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
{ 10 comments… read them below or add one }
Can I ask for the specific storage conditions in the accelerated stability testing and real-time stability testing of cosmetic products in ASEAN countries?
I would also like to ask for the specific procedures involved in it. Thanks!
Dear Perry,
In step 3: what should be the temperature of the freezer ?
I did the Freeze thaw cycles before and I have used different temperatures ex: 4C, -10C .
Thank you
Charbel – It doesn’t really matter that much. You just need it to be cold enough to freeze all the way through. 4C works for most products. -10C will work too but it’s not necessary how solid you freeze the sample. It just has to be frozen.
Interesting, is there an industry standard method you could point me at? I work with food but I assume this could be applied with anything that is like a cream. it would be an interesting comparison.
I have some doubts here:
How should we select the number of cycles and also the temperatures and what is the relation between these parameters and the field exposure?
I would like to validate our stability method in formulating cosmetic products. Generally, after product formulation, we put 50 g samples under accelerated temperature testing at 45 degrees and 60 degrees. We consider a formulation to be stable after 3 months at 45 C and 2 weeks at 60 C. Is our method correct?
A standard number of cycles for freeze/thaw tests is 3. I’m not sure I understand the second question.
Temperatures for a full stability should be near freezing, room temperature, and elevated temperatures. I’ve had success using the following temperatures. 4C, RT, 37C, 45C. But you might have different temperatures that are more convenient to use.
It really depends on the type of formula you are testing. 60C is probably too high a temperature to get any meaningful data for most products (esp. emulsions). The reason is that some of the raw materials will melt at that temperature and you get artificial negative stability results. If something is stable at 45C for 2 months, it is generally considered stable. Your 3 month standard is more extreme but if it’s stable there, then you’re in good shape.
Finally, 50g is probably not enough product to test. You should be using at least 100g. However, this depends on the formula too. If you are not testing viscosity then perhaps you can get away with a smaller amount.
Thanks Perry
This is a very usefull information.
Can u please explain Hlb Calculation For a w/o emulsion system.
Please see our article on HLB formulating. http://chemistscorner.com/hlb-the-easiest-way-to-create-an-emulsion/