Home Cosmetic Science Talk Formulating Stability Thoughts

  • Stability Thoughts

    Posted by Iwana on December 3, 2021 at 9:44 pm

    Hi Guys,
    I would like to have your thoughts on something.

    When you put on cosmetic products on Accelerated Stability, how do you put it ?
    So what I do normally is I put the cosmetic product in the container that it is going into the market in and then place it in the oven.

    But one or my co workers today was wondering when someone uses the lotion or cream they will pump the bottle or open the jar and use. But when we do stability we just put the bottle inside and check up on it every week and there is no much air going inside. This will not tell us the right stability of the product.

    According to me the only thing is when a person opens and closes the product or pumps the product out and air goes in is that the microorganisms enter, the stability is not changed. We add the preservative and anti oxidant to do their jobs here, for this case. 

    My thinking maybe wrong. So I would like to know what you’ll think!

    If anyone has any links to tell me more too will do. 

    oldperry replied 2 years, 2 months ago 4 Members · 7 Replies
  • 7 Replies
  • PhilGeis

    Member
    December 3, 2021 at 10:44 pm

    You’re correct. Stability (PET) indirectly addresses the chemical stability of the preservative system.  Opening/closing/pumping is largely irrelevant to chemical stability - I’m familair with only one preservative that might be sensitive.
    The stupidity of PAO takes this to the extreme.  - stability doesn’t start until the package is opened.

  • oldperry

    Member
    December 4, 2021 at 2:17 pm

    Stability testing is supposed to represent a model of what happens under real world conditions. It is not a perfect model and the results can only give you a prediction of what will happen in the future. But it’s quite possible something passes stability testing then on the market it isn’t stable. 

  • gordof

    Member
    December 6, 2021 at 7:21 am

    What your co Worker is telling you is in my perspective one possibility.

    We normally do an “In use Stability” next to the “nonuse stability” to clarify if there are any problems. Especially for Pumps and Sprays, it would be Recomadabel to do it.

    They can have problems with blockage, thickening over time and I even had the problem that the pump did not work anymore if the Product was in the wrong position (upside down) for more than 10 days because the Product did interact with the mechanism. 

    it is an additional test that can give you further intel. not so much about product stability itself but for interactions and usability of the Product and the Packaging over time and use live cycle so to say. 
  • PhilGeis

    Member
    December 6, 2021 at 11:36 am

    Gordof makes an excellent point reagrding functionality.  In-use testing is also important to understanding if your preservative system as qualified actually works for consumers.    Woukd be a good idea esp. for those using USP 51, a [pretty [oor asseassment device for cosmetcs.

  • Iwana

    Member
    December 6, 2021 at 3:12 pm

    Yes I agree with you. In use test is important factor. But does that effect the stability or only the PET or microbial ?

    My co worker today said that the Accelerated Stability test is not good enough. As only when air enters into the product do we actually know if the product is stable.
    He said that when the product is kept open then only does oxidation take place and that when placing it in the oven Oxidation does not take place. 
    And when we put the product in the original packaging and then place it in the oven the air does not enter and it does not even undergo oxidation.

    I feel the oven give us the chemical stability. Even if the product is in the pump bottle or not it can still undergo oxidation.

    Also do you think when the product is new formulation does it have to be put on 45℃ at 60%RH for 3 months a must Right ?
    I was used to working for pharmaceutical before for us it was a must for FDA approval. But here cosmetics I am not too sure.

    Because again my co worker said that it is not a must to do that. He feels that only way to know product is stabile is to again check how the product will act when pumping it out over a period of time in exposer to air.

  • PhilGeis

    Member
    December 6, 2021 at 3:40 pm

    Iwana said:

    Yes I agree with you. In use test is important factor. But does that effect the stability or only the PET or microbial ?

    My co worker today said that the Accelerated Stability test is not good enough. As only when air enters into the product do we actually know if the product is stable.
    Because again my co worker said that it is not a must to do that. He feels that only way to know product is stabile is to again check how the product will act when pumping it out over a period of time in exposer to air.

    Think your coworker is mislead by the PAO BS.  Air is already present in the package.   

  • oldperry

    Member
    December 6, 2021 at 4:09 pm

    You have to begin with the question of why stability test is done in the first place. Stability testing is supposed to help you predict what will happen to the product during shipping, storage, on store shelves and when used in a reasonable manner by a consumer.

    Stability testing is not done to see if you can make the formula oxidize or otherwise break down.

    We put the product in final packaging because that is how the product will exist out on the market. 

    We test heated up versions of the unopened product because that is what the bottles will experience when put into vehicles, shipped across countries, and stored in manufacturing facilities. It’s also why we test freeze thaw samples.

    There is also the notion that the speed of chemical reaction will occur twice as fast with every 10C increase in temperature.  The Arrhenius equation I believe. So, if you want to know what might the formula look like in 1 year at RT, you can increase the temp to 35C for 6 months, or 45C for 3 months.  It’s not an exact science but that’s the idea.

    To me, RH does not really matter to products stored in glass or plastic bottles. However, it is one of the controlled factors as outlined by the PCPC stability guidelines. 

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