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
{ 25 comments… read them below or add one }
could you please tell me the exact significance of specific gravity of cosmetic product?
I gone through many sites but couldn’t get the actual significance……..
I am a student of cosmetic technology.
Specific gravity is usually used in cosmetics as a determination of the amount of air that is in a formula. The more air, the lower the specific gravity. Ideally, your cosmetic product will have a specific gravity close to 1.0 If there is too much air in the formula, it gets lower. Of course, this really depends on the product you are making.
hi all,
I’m trying to study the freeze/thaw stability of my diaper rash water in oil cream !!
I’m cooling to -10 degrees and then to room temperature. ..
everything is ok.. but i have observed that once i try to stir the cream once he is cold i feel that i’m breaking him .. and water begin to sweat !!!
is it not allowed to do any stirring while the cream is very cold (at -10) .. !!
please would any one answer me !! ASAP
We are formulating creams having 10-20% sesame oil in cetostearyl-cetomacrogol1000 creams. but the formulations cannot tolerate the high temperature-freeze cycles (24hr-24hr) and separation occures. can anybody help us? creams have 20% sesame oil, 0-10% vaseline, 5-15% CEA-CMG1000 and 60-70% water.
Sir, I am doing my thesis work on anticellulite cream for my master degree course in cosmetic technology.I want to know abt stability of my o/w creame.the base formula should be stable but when I added my active drug ingredient in it the formulation shows seperation after 3-4 days.plz can you help me?what can i do to avoid this problem?Plz
Hi,
I am not a cosmetic chemist but household cleaners chemist, hope you would still reply me.
Most of our products are liquid (water thin).
Issues I am facing:
1) After a F/T cycle, darker color on the bottom and light to clear color on the top. Initially, I though it my surfactants are falling out – so added some hydrotop (SXS) but didn’t help. Any feed back would be helpful. Just an FYI: Particular product is All Purpose Cleaner. I am using 2 surfactants. 1 Anionic and 1 Non-ionic surfactants.
Not sure if that will help you, but both phrases have different specific gravity.
Any help would be greatly appreciated.
Thanks,
Mit
It’s difficult to guess without knowing the specific surfactants you’re talking about or what other ingredients are in there. But a separation like that sounds like a solubility issue. It could be related to the fragrance you are using, some cationic species in the formula or the concentrations of the surfactants. You could probably solve it by changing some of those factors.
hi, i have started a freeze thaw test cycles on a body spray product and in the first cycle i obtained precipitation in the sample, a darkened colour and a slight increase in the pH.
so, our first thoughts were that it is a solubility issue of a phase into another which had affected the pH thus the colour..
i am continuing the test cycles to see if there will be any more changes.
do uou have any suggestions for me?
Thans
It sounds like you have identified a stability problem. Without seeing the formula it is difficult for us to give any specific answers. Slight pH changes are not unexpected and do not necessarily mean there is a problem with stability.
How about water-in-oil emulsions sir, is there another way to measure pH?
While it doesn’t give completely accurate results, we just used a standard pH meter to measure pH of water-in-oil emulsions. This would only help identify gross changes however and wasn’t particularly useful. Why do you want to measure the pH of a system like this?
this corner really rocks! a lot of infos are in here…congratulations!
The was really served my purpose, thank you..
sir can you please give the references for this information.
thanks in advance..:
How do you measure the pH of an emulsion cream?
As long as it is a oil in water emulsion, you can use a pH meter.
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/
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?
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.
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?
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.
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.
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.
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!