Stability Testing

Stability testing stores samples of a product under controlled conditions and tests them at intervals to establish how its properties change over time. It is how a shelf life is determined, rather than estimated.

Real-time testing stores product under normal conditions and tests it periodically across the intended shelf life - the most reliable method, and the slowest, since claiming two years requires two years. Accelerated testing stores samples at elevated temperature to speed up degradation, allowing an earlier provisional estimate. Accelerated results are indicative rather than definitive, because raised temperature can trigger changes that would never occur normally, so real-time work usually continues alongside.

What is measured depends on the product's likely failure modes: separation in an emulsion, viscosity drift, colour change, loss of active concentration, pH movement, or packaging interaction. Testing in the actual container matters, since a product can be stable in glass and unstable in the plastic it ships in.

For a new product this is a genuine lead-time item that runs in parallel with other work rather than after it, and it is worth starting as soon as pilot material exists. Stability data is also usually required for regulatory submissions.

Start stability work as soon as pilot material exists, rather than after production is established. It runs on its own timescale regardless of everything else, so beginning late delays a launch in a way that no amount of manufacturing speed can recover.

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