The moments when an old test result stops being good evidence
An old test result for a lunch container stops being good evidence when the material, supplier, shape, or use changes, because the result describes the container that was tested, not the container now being sold.
When does an old result expire?
A test result has a shelf life, even though it rarely carries an expiry date. For a plastic lunch container, a result obtained for one material, from one supplier, in one shape, describes that container at that time. When any of those factors changes, the result's relevance weakens, and the seller must decide whether it still supports the container now being sold, or whether a new test is needed.
Material change is the clearest trigger. A new plastic, a new colour masterbatch, or a new supplier for the same plastic can change warping, lid fit, and seal behaviour, even when the container looks identical. The seller should treat a material change as a retest trigger by default, and should record a reason if retesting is judged unnecessary, rather than assuming the old result still applies.
Which changes trigger a retest?
Shape and design changes are a second trigger. A wider mouth, a thinner wall, a new lid hinge, or a different seal profile can change how a container warps in a dishwasher, how it seals after repeated opening, and how it behaves when filled with hot food. A test for the old shape does not automatically cover the new shape, even if the material is unchanged.
Use changes are a third trigger. If a container originally tested for cold lunches is now marketed for hot soups, or if it is now sold for children who drop and squeeze it, the old test conditions no longer match the new use. The seller should compare the old test conditions with the new marketing and use, and should retest where they diverge.
Can retesting be selective?
Illustration: a seller holds a test report for 40 containers from an old material and imagines that 20 of them, in round illustration terms, would need retesting after a supplier change, because their lids differ. Those figures, as presented in The moments when an old test result stops being good evidence, are invented, not measured. They illustrate a practical point: retesting does not always mean testing everything again. It may mean testing only the changed feature, such as lid fit after a material change, while relying on the old result for unchanged features, with reasons stated.
That selective approach is legitimate only when it is written down. The seller should state which features were retested, which were carried forward, and why the carried forward features are unaffected by the change. Without that note, selective retesting looks like cherry picking.
How do you build a retest trigger list?
A retest trigger list helps a seller act consistently. The list should name triggers, such as material change, supplier change, shape change, and new use, and should state the action for each trigger, such as a full retest, a partial retest, or a documented review. When a trigger occurs, the list tells the seller what to do, rather than leaving the decision to memory or mood.
- List material, supplier, shape, lid, and use changes as retest triggers.
- Compare old test conditions with the current container and its marketing.
- Decide on full, partial, or no retest, with reasons written down.
- File the old result, the change note, and any new result together.
Why is retesting often delayed?
Retesting is often delayed because an old report feels reassuring and a new test feels costly. A seller who keeps citing an old report for a changed container may feel safe, while the evidence quietly becomes irrelevant. The cost of a retest should be weighed against the cost of a listing claim that no longer has evidence behind it, which can be far higher if a customer or authority challenges it.
Another delay comes from treating retesting as an all or nothing choice. A seller who believes a full retest is the only option may postpone it indefinitely, while a partial retest of the changed feature would have been quick and sufficient. Breaking retesting into features makes it manageable and more likely to happen.
How do you keep test evidence current?
Close by reviewing the container's test file at regular intervals, even when no change is obvious. Suppliers change materials quietly, production processes drift, and marketing expands into new uses, and a periodic review catches those drifts before they become evidence gaps.
When a retest is performed, keep the old and new results side by side, with a note explaining the change and the reason for retesting. That history shows that the seller's evidence evolves with the product, rather than resting on a single report from the past.
Sources and evidence on the record
- Regulation (EU) 2023/988 (GPSR), EUR-Lex - the general product safety regulation, applicable from 13 December 2024.
- CEN and CENELEC, CEN and CENELEC - European standards including harmonised standards.
Evidence basis: Official sources below frame this guide; the container example is general educational material, not a finding about any real container. Applies when: This guide applies when a seller whose supplier changed a material for a plastic lunch container needs to decide whether an old test result still counts as good evidence.