Barcode Killers

Barcodes are forgiving of a wide range of inaccuracies. The experiential evidence alone validates that: how many times in recent memory have you encountered a barcode that did not scan quickly—or at all? Probably few times if at all. The quality control attributes also bear witness to the robustness of barcodes. Most of the print quality parameters are graded; they have a tolerance or range of acceptability within which the barcode should perform. Only a few parameters are pass/fail with no margin of error. Those are the potential barcode killers.

Quiet Zones

The quiet zone are an unobstructed area around the barcode. This helps the scanner to find and identify the barcode. Scanning technology utilizes reflective differences to decipher a barcode, so extraneous reflective differences, in the form of text or graphics, can confuse the scanner.

Violated or encroached quiet zones are a common cause of barcode failure. On a 2D symbol like a QR or Data Matrix code, quiet zones are included in the Fixed Pattern Damage parameter.

Print Gain

Print gain is another common cause of barcode failure. This is the result of ink spreading during the printing process. There are many potential causes:

• Physical pressure exerted on the printing plate against the substrate
• A porous substrate that the ink wicks into
• Surface tension when two or more inks come into contact with each other
• Failure to compensate the printing plate or design file (bar-width reduction)

Printers are generally aware of the causes of print gain, but there are situations that contribute to unclarity about bar width reduction. Driven by a desire for data control and security, some companies provide the barcode design file to their printer-contractors. All print processes need consider print gain, and most of them will require some level of bar width reduction. Determining the amount requires some testing as well as some process control. Without this, the printer must use uncompensated or incorrectly compensated files to produce working barcodes. When they cannot, the customer often fails to understand that their own practices have created this untenable situation for their vendor.

Other Barcode Killers

Scanners decode a barcode by detecting the reflective difference between the barcode and its background. The difference is measured and graded by the ISO parameter Symbol Contrast. The optimal symbol contrast is a black barcode on a white background, but other colors are also used. Reds and greens are the most problematic, because scanners are required to use a red light source. Thus reds are indistinguishable from white, and greens are equivalent to black. A scanner simply cannot see a red barcode on a white background, or a black barcode on a green background.

Questions and comments are welcome. Contact us here.