Tag Archives: Cosmetic Stability Testing

cosmetic formulation testing

Cosmetic Formulating Blog Series | Testing the Formula

Cosmetic Formulating Blog Series | Testing the Formula

Now that we went over some of the basics of cosmetic formulating and how to build the formula, let’s go over testing the formula. Cosmetic formulation testing is an important step before going to market with your final product.

Adjusting the Formula

It is rare that you will have the exact product you want on your first try. Formulating is all about tweaking your formula till you get it exactly how you want it. It takes a lot of patience. Don’t get discouraged if it is not turning out how you want, as it may just take a little tweak to get it exactly where you want it!

When making changes to the formula, it is important you only make one adjustment at a time. It can be tempting to make several changes at once, but then you will not know which adjustment produced what kind of change. It is also important to allow time for the formulation to settle. Sometimes scents can take time to evolve and waxes to firm up.

pH Testing

pH stands for “potential for hydrogen” and is the system to measure acid and alkaline. Neutral pH is 7, anything below 7 is acidic and anything above 7 is alkaline. Water has a neutral pH. The more acidic or alkaline a product is, the more it will cause irritation to the skin. Generally the pH level for body and skin care products should be between 4.5- 6.0 and for hair care products between 4.0- 6.0.

There are a couple different ways one can test for pH. There are pH strips that are easy to use. The strips will give a range instead of the exact pH. A pH meter on the other hand will give you the exact pH and is more accurate. You will likely need to adjust the pH of your product and you can do this with natural ingredients.

Sample Labeling

It is important for you to keep excellent records and label your sample with several key information. This includes the date it was made, type of product, pH, and a reference number that links to the formulation in your lab notebook to refer to for more detailed information. That way you can return to your sample over the next several months to test its stability. You should test the pH, notice the scent and how it has evolved, and if there has been any separation or discoloration.

Testing for Bacteria, Yeast and Mold

Any product that contains water will need to be tested for bacteria, yeast and mold. There are different ways  to test your product.

Plate counts test if there is bacteria, yeast and mold in your sample. It will not tell you how long your preservation system will be effective.

Challenge testing is performed at at one month or two months. Millions of bacteria, yeast and mold will be injected into the product and it will determine if your preservation system is effective.

Stability Testing will test how your product reacts to very hot and cold temperatures.

Testing and Preservation Resources

It is very important to test your product and not only for the stability of the skin or hair care product, but also for bacteria, yeast and mold, and if the preservation system is effective. At Joan Morais Naturals we provide extensive information on testing and preserving your body and hair care products naturally and effectively in our professional product making courses. For information on these courses check out the following:

Professional Natural Skin Care Product Making Course

Professional Natural Hair Care Product Making Course

cosmetic formulation testing

Cosmetic Stability Testing – Pre Market Testing

Cosmetic Stability Testing

This is a series on pre-market testing. In a previous post I wrote about cosmetic challenge testing here. This post will address cosmetic stability testing.

Cosmetic Stability Testing

One of the common tests performed when developing a cosmetic is stability testing. Stability testing can be outsourced and performed in a cosmetic laboratory or the cosmetic formulator or manufacturer can perform his or her own do-it-yourself test.

Do-It-Yourself Stability Test

1. Make a large batch enough to fill a 2 ounce glass container and the final packaging (the containers the formulation will be in). These will be the samples for testing.

2. Label the sample containers with the testing date, identify the type of testing (stability testing) and the batch number.

3. Perform the tests below on the samples.

4. Examine the stability of the formulation. Record and log the results of the testing. Questions to put on the log:

Did the emulsification system keep intact?

Is the consistency (viscosity)  the same?

Did the color remain the same?

Did the scent stay the same?

Did the pH stay the same?

Heat Test
Place sample in a 122°F/50C degree oven or incubator for 2 – 8 weeks. This is a high temperature and maybe too high for some formulations that may melt. For those formulations and most formulations 113F/45C is sufficient. The formulation is very stable if it passes to 8 weeks at 113F/45C.

Freeze/Thaw Test
Place sample in the freezer and freeze overnight. Take the container out of the freezer and bring the formulation to room temperature. Repeat two more times.

Room Temperature Test
Store sample at room temperature 77F/25C. Check sample at 2 weeks, 4 weeks and 8 weeks. Retain sample and keep testing over 52 weeks.

Sunlight Test
Place the sample with sunlight exposure (near a window). Check sample at 2 weeks, 4 weeks and 8 weeks. Retain sample and keep testing over 52 weeks.

joan morais Joan Morais is a natural cosmetic formulator, instructor, author and the owner of Joan Morais Naturals. Joan assists product makers on how to make high quality, stable and effective natural body, hair and skin care products for personal use and a product making business.