Paper cup leak test timing adds useful evidence when a cup looks dry at first but becomes wet later. A pass-or-fail total hides when and where the first sign appeared. Recording both can help separate an immediate forming defect from delayed wetting or a misleading spill mark.
Use the buyer-approved liquid, fill level, temperature, exposure duration and acceptance criteria. This diagnostic record is not a substitute for a validated packaging test or food-contact compliance assessment. No universal holding time or temperature is implied.
Diagnostic decision table
| First observation | Investigation branch | Evidence to retain |
|---|---|---|
| Wet mark immediately after filling | Seal opening or filling spill | First location and filling record |
| Slow wetting near a cut edge | Edge exposure or barrier continuity | Wet-front progression |
| Leak appears after handling | Mechanical disturbance | Handling event and prior condition |
| No leak before the test ends | Survived the observed period only | Actual observation duration |
Define the first-failure event precisely
Agree what counts as failure before filling the samples: an external wet mark, a visible droplet, a liquid path or another defined criterion. Distinguish appearance observations from the final acceptance rule. Different inspectors may otherwise record different failure times for the same cup.
Start the observation clock at a defined event, such as completion of filling. Record each sample separately if filling takes appreciable time. Use the agreed safe handling method for hot liquids and stable sample supports. Prevent rim spills from running down the outside and masquerading as sidewall leakage. Mark and exclude a documented handling accident according to the test plan.
Create a repeatable location map
Use the sidewall seam as the angular reference and identify the rim, seam body, seam-bottom junction and remaining bottom circumference. Number the cups before filling without contaminating the test area. A photograph of an isolated wet patch is much less useful than a photograph showing its relationship to the seam and base.
Observe from a fixed position where possible. Record the first location before the liquid spreads across the support surface. If an absorbent indicator is used, define its placement and recognize that it may draw liquid away from the original point. Do not assume the largest wet area is the point where the leak began.
Preserve timing uncertainty instead of inventing precision
If samples are checked at intervals, record the last dry observation and the first wet observation. The failure occurred within that interval; reporting the latter timestamp as an exact physical failure time overstates the evidence. Continuous video can narrow uncertainty when the first visible event is clearly defined and visible.
For cups that remain dry, record the completed duration. They did not fail during the observed period, but their ultimate failure time is unknown. Do not enter the end time as a failure or claim indefinite resistance. Keep these samples distinct when comparing trial groups, particularly if the groups were observed for different lengths of time.
Compare groups with matched conditions
Group samples by material lot, tooling or station identity, recipe and production period. Keep liquid, fill level, inspection interval and handling comparable. Compare both the proportion failing by the agreed endpoint and the location pattern. A group with fewer failures but a new recurring seam-bottom defect still deserves investigation.
Use the map to request a targeted machine review. A defect concentrated at one junction suggests a different next check from broad delayed sidewall wetting, but the location alone does not prove a cause. Retain unused blanks and unopened finished cups from the same run so the material and forming histories can be investigated independently.
Close the investigation with a controlled confirmation
Document the proposed cause and the single approved change intended to address it. Repeat the same observation method on a new identified run. Preserve the original results, including failures; replacing them with only the successful retest prevents a reviewer from judging whether the pattern actually changed.
Send HANNAI the sample table, seam-oriented photographs, material construction and test conditions. Include whether the failure occurred before or after handling and how its time was determined. This evidence allows support to distinguish a forming-station inspection from a material or test-method review without guessing a temperature correction from a wet cup photograph.
Related equipment and next checks
Review the paper cup forming configuration and the related guide to paper cup leakage inspection. The Engineering Notes archive connects these checks with wider machine planning.
Frequently asked questions
Is the first wet inspection time the exact failure time?
Only if the event was continuously observed; otherwise record an interval.
Does a dry cup at the end prove unlimited resistance?
No. It establishes only the completed observation period under those conditions.
Should spilled samples be counted as leaks?
Identify the handling event and apply the agreed test-plan rule.
Can leak location alone identify a faulty machine component?
No. Combine it with material, station and trial evidence.
Review the evidence with HANNAI
Send your machine model, component identification and the observations described in this guide. Include the drawing or material reference and any before-and-after measurements so the required next check can be identified.