Do Your Products Perish from Hotness?

Published on by

Do Your Products Perish from Hotness?

Stability Testing 101

This summer in Australia is proving to be a hot one and as I sat here roasting over Christmas I was reminded of a product that I'd left out on the table to defrost after a couple of freeze/ thaw rounds a couple of months ago. Let's just say that it's not only people who perish from hotness...


The product in question was a water-in-oil cosmaceutical cream. I had decanted it into a black pot and left it out on my back yard table for the day while I headed off to a meeting. Not being my usual practice I forgot all about it until I got home some 6 hours later and that was when I noticed. The pack was almost melting it was so hot and inside the pack was what could only be described as a sloppy mess. The formula had failed!!!!

Unaccustomed as I am to product failure (in my dreams) I nearly cried when I saw this baby as I was sure that I'd created what could only be described as Gods gift to water-in-oil cosmaceuticals and so I put together a product revival SOS plan and waited.

Sure enough after a tense 24 hours of pretty much just leaving said product on my side board while I got on with other things I re-opened the pack only to find that it had magically gone back together again and what's more it stayed together in the week that followed - something that is not always a given as emulsions can break down to a point where there is no turning back.If you want a visual just leave some milk on the side in summer and watch what happens? Curdled mess with water on top? Now you're talking!

So, I wondered do ALL cosmetics fail on hot days or is this a case of 'formulation specific heat failure'? Time to do some research!

Cosmetics DO have optimal operating conditions above and below which problems can start to occur:

  • The product form may change making it thicker or thinner.
  • Form changes may lead to product spillage, over-dosing or failure to extract product from the packaging.
  • Product may break down irreconcilably (emulsion stability)
  • Colour may bleed, fade or change.
  • Products may get stickier to the touch or even start to feel stringy.
  • The product may split into two phases temporarily before re-gaining its structure upon temperature normalisation.
  • Actives within the formulation can start to break down (especially problematic for sunscreens)
  • Suspended particles in a product may drop or float out of suspension.
  • Aromas may disappear.
  • Preservative may stop working (most preservatives are only good up to 45°C, which can be exceeded, in a hot car on a summer's day.

It is possible for the cosmetic formulator to test temperature tolerance during stability testing and indeed it is part of the product validation to do so - it is no good stability testing a lipstick at 45°C when it turns to mush at 40°C or testing the spread ability of a balm at 5°C when it turns solid below 15°C. However, while products should be able to withstand a variety of 'in-use' conditions it is not practical to always have one formula to span the arctic through to the Sahara - car tyre makers can't do it so why should we?

The long and short of it is that product makers should pre-warn their public about how to store and use their product and in order to give the best advice a full, professionally carried out stability testing protocol is advised.Then it goes without saying that product users should read the pack BEFORE taking their cosmetic product on an extreme adventure into hotness land!

New Directions offers stability testing to suit a wide range of products with protocols ranging from 12-24 weeks.

Amanda Foxon-Hill

7 January 2013

More about: Stability Testing

This post has been closed; further comments cannot be added.