Article by: Perry Romanowski

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 freeze thaw scientistformula, 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

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56 comments

  1. ramana

    Why 24hrs?

    1. Perry Romanowski

      It takes that long to ensure it freezes all the way through

  2. Kasun

    I read the article on Freeze Thaw Cycles. It has mentioned that for 3 cycles it takes 3 weeks (21). But in one cycle, 24 hours in freezer, 24 hours in room temperature and again 24 hours at 50 C, 24 hours in room temperature. Therefore, for one cycle it takes 4 days and for 3 cycles 12 days. Pleas clarify this…..
    Thanks

    1. Perry Romanowski

      Yes, you can do it faster. When you work at a company it takes 3 weeks because you work Monday – Friday

  3. Karthi.R

    Thanks for your wonderful guidance! I am formulating silicone emulsion(O/W) for textile applications. Could you please explain about(1)Importance of emulsifier concentration for freeze-thaw stable silicone emulsions(2)Factors affecting the freeze-thaw stability of silicone emulsions.

  4. Mona

    Hi Perry:
    I am working on formulating a lip liner, I just performed first freeze/thaw stability test on the samples. Freeze thaw samples show a slight change in texture, they are softer and creamier that room temperature and 45 degree samples. Since the formula has high content of wax do you think the problem is due to improper wax/emulsifier ratio?

    BTW Thanks you for your very informative and helpful website and webinars.

    1. Perry Romanowski

      Hello Mona,

      It’s difficult to answer without seeing the formula but you probably have the ratio of wax and emulsifiers and oils off. I’d suggest you post the question in our cosmetic forum to get the input of more chemists.

  5. Pingback:Cosmetic Test | Cosmetics

  6. Paola

    Hi

    I`m developing a o/w cream. When i do the freeze/thaw cycles the emulsion is ok (it`s not separated, not visible liquid in the surface or in the bottom) but the appearance in the spatula is like it has little aggregates, but when i try it the aggregates dissapear. Is it a normal result?

    I`m doing only freeze, thaw an try it, it means I put the samples in the freezer (24h)and after room temperature (24h) and try it (i`m not putting the samples at 50C), is it ok?

    Thanks!

    1. Perry Romanowski

      No that’s not normal. It’s indicative of product instability.

  7. Leanne

    Hi Perry,
    I very much enjoy your website and find it very helpful and practical to our field. I also heard you speak at the conference in Kiawah last year and found it informative. I have a question about Freeze Thaw testing. After a couple of cycles of freeze thaw conditions, our sample went from smooth a creamy to a rougher, more airy texture. The sample was homogenized during manufacturing. How would you recommend proceeding from here?

    1. Perry Romanowski

      Hello Leanne – it sounds like your formula has some stability issues. How is the rest of the stability test going? Without knowing the formula it is hard for me to give you any suggestions. You probably need to adjust your combination of emulsifier and oil level.

  8. dale

    I am working on a value line of shampoos that I just took through freeze/thaw stability. The total solids level are pretty low (6%) and I need to add something that will increase the tolerance to low temperatures. Cost is an issue since this is for a value line of products.

    I have been looking at other comparable products (ex. Suave) and it looks as if there that maybe a Carbopol or Xantham gum could help.

    Any input?

    Thanks

    1. Perry Romanowski

      What do you mean by “increase the tolerance to low temperatures”? Is the product separating? When I worked on a value shampoo line the product would freeze at low temperatures but then it would thaw and be perfectly fine at room temperature.

  9. Abdullah Ali

    Hi Perry,

    I attended your webinar in stability studies with UL Prospector 2 weeks ago. First, I would like to thank you for a very useful and instructive webinar.
    I have a question regarding freeze thaw studies when performed in stability testing. You showed a scheme for an example stability test in your power point with freeze/thaw in 2 weeks, 4 weeks, 8 weeks.

    I wonder if this means that freeze thaw studies are done on the samples that has been going for 2 weeks , 4 weeks and 8 weeks and then tested for freeze thaw stability? Or do you start freeze thaw study from initial samples and run a number of cycles?

    Kind regards,
    Abdullah

    1. Perry Romanowski

      Hello – thanks for the kind words. No, freeze thaw are done on fresh samples and usually in the first 2 weeks after you make the batch. The chart is a little unclear but that’s how we do it.

  10. Rachel

    Hi Perry,

    Can I use this Freeze / Thaw test to predict my product shelf-life?

    1. Perry Romanowski

      Yes, that is one tool to use. It’s not a replacement for a full stability test however.

  11. flora

    tanks for your good information.
    how we can doing freeze thawing method in agar extraction from algae?
    if it possible write a process sequence.

    1. Perry Romanowski

      Sorry, I’ve never done that before.

  12. Atchara

    Dear Perry,
    Can I apply this method (freeze-thaw cycle) in household application?
    Thank you for useful information.

    1. Perry

      Yes, this testing would work with household formulations.

      1. Atchara

        Thank you very much for your reply. Could you please share me related link or books about freeze-thaw cycle?

        1. Perry

          I only know of the freeze-thaw cycle because of my formulating job. It was a standard method we used. It’s also used around the industry but I don’t know of any books that will have a description of it.

          1. Atchara

            Ok, Thank you very much for your kind

  13. Gian

    Hi Perry

    Do you do freeze-thaw in glass packaging or in the actual packaging?

    Thanks
    Gian

    1. Perry

      Ideally, you do it in both. Glass is good because you are better able to see stability problems. However, packaging is more reflective of what your product will experience in the real world.

      1. Gian

        Thank you a lot Perry! Didn’t expect you would reply at this point in time. Have a happy and festive Christmas! 🙂

  14. shikkha

    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.

    1. Perry

      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.

  15. Geo

    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

  16. Hossein Yousefi

    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.

  17. karuna ghodkir

    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

  18. Mit Bhandari

    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

    1. Perry

      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.

  19. pia

    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

    1. Perry

      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.

  20. cris baysauli

    How about water-in-oil emulsions sir, is there another way to measure pH?

    1. Perry

      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?

      1. Deja

        Perry,
        I know that this is an older post but any insight would be greatly appreciated! I am curious of why you are questioning measuring the pH of water-in-oil emulsions, is this test not needed? My reasoning for testing the pH would be mainly for preservative effectiveness.

        1. Perry Romanowski

          When you have a water-in-oil emulsion there is no continuous water phase. The water is tied up on the inside of the micelle particles. So, your pH probe does not measure the pH of water because it doesn’t come into much contact with it.

  21. Shalini

    this corner really rocks! a lot of infos are in here…congratulations!

  22. chaitanya

    The was really served my purpose, thank you..

    sir can you please give the references for this information.
    thanks in advance..:

  23. Scott Fraser

    How do you measure the pH of an emulsion cream?

    1. Perry

      As long as it is a oil in water emulsion, you can use a pH meter.

  24. Prajakta Bhuskute

    Thanks Perry
    This is a very usefull information.
    Can u please explain Hlb Calculation For a w/o emulsion system.

  25. cris baysauli

    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?

    1. Perry

      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.

  26. Bahman

    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?

    1. Perry

      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.

  27. Lisa

    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.

  28. charbel Haddad

    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

    1. Perry

      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.

  29. Joana Lou

    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!

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