Corner Stains on a Carton: Rebuilding a Leak-Through Claim

Forty cases out of nine hundred arrived at a retail distribution centre with brown tide marks on one corner. The retailer rejected the pallet, the processor rejected the claim, and the pad supplier was asked to explain a failure that had nothing to do with absorbency. Six weeks and a lot of email later, the actual cause turned out to be a three-millimetre crack in the base of one tray, moulded in the same cavity as two hundred others that were fine.

Leak-through claims are almost never about a pad that could not absorb. They are about fluid finding a path that the pad was never positioned to block. Rebuilding the path is the only way to settle the claim, and it is also the fastest route to preventing the next one.

The four paths fluid actually takes

First, edge wicking: the pad is narrower than the tray base, fluid runs off the product at the edge and down the tray wall instead of into the pad. Second, saturation overflow: the pad is full by hour five and the rest of the drip has nowhere to go. Third, tray damage: cracks, warped bases and worn corners that let fluid through the plastic itself. Fourth, stack transfer: fluid on the outside of a tray touches the carton below when trays are stacked, and capillary action does the rest.

Each path has a different fingerprint. Edge wicking stains the carton along a full side. Saturation overflow stains the centre of the base. Tray damage leaves a concentrated spot, often with a matching mark on the shelf. Stack transfer stains the top face of the lower carton, which is the one clue most people miss.

Documenting before you clean up

The instinct on discovery is to wipe the tray and repack. That destroys the evidence you need. Photograph the tray in place, before anything moves: the pad position relative to the tray edge, the fluid line on the tray wall, the stain pattern on the carton, and the tray base held up to a light. Note the batch code on the tray if it is moulded in, and the pad batch from the case label. Four photographs and two numbers will settle most claims in a day.

Then weigh the pad. A pad at forty percent of capacity rules out saturation and points at geometry or tray damage. A pad at ninety percent points at sizing. That single measurement splits the investigation in half, and it is the number a supplier will ask for first.

Fixing the path, not the pad

If the cause is edge wicking, the pad needs to match the tray base within five millimetres on every side, or the tray needs a raised perimeter that channels fluid inward. If it is saturation, the fix is a heavier pad or an earlier change, not a different brand. If it is tray damage, a five-second inspection at the tray wash exit catches most of it, and a light table catches the rest.

Stack transfer is the one that surprises people. A tray that looks dry on top can carry a film of fluid on its outside wall from the wash or from condensation, and that film is enough to mark a carton. A slip sheet between layers costs a few cents and removes the path entirely. In one beef plant, adding a perforated slip sheet cut carton claims by two thirds without any change to pads at all.

Worth adding to the file: the pallet’s own history. A carton stained on the bottom layer may have been marked three pallets ago and only noticed now, because the mark develops slowly as moisture migrates through the board. Date the photographs and keep the pallet id, or a genuine one-off failure will look like a systemic problem by the time it reaches a buyer.

Next time a claim lands, resist the urge to test the pad first. Walk the tray, photograph the path, weigh the pad, and only then look at the specification. The pad formats and tray-fit options cover most of the geometry fixes, but the crack in the mould is yours to find.