What you are seeing
The code prints on the wrong stock: a glossy sheet when you needed matte, a thin paper when you needed card, a coloured stock when you needed white, or a label stock that does not suit the printer. The wrong paper changes contrast, drying, sharpness, and durability, so a code that scans on the right stock can fail on the wrong one. The cause is usually a tray mix-up, a stock substitution, or a job ticket that never named the stock. The fix is to confirm the stock before the run and to reprint on the correct material.
Likely causes
1.
Wrong tray or stock loaded — A printer with several trays can pull the wrong stock if the tray selection is wrong. Test: check the stock in the tray against the job ticket.
2.
Stock substituted without notice — A supplier or colleague can substitute a similar-looking stock that behaves differently. Test: compare the used stock with the specified stock.
3.
Job ticket never named the stock — A job with no specified stock gets printed on whatever is loaded. Test: check whether the job ticket names the stock.
4.
Stock unsuited to the printer — A stock that does not suit the printer can smudge, fade, or reflect. Test: check the stock against the printer's recommended media.
5.
Stock unsuited to the environment — A stock that suits the printer can still fail outdoors, in damp conditions, or under handling. Test: check the stock against the conditions where the code will live.
Step-by-step fix
1. Identify the stock that was actually used and compare it with the specified stock.
2. Check the printer tray selection and the job ticket.
3. Choose the stock the job requires for its printer and its environment.
4. Print one proof on the correct stock and scan it on two phones.
5. Update the job ticket to name the stock, the tray, and the print settings.
6. Reprint the run on the correct stock and spot-check the first copies.
Putting this into practice
In practice, the job ticket is the fix. A ticket that names the stock, the tray, and the print settings prevents the tray mix-up and the silent substitution. A ticket that says print it leaves the stock to chance, and chance picks whatever is loaded. Keep a short note of what you tested, what failed, and what you changed, so the next person starts from evidence rather than guesswork. A fix that is written down survives staff changes and reprints; a fix that lives only in memory gets repeated.
Common mistakes to avoid
- Leaving the stock off the job ticket and discovering the run was printed on whatever was loaded.
- Reprinting the full run before a single proof passes, which turns one failure into many.
- Testing on one phone in ideal conditions instead of two phones in the real conditions where a code that prints on the wrong paper will be used.
- Changing the artwork and the placement at the same time, so you cannot tell which change fixed a code that prints on the wrong paper.- Skipping the proof test because the change looked small, when small changes cause most repeat failures.
Quick checklist
- The stock matches the job ticket
- The stock suits the printer and the environment
- The proof on the correct stock scans on two phones
- The corrected proof passes on two phones in the real conditions
- The fix is recorded in the job file so the next reprint starts from a proven setup
- Every printed copy is checked against the approved proof
- The proof is retested after any later change to the link, design, or placement
Related tools and guides
- [QR minimum size checker](/qr-minimum-size-checker)
- [QR contrast checker](/qr-contrast-checker)
- [QR print proof checklist](/qr-print-proof-checklist)
- [QR DPI calculator](/qr-dpi-calculator)
- [QR quiet zone calculator](/qr-quiet-zone-calculator)
- [printed QR tester](/printed-qr-tester)
- [QR size calculator](/qr-size-calculator)
