On stability philosophy & separations...

Dear all,
Background: at our factory we focused in recent years mainly on shampoos & hair products, recently we are trying to step into creams, light creams and lotions. For this discussion, im interested mainly on  your stability opinions -

On its way to the incubator - Every sample is being fully loaded to it's cap, and after a day insereted to a 40C incubator. However - tests fail regulary about about 7 - 14 days.

I see a lot of flocculations, sometimes creaming, bubles forming, etc, but mainly on my lighter creams.
Sometimes- formuals that sit stable on my bench for a year - are being separated after 10 days in the 40C incubator.


my questions - regarding 40C stability oven:

1. I sense that 3 months testing for creams/ lotions is too much. I am sad to say i never reach that. (I barely reach 1 month with my light cream shonestly...)
how much time passes for your creams/ lotions after you reach a conclusion that its "good enough" lets say for 3 years expiry? 

2. Do you let creams "settle" for 1-2 days prior insertion to the incubator to increased stability? does it even matter?

3. Is humidity control is crucial for cosmetic formulae stability tests? our incubator is a "dumb" thermostat type without humiditiy control - and i sense always theres a water layer above the samples, after several days. is it connected to humidity not being controlled?

4. is it known that lotions and creams are "more gentle 

5. This is the trickiest one: what - for you -are the "allowed phenomenons" that happen to a sample while in stability, that don't disqualify your stability test? 

= = = = = =
We regualry use 70-75% water,
Xanthan Gum 0.3% 
Sepimax Zen (acrylate corsspolymer-6) about 0.4%~
Cetearly alcohols - 3-4%
Diffrent oils, about 3-5%
and mainly GMS-SE / Neutralized stearic acid/ other emulsifiers 3-6%

Thank you in advance for those who will assist!

Comments

  • And your preservative system is?
    Cosmetic Brand Creation. Concept to name to IMPI search to logo and brand registration. In-house graphic design inc. Pantone specs. Cosmetic label and box design & graphics.
  • ozgirlozgirl Member, PCF student
    You definitely need to improve your emulsion stability or you will run into trouble. I am not sure where you are located but in many parts of the world temperatures regularly exceed 40oC especially during transport. It would not be good if customers receive a product that has already separated because the temperature was high during transport.

    If you post a complete formula for just one of the products that you are having trouble with you may get some help.
  • jeremienjeremien Member
    edited January 2019
    Emulsion are thermodynamically unstable... so of course it will follows a destabilization pathway with time. You need to be sure that your especification are not too strict. Maybe flocculation, if it is weak flocculation is not a "no go"  after 1 month at 40ºC.
  • PerryPerry Administrator, Professional Chemist
    Where I worked if there was any change in the formula outside of specifications it was a stability fail.

    What you describe sounds like a failure to me. Especially since the product will likely experience temperatures over 40C at times during storage in a warehouse.

    Ultimately, it is up to you to decide what changes are acceptable. If it fails microbial stability then nothing is acceptable. If the changes are aesthetically different, then your customers may not care.
  • thanks all - so what you're trying to tell me is that you definitly saw and worked with lotions and light creams that sat aprox. 2 months at least at an incubator - and barely changed ? 
    no inner bubbles, no top humditiy forming, the same as inserted (setting aside perfume / color slight changes)

    what abut the need for humditiy being constant at stability checks?
  • PerryPerry Administrator, Professional Chemist
    The chambers we used were humidity controlled but I think in most cases, it won't matter.
  • First, you need to determine if it's the preservative or the emulsion that is failing.
    It looks like it's the latter, but only further testing can confirm that.
    i.e. you may make an identical formula with lots of "high power" preservatives (i.e. parabens) and see if it still fails.
    Then you can switch to using more/different emulsifiers and see if it works.
  • I see Gunther, that is a good idea and ill check it
    However - i still want a take home message: how can it be that a lotion that sits for a year on my desk - stable and looking very good-   is being separated after 2 weeks in the oven?

    is it even a good practice to always check lotions in an oven?
    can't a centrefuge tell another story aswell?

    what is the verdict, lets say, to a lotion that separates in 2 weeks in the oven, but is stable after centrifuge?
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