Poor label placement
The most obvious culprit of an unreadable barcode is poor label placement. Imagine wrapping a 1D barcode label around the circumference of 15 mL tube. Now take a scanner and try reading the barcode. There’s no way the laser emitting from the scanner can read all the lines of the barcode if it’s wrapped around the tube. Unfortunately, samples that are labeled by one user are frequently analyzed by another later down the road (a nurse who takes a blood sample and delivers it to a medical lab to be processed, for instance), making it difficult for lab personnel to control how samples are labeled.
Solution: The best way to avoid a poorly placed barcode is to have a standard operating protocol (SOP) in place that specifies an appropriate methodology for each container that requires labeling, including the type of label, barcode, and label placement. When designing your SOP, be sure to include pictograms that make it clear how each type of tube is supposed to be labeled.
Poor barcode/scanner position
A failed barcode scan can be caused by a few things related to the position of the barcode or scanner:
- The barcode might be too close or too far from the scanner, depending on the scanner’s optimal focal distance (the distance at which the barcode comes into focus).
- The barcode might be located at a poor angle relative to the scanner. Mounting a scanner perpendicularly to the barcode can cause specular reflection, where light is reflected directly back at the scanner, blinding it to the signal of the barcode.
- The orientation of the barcode might not be compatible with the scanner. For example, laser barcode scanners must be placed such that the laser line is perpendicular to the bars of the barcode for it to be read.
Solution: For applications requiring challenging scanning conditions, using readers with built-in autofocus is ideal, as they can adjust to a range of variable barcode distances, angles, and orientations. Employing barcode imagers instead of barcode scanners, which use cameras to read images of codes rather than the signal of the reflective laser, may also be helpful as they are less liable to suffer interference from the reflecting laser and can often read barcodes no matter the orientation. Right-angle mirrors can also reflect the light of the barcode towards the scanner; however, when using right-angle mirrors, it’s important to have a scanner that can read flipped images.
Damaged barcodes
Barcodes can be exposed to many harsh conditions, such as extreme temperatures and chemical exposure. This can make your barcodes fade or smudge, causing them to become unreadable. Barcodes can also suffer from mechanical damage, like scratches, tears, or crinkling.
Solution: Here is where choosing the right label is crucial. Using a label that’s appropriate for your application will not only make sure that it stays affixed to your container, but it will also prevent damage to the label (and barcode) from the harsh environment(s) it encounters. Remember, prevention is always worth more than a cure, especially when it comes to physically damaged labels. This also applies to the printout; not all types printouts will protect your barcodes. Thermal-transfer printers provide your labels with the greatest resistance against extreme temperatures as well as organic solvents and other chemical substances, ensuring your barcodes won’t smudge or fade over time. For the times where physical damage is unavoidable, some high-performance readers can utilize symbol reconstruction technology, which allows them to reform the original barcode from the scan lines that are still intact. Varnishing or laminating your labels will also help protect your barcodes from scratches and other damage.
Insufficient contrast
To properly read a barcode, the scanner must be able to differentiate between the light and dark features of the symbol. However, the contrast between these two elements can vary depending on the type of material the barcode is printed on (e.g. thermoplastic film labels might provide more contrast than printing on metal). The contrast might also be affected if the printed bars—or the surface they’re printed on—aren’t uniform across the entire barcode. If there isn’t enough contrast, the scanner won’t be able to properly distinguish the marking of the barcode, making it impossible to read. Low-contrast barcodes will also reduce the distance at which a barcode can be read.
Solution: Adjusting your printer settings to ensure that ink is distributed evenly across your label (or other surface) is a good first step to avoid low contrast barcodes. It’s usually the surface, though, that’s the problem. Enhancing the brightness/contrast of the barcode is the best way to deal with low contrast due to uneven or noisy surfaces. Some barcode readers are designed with extra lighting features that, depending on the surface, can employ either diffused lighting (for glossy, flat surfaces) or dark-field lighting (for embossed or engraved barcodes) techniques to read barcodes.
Quiet zone infractions
The quiet zone, or no-print zone, is the area around the barcode that’s completely free of markings. This zone makes it possible for the reader to verify the boundaries of the barcode and scan it in its entirety. The quiet zone has specific requirements that depend on what kind of barcode you’re using. For 1D barcodes, the quiet zone should be at least 10 times the width of the smallest bar on both the right and left ends of the barcode. For 2D barcodes, each type has its own requirement, but it’s usually recommended that the quiet zone on each side of the barcode be at least 10% of either the height or width (whichever is smallest) of the symbol. On many occasions, however, markings can bleed into the quiet zone, making the scanner fail to read the barcode appropriately.
Solution: Adjusting the settings of your printer to ensure that the quiet zone requirements for your barcodes are met is the simplest solution. Because there is no maximum amount of space for quiet zones, you can always increase their space past the minimum requirements to make sure the barcode is read properly. If the printout frequently bleeds into the quiet zone, you’ll want to ensure your printout isn’t smudging. Again, using a thermal-transfer printer for your barcodes is ideal, no matter the environment.
Inconsistent printout
There are many reasons your printer isn’t reliably rendering barcodes. For digital printers (inkjet and laser), low ink and toner levels are the main cause of barcode inconsistency. If the ink or toner levels are too low, your barcodes will suffer, as the intensity can start to fluctuate (some printers will even stop you from printing if the ink is too low, but this is undesirable as well, since there could be up to 40% of the cartridge left over. You might also have any number of problems, from your ink not sticking to your label to printer jams and air bubbles in the cartridge.
Solution: Using a thermal-transfer printer solves many of the issues related to inconsistent printouts from digital printers. They employ wax and/or resin ribbons, giving a more uniform printout right until the very end of the ribbon. With that said, it’s important to continuously verify the settings of your printer and to properly maintain it. The distance between the printhead and your labels, as well as the integrity of the printheads and the nozzles, should be checked regularly. For those using laser printers, a simple trick is to switch the “Media/Paper Type” in your print settings to “Label” or “Thicker Paper” instead of “Plain Paper” in cases where the ink isn’t adhering to your labels.
Inappropriately programmed scanner
When programming your scanner, limiting the number of acceptable digits in the data field can make any barcode fail to scan.
Solution: Check your scanner and the requirements of the type of barcode you’re using! Some symbologies, such as Code 39 and Interleaved Two-of-Five (ITF), encode 13 digits, not 12, and may require some toggling for your scanner to properly read them.
Other considerations
A few other points to consider is the density of the barcode and the software that you use to print them. Trying to encode too much information will result in a high-density barcode, where the narrow white spaces between bars become too narrow to be detected. Using a barcoding software will help to avoid this issue, while also ensuring you print high-quality customizable barcodes.
It’s crucial that barcodes are read in a timely and consistent manner, no matter where you work. Unreadable barcodes can grind your workflow to a halt, especially for industries with regulations on inventory and production, including pharmaceutical, biotech, and medical device companies. Unreadable barcodes can also result in the loss of information associated with patient samples. When employing barcodes, it’s important to use ones that have been verified and conform to ISO standards. Verification means assessing and grading your barcodes before they’re employed in your operations. Using verified barcodes will make it much more likely that they’ll be read consistently and will help save you precious time and money fixing ones that don’t scan.
LabTAG by GA International is a leading manufacturer of high-performance specialty labels and a supplier of identification solutions used in research and medical labs as well as healthcare institutions.
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