A wallpaper glue complaint without lot identity, samples and use conditions usually produces assumptions rather than a defensible answer. A useful traceability system connects the factory retain, buyer receiving sample, local repacking sample and customer return to the same production lot and compares them under controlled conditions.
Define the four sample positions
The factory retain represents production release; the buyer receiving sample represents the condition after transport; the repacking sample checks the local packing process; and the customer return records the disputed material. Label each with product, lot, sampling date, location, package condition and custodian rather than only the product name.
Carry lot identity through repacking and sale
When a 20kg bag becomes retail packs, the original production lot must map to the new retail code, repacking date and line record. Mixing original lots into one repacking batch prevents a narrow investigation and may force the buyer to hold more inventory than necessary.
Record actual use conditions
Alongside photographs and order information, record water source and temperature, ratio, addition order, mixing and rest time, ambient conditions, wallpaper type, substrate preparation and time since the bag was opened. These variables influence lumps, dissolution, viscosity and workability and cannot be ignored when assigning cause.
Run matched comparison tests
First reproduce the customer conditions, then test the factory retain, receiving sample, repacking sample and return under the TDS or agreed standard method. Reproduction explains the field event; the standard test compares the materials. Preserve weights, times, temperatures and instrument settings for both stages.
Write an actionable conclusion
The report should state the evidence, affected lot, temporary quarantine scope, additional tests and any cause that remains unconfirmed. Avoid replacing analysis with a simple pass or fail label. Hangzhou Karn can help verify factory lot and document records, while the buyer must preserve local repacking, storage and application evidence.