do.

It’s worth noting that more complicated versions of this knockout experiment can be conducted using DOE (design of experiment) software. These experiments can give you much more information. Unfortunately, they also require many more batches to be made. In future articles we will discuss DOE further.

Evaluating your cosmetic knockout formulas

After you’ve made your batches you will end up with a series of formulas that need to be tested. At the very least you should take pH and viscosity measurements. You can then correlate the presence of any ingredient with an effect on those variables. This can be extremely useful if you need to help make adjustments on the production level in characteristics like pH, viscosity, texture, odor and appearance.

You should also conduct appropriate lab tests to see how the removal of a certain ingredient affects performance. For foaming products, conduct foam tests. For skin lotions, do a moisturizing test. Perhaps most important is to try the product out on yourself. Try to experience the product like a consumer. This will give you excellent clues about how important any raw material is to the overall effect of the formula.

Knockout your cosmetics

The knockout experiment is not a perfect way to learn all you can about a formula. There are important synergistic effects it will miss. That’s why DOE is often superior. However, you can’t beat knockout experiments for speed and ease. And you’ll definitely learn a lot about raw materials quickly. To become a great formulation chemist you have to make a lot of batches and try many different ingredients. The knockout experiment helps get you there faster.


About the Author

Perry Romanowski

Perry has been formulating cosmetic products and inventing solutions to solve consumer problems since the early 1990’s. Additionally, he has written and edited numerous articles and books, taught continuing education classes for industry scientists, and developed successful websites. His latest book is Beginning Cosmetic Chemistry 3rd Edition published by Allured.


  1. Avatar
    Jeffrey Ehlinger

    I read this article in the Ontario SCC Newsletter and would like to add a comment:
    If a formulator is doing cosmetic knockout experiment it can also be useful for them to look in the INCI Dictionary (PCPC) for the particular cosmetic ingredient and what’s listed under the “ingredient function” section as you mention in your previous article:

  2. Avatar

    hello Perry

    I am a chemist (MSc) that would like to get in to cosmetics and odor formulation.

    Do you know which university in Europe or America has strong focus on those topics?
    I would like to take some courses

      1. Avatar

        I want to make body butters, do i need any testing such as stability and challenge testing ? Also, what other testing do i need.

        1. Avatar
          Perry Romanowski

          If you want to sell the product, Yes. And you need testing for any type of claims you will make.

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  4. Avatar

    Hey! I’m 18, and I know I want to go into science when I get older– problem is, I’m kind of torn between trying to be a neurological researcher and trying to be a cosmetic formulator. What sort of degree would you recommend pursuing in order to leave both open as options? Thank you so much!

    1. Avatar
      Perry Romanowski

      You can study both Chemistry and Biology to leave both options open.

  5. Avatar

    Hey, I’m 13 and I would like to become a cosmetic formulator. I have been doing extensive research on how to become one, and what classes I should take, and so on so forth. Basically, I was wondering if you had any “advice” I suppose you could say on what to do. I’ve read the post on cosmetic chemist, but I was wondering if there were any other things I needed to do, or any easy experiments, classes, or extracurricular activities or such that I could do to elevate my chance of one day becoming a cosmetic formulator. Thank you!

    1. Avatar
      Perry Romanowski

      Mostly, you should focus on getting a college degree in chemistry. That will be the best thing you can do. And continue to read up on the subject. Following this website is a great idea.

      1. Avatar

        Hi Perry
        Why do I need a college degree to formulate cosmetics?
        You can play with the raw ingredients until you get a great product.

        1. Avatar
          Perry Romanowski

          Hello – You don’t need a college degree to formulate cosmetics. You do need a college degree if you want to get a job as a cosmetic chemist in the industry.

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  12. Avatar
    Peter Taylor

    Hi Perry,

    I was interested in your comment on the use of DoE software. I know this is now being widely used in pharmaceutical development, but how extensive is its use in the cosmetic industry?



    1. Avatar

      It’s not being used extensively but some companies are definitely trying to implement it. The primary hurdle with using DoE software for formulation is that there are no easy tests to determine whether something is better than something else. It is easy in pharmaceutical research to put a protein marker in solution and see if your new molecule or blend has a better reaction. In cosmetics you have to make a complicated formula and then do a performance test that takes nearly as long to conduct as it does to make a single prototype. DoE just doesn’t save much time.

  13. Avatar

    Hi Perry,

    These knock-out experiments help a lot to figure out a problem in the formula too.
    I performed this experiment on a formula with mal-odor. It really worked for me to figure out the ingredient causing the bad odor.

  14. Avatar
    Peter Roberts

    Hello Kuljeet
    Try doing the distance learning course from the Society of Cosmetic Scientists in the UK. Contact them via

  15. Avatar

    hey m pursuing chemistry honour from delhi university(graduation)
    i want to become a cosmetic formulator.
    Cn u plz help me n tell me which course should i do and from where? Plz

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  17. Avatar

    I stumbled across this site today while researching stability testing. I have been working as a formulation chemist in the paint industry for over 6 years now and had never heard of a knockout experiment, this makes perfect sense, I only wish I had read this 6 years ago. Thanks!

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  24. Avatar
    Roocha Khedkar

    Dear Perry,
    I want to know if we can do the knock our experiments to determine emulsions stability.

    Also, do we have a standard to finalize the emulsifier levels in the new formula with higher phase volume of emulsifiers should increase if the phase volume for say, W/O is 60/40?


    1. Avatar

      @Roocha – A knockout experiment is not the best one to do if you are looking to figure out formula stability. Knock-outs are best used when you have an existing formula and want to figure out the effects of the raw materials.

      For emulsion stability, you’ll want to do an optimization experiment in which you adjust the levels and ratios of emulsifiers, water, and oil phases. There is no real standard although you can use the HLB method to figure out the levels needed.

  25. Avatar

    Hey Peter,
    You are correct, the sample labeled ‘Control’ should contain 200 g of SLS
    Thanks. I’ll have to fix that.

  26. Avatar
    Peter Roberts

    Hello Perry
    I thought the control shampoo should contain the SLES?

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