Prepress verification of barcodes: connecting the dots
Prepress verification of barcodes is a common practice in many printing companies. The reasons are partly from experience and partly practical: verification at prepress catches problems before they waste expensive press time, keeps expensive verification out of the damage-prone press environment and keeps press operators from making decisions they shouldn’t make based on technical and confusing verification reports.
Prepress verification of barcodes is a common practice that creates a gap in quality assurance
These and other reasons have inadvertently created a virtual gap between the prepress and on-press operations at some very large and successful companies—and this has contributed to some problems and stresses in those companies.
It often sounds like this:
My team in prepress receives the files from the customer and we quality-check it. We fix any problems we find and send it to proofing where we verify the barcode and send it back to the customer for approval. When everything is signed off, we send it to printing and everything should be fine. But sometimes everything isn’t fine—there’s a problem with the barcode. How can this happen?
The rationale for prepress verification makes sense. Prevention is definitely better than remediation of barcode problems, considering the potential liability and cost of a barcode failure in the retail channel. But prepress verification can only check for a limited set of attributes and therefore can only test for a limited number of problems.
Prepress verification can only test for a limited set of barcode problems
The proof image of the barcode is not the same as the press image. The pigment is different, the substrate is different and the method of applying the pigment is different. If the data file has been compensated for press gain (bar width reduction) the proof image will likely be thin; the press image thicker. If the bar width reduction factor is insufficient for the press, it will probably seem perfect for the proof, where gain is usually much less—and in any case, different than the press.
Proof color is not always an exact match to the press. An acceptable proof color may not be acceptable on press.
This begins to describe the gap between prepress and on-press. There could be myriad other factors as well—for example a press with a digital head for sequencing barcodes in a variable printing job.
What can be meaningfully tested on a barcode at prepress? Some very important attributes: symbology—making sure the barcode is the right kind; check digit correctness, quiet zones, and validation—make sure the human readable match the encoded data and make sure your customer agrees that this is the right code for this product.
Prepress verification is not a fallacy–it’s just not the whole story
Prepress verification is not a fallacy; it’s just not the whole story. Prepress is planning for the future: on-press is the present reality. It would be overstated to say that on-press is all that matters, but it is no exaggeration to say that on-press is the last best place to verify barcodes.