Knowing how to create a stable emulsion is crucial if you want to sell cosmetics. If you don’t know what an emulsion is, then you can read this blog here. Also, if you want tips on how to create a more stable emulsion, then read this blog here.
Before you start selling a product you must have it undergo testing to make sure it is stable enough;
Your product needs to have a good preservative system so it doesn’t grow yeast, mold, or bacteria. We will talk about how to test that in a future post.
The emulsion needs to be tested to make sure it is stable and doesn’t separate over time (talking about that in this post)
Your product and it’s packaging needs to be tested to make sure its not UV sensitive. Meaning, will light cause stability issues for your product? You can learn how to do that test HERE
Shipping test, will your product leak, break or become unstable during shipping? This will need to be tested.
You can also get your product lab tested to have a shelf life determined for your product HERE
Instead of testing your products preservative system at home, you can instead have your products preservative system tested by a lab HERE. They offer all kinds of product stability testing if you aren’t comfortable with doing your own.
Also, while doing any type of stability testing to your product you also want to look out for any color changes, changes to it’s scent, viscosity, pH, and, if possible you can even check the particle sizing under a microscope.
Now, with all that said, let’s talk about the two methods you can do at home to test the stability of your emulsions.
Cycle Testing
Place your lotion in whatever packaging you plan to sell it in. Put the product in your freezer (-10°C/14°F) for 24 hours. Take it out of the freezer and then keep it at room temperature (25°C/77°F) for 24 hours. Place it back in the freezer for 24 hours, back in room temperature for 24 hours. Place it back in the freezer for 24 hours & back in room temperature for 24 hours. So you are doing 3 cycles of placing in the freezer for 24 hours and keeping it at room temperature for 24 hours. If your lotion shows no signs of separation after doing this, then that is a great sign you have a stable emulsion.
A more rigorous version of this test is, placing your product in the freezer (-10°C/14°F) for 24 hours. Then placing in an Incubator at (45°C/113°F) for 24 hours. Place product back in the freezer for 24 hours and then back in the Incubator for 24 hours. You want to do this cycle 5 times. This is a more rigorous test and what I recommend doing if you have an Incubator.
Centrifuge Testing
Heat your emulsion to 50°C/122°F and pour into a Centrifuge Test Tube. Place the test tube in your Centrifuge and let spin for 30 minutes at 3000 RPM.
The dispersed phase of an emulsion tends to separate and rise to the top of emulsions. This is called “Creaming”. This centrifuge test is a great way to test for creaming to get pretty quick emulsion stability results. Centrifuge testing is a necessity for products that contains powders like liquid/cream makeup.
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