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?
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.
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.
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 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.