Stability Test Questions: do you test for UV exposure?

Hello, dear wizards of formulating chemistry. Question: if you are testing for stability, besides temperature, do you normally test for light exposure? Also, when a product says "keep in a cool, dry place" does it mean their stability test was different? And, finally, what are the circumstances for PET? It lasts for a month, so do they keep it warm and cozy or just room temp? Thank you!


  • MaxMax Member
    Hello, from my very limited experience:
    UV is not required as many cosmetics are sold in none transparent bottles. Now I tested some producs under UV, plain sun.... not always glorious! EDTA, BHA... are often the solution.
    Keep in cool.... refers only to the way the customer should ideally store the product. Stabilities are often conducted at 30 and 40 degrees with... I think 65 and 75% humility.
    For the PET, we get this done outside at the moment, but looking at the test, you would think that 30 degrees should be an obvious temperature. 
  • Thanks @max :)
  • PerryPerry Administrator, Professional Chemist
    We always tested for UV exposure, even in opaque bottles. It was more of a safety check but on a couple occasions the plastic reacted with the fragrance or the fragrance leached into to bottle. Mostly, there were only problems with UV when the package was a glass jar.
  • ozgirlozgirl Member, PCF student
    We do a basic UV stability test by putting the sample on the window sill. If your product contains a dye this is important because many dyes are not UV stable.
  • Thank you!
  • chemicalmattchemicalmatt Member, Professional Chemist
    Better yet, AV, make your own "black box" UV stability chamber. Get the black-light bulb from an aquarium supply store, some simple hardware and mildly crafty wood-work, paint, and voila! A light stability chamber. I do recommend testing certain products for this too: especially ones with CI colorants, botanical extracts, terpenols, etc. Not uncommon to see discoloration after a few days in the box.
  • svensven Member
    @chemicalmatt interesting concept 
  • Awesome, thanks for the idea, I'll add it to the list of instruments to build for the lab :)
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