Home Cosmetic Science Talk Formulating Seeking critique of my formula and methods

  • Seeking critique of my formula and methods

    Posted by kartz on June 25, 2024 at 2:40 am

    Hi everyone,

    I’m a beginner formulator who has spent a few months developing and testing this liquid shower gel formula. While I’m not a professional, I’ve done my best to conduct stability tests at home. I’m eager to improve and eventually sell my product, so I would greatly appreciate any input from professionals on this site. Thank you for taking the time to help!

    Liquid Shower Gel Formula

    • 8% Sodium Coco Sulfate
    • 8% Cocomidopropyl Betaine
    • 4% Coco-glucoside
    • 2% Glycol Stearate
    • 1% Essential Oil
    • 0.8% Fragrance
    • 14% Polysorbate 20
    • 1.5% Niacinamide
    • 53.5% Water
    • 1.5% Optiphen Plus
    • 5% Glycerin
    • 0.7% Xanthan Gum

    Some Issues:

    1. Surfactant and Emulsifier Ratios: I’ve used a 1:10 ratio of Polysorbate 20 for essential oil and a 1:5 ratio for fragrance oil. Is this excessive? (My essential oil dissolved in water with 1:1 ratio, but I just wanted to be sure.)

    2. Preservative Usage: My supplier recommended 0.5 to 1.5% Optiphen Plus for preservation. I opted for 1.5% to ensure effectiveness, but how do I determine the correct amount for a 2-year shelf life?

    3. Stability Concerns: I conducted stability tests on my sample. While there was no separation at cold or room temperatures, heated conditions led to the appearance of white particles and a thin layer of translucent liquid at the bottom within one week. What might be causing this issue?

    4. Please feel free to leave your comments on anything I might be doing wrong as well.

    Perry44 replied 3 weeks, 1 day ago 2 Members · 1 Reply
  • 1 Reply
  • Perry44

    June 25, 2024 at 7:38 am

    I see a few problems with your formula.

    1. You include too much essential oil. The whole purpose of a shower gel is to REMOVE oil. When you put oil in your formula you cause two problems. First, you reduce the amount of surfactant available to clean the surface. Second, the essential oil is already tied up in a micelle and will just rinse down the drain. It is a complete waste of resources to include an essential oil, especially since you already have a fragrance! There are only two reasons to include an essential oil in a cleansing product. You need it for the odor or you want to tell a marketing story. If it’s a marketing story, you only need to add like 0.1%.

    2. If your home stability test did not involve a Preservative Efficacy test then you haven’t really done a stability test.

    3. Determining the correct amount for a 2-year shelf life is done just how you’re doing it. Use the highest amount you can safely add. Then when you find that is effective you can try to optimize the formula by using less. Of course, for that preservative you also need to keep the pH near or below 5.0 since Sorbic acid is one of the ingredients.

    4. Niacinamide is water soluble. It is simply rinsing down the drain and doing nothing in your formula. Using it at 1.5% is just a waste of money. In a rinse-off cleanser, it is what is known as a “claims” ingredient. You put a tiny amount in there to get consumers to buy the product. It doesn’t have any effect on the skin.

    The separation is most likely caused by the essential oil separating. Reduce the level since it is a pointless ingredient anyway.

    Finally, if you are going to sell the product you need to have it stability tested by an independent lab. Home stability testing is just not appropriate for a commercial product.

    Hope that helps!

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