Freezing and heat

A water-based product spends its life in uncontrolled temperature, and both extremes have their own failure.

Both ends of the delivery van

A parcel in January and a parcel in July are different environments, and a formula stable at room temperature can fail in either.

The customer sees the result and attributes it to the product.

Freezing

Water expands on freezing, which stresses a full bottle and can split a seam or pop a closure.

Components drop out of solution: a cloudy product, sediment, or a gel. Many redissolve on warming and plenty do not.

Emulsions break, usually permanently.

And a thickened product can gel irreversibly.

The test is a freeze-thaw cycle, several times, rather than a single freeze, because it is the cycling that does the damage.

Heat

Accelerates every degradation: fragrance loss, color change, pH drift, container attack.

Increases internal pressure, which shows as a swollen bottle or a leaking closure.

Reduces viscosity, sometimes permanently.

And where there is any gas-producing reaction in the formula, heat is what turns a slow one into a visible one.

Testing for it

Three freeze-thaw cycles, and a sample held warm for several months.

Look at clarity, viscosity, pH, smell, color and the container after each.

Weigh the warm samples, because weight loss is the earliest container signal.

And decide what the label says. A freeze warning and a storage instruction cost nothing and they move the conversation from a defect to an instruction, but only if the product genuinely recovers, and saying so when it does not is worse than saying nothing.

References