Previously, we covered the basics of cosmetic stability testing. But one member of the Chemists Corner community wanted some more details on Freeze Thaw testing. We’ll look at that aspect of stability testing in a little more detail.
What is Freeze Thaw testing
Freeze thaw testing is a type of stability test in which you freeze your formula, then thaw it out, and test to see what effect the process has on your product. To do a thorough freeze-thaw test you will repeat the cycle a few times.
Why do Freeze thaw testing?
Freeze thaw testing gives you information that regular stability testing can’t. Namely, it will show you whether your formula will remain stable under varied conditions that it might experience during the shipping and storage phases of the product life cycle.
It’s likely that your product will be shipped via trucks or rail cars. These vehicles are rarely equipped with temperature controls so it is likely that your product may freeze one day and be in hot temperatures another. It is crucial that your formula is able to withstand extreme, rapid temperature changes.
How to conduct a freeze-thaw test
While there is no “right” way to do a freeze-thaw test, the following method is standard in the industry and will give you the information you need if you follow it.
Step 1 - Prepare samples. (3 test, 1 control)
Step 2 - Take initial readings.
Step 3 - Put test samples in the freezer for 24 hours
Step 4 - Remove samples and allow to thaw at room temperature
Step 5 - Put samples in 50C oven for 24 hours
Step 6 - Remove samples & allow to equilibrate at room temperature.
Step 7 - Take end of the cycle readings
You should repeat this test through 3 cycles. If done correctly it can be completed in 3 weeks.
What to look for
While the specific tests will depend on the type of formula you are testing, generally you’ll want to take readings for Appearance, Odor, Viscosity and pH. Make particular note of whether there is any separating at the top or the bottom of samples. This is the most common form of instability.
You may also test the products for performance characteristics just to ensure that the formulas still work as expected.
Do you have any questions about stability testing or other cosmetic science topics? Send us an email or leave a comment below