Tips & Tricks: Scratches on Folding Box Packaging

Outline and impact of problem
Printing products must exhibit a certain amount of resilience against the mechanical forces of the printing process, finishing work, and transport. Printing stock surfaces, the printing ink used, and the inline coating applied all play roles. When transporting printed materials for further print processing or to the end-customer, it is important that they be sufficiently protected so that no damage comes to the print stock surface, the printing ink, or the coating layer.

Challenge and solution
A coating that is not optimally applied can result in damage to surfaces during handling or transport. This is why it is important to choose the correct varnish, and to adopt appropriate controls during the printing process. Test coatings should be performed in doubtful cases when starting on a new order.

Case Study
The contents of a pharmaceutical product were poured into 0.2 liter glass bottles (6.75 ounce) and sealed. After being transported by truck, the recipient refused delivery citing pronounced scratch marks on the folding boxes. FOGRA was sent the rejected packaging, unprinted cutouts from different production runs, printing ink, and varnish samples to investigate.

Visual Evaluation of the Rejected Folding Boxes
The folding boxes, protected by an aqueous coating, showed very clear scratch marks in various spots, as seen in illustration No. 1. Numerous furrows can be seen, which partly peel back the varnish and printing ink surface, as well as the coating on the cardboard. These observations indicate that the damage occurred either because the cardboard surface was too soft, or because of some aggressive contaminant.

Abrasion Test on the Folding Boxes
An abrasion gauge was used to run a comparative abrasion test on samples from the rejected batch and on samples from earlier production runs. In every instance, the printing ink and varnish bonded sufficiently for an aqueous coated product. No differences could be established between the rejected production run and earlier productions.

Imaging with the Scanning Electron Microscope (SEM)
One of the glittering particles was imaged using SEM. Illustration No. 2 shows a hard and smooth-surfaced particle, still partially embedded in cardboard. The form of the embedded particle indicates that this could be a glass splinter from one of the filled bottles. In order to confirm this suspicion, glass splinters from one of the bottles in the delivery were imaged.

Conclusion
The tests showed that the folding box prints for aqueous coating demonstrated a normal resistance to abrasion. Results were identical in both the earlier, acceptable delivery and in the rejected delivery. The hard particles observed in some cutouts, are embedded glass splinters apparently originating from the packaged bottles. The freedom of movement between individual packings plays a large role in cases where released particles can be dispersed.