Interpreting result from stability test

Sample of a face cream was created and divided into two containers for stability test, one at room temperature and one at 45oC. The one at room temperature remains unchanged after 2 months while the other one darkens in color and thickens as well. Both had PEG-80 and xanthan gum added. Does this result imply that the product will eventually darken in color and thicken up over time or will this only occur under high heat? The one that stays in room temperature is totally fine, no changes since mixing. Scent, viscosity and weight remain the same.


  • Was there any water loss for the product that was in the 45? 
  • PerryPerry Administrator, Professional Chemist
    Yes, that is the idea. Increased temperature increases the speed of chemical reactions.  But it is not an exact science and it's possible that you won't see those effects in the room temperature sample even after a year.  However, you should assume you will.
  • MicroformulationMicroformulation Member, Professional Chemist
    In my experience, this change in an organoleptic benchmark (change in color) would be a presumed failure due to an OOS result. Microformulation Cosmetic Consulting provides Custom Formulations for both large Commercial accounts as well as smaller entrepreneurs. We can provide Naturally compliant Formulations under the NSF, NPA, Whole Foods and USDA Organic Certifications. BS.Pharm Albany College of Pharmacy, Union University.
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