Labeling of consumer products is not only required by regulatory bodies for product identification, but it also serves as a symbol of product quality and prestige. Bubbles under the label are unsightly and impact customer satisfaction. Pressure Sensitive Adhesive (PSA) labels currently make up more than eighty percent of all labels in the market today, yet little research could be found addressing causes of bubbling in an industrial setting. A root cause analysis for bubble development included four aspects: label application, environmental conditions of shipping and storage, defects in glass bottle geometry, and oil contamination. The most significant findings from each area were as follows: Label Application. Force and contact time were confirmed to be significant factors in reducing label bubbling. The equipment settings directly related to these factors should be controlled and monitored. Environmental Conditions. None of the environmental conditions caused growth or appearance of additional bubbles as was the hypothesis. All 4 test conditions had a significant Paired T-test but in the reduction of bubble size. Glass Defects. A random sample of bottles showed very poor capability of the bottle dimensions. However, low capability to produce within specification limits does not necessarily lead to bubbling. A direct comparison test was done to compare diameters and variation from bubbled bottles to non-bubbled. No measurements that could reasonably be related to bubbles caused by glass defectiveness were statistically different. Oil Contamination. Initial data analysis showed that certain oil types had a higher chance of causing bubbling. However, after a controlled experiment was performed, the results were inconclusive that oil contamination pre or post-labeling could cause bubbling in isolation. The experiment did confirm the importance of sufficient pressure in the label application process.





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PSA, labels, essential oils, bubble defects



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Engineering Commons