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acceptable bottle imperfections


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Is there a generally acceptable amount of bottle rejects due to imperfections (cracks, etc.) in any given shipment?

There should be quality standards available from your supplier that manufacturer uses. Cracks are never acceptable and would not be considered a defect. The root cause may be a defect but a crack itself would be caused by contact or rough handling. Our glass container industry rates defects into 3 basic categories. Major - These would cause harm to the consumer; Minor - These will effect the way the bottle performs during production; Cosmetic - Visually the container doesn't look correct but defect does not effect container's use. Overall all defects, which there are far too many to list, generally should never exceed 1/2 of one percent of a total production run. This would not be your particular order unless your order included every bottle produced. Any good supplier should be able to determine what the cause of a crack was and determine if the root cause was a defect. If you would be interested in getting a hold of testing lab to determine your particular issue I would suggest getting a hold of the Glass Packaging Institute. http://www.gpi.org/

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I've worked in the glass industry for over 20 years. Even one cracked or chipped neck in a shipment, without indication that it was caused by damage in shipment, would result in rejection. The glass would be sent back for 100% inspection to ensure that there were no longer any chipped or cracked necks. This condition could occur as a result of poor molding or during tranfer from the mold to the conveyor. Cracks in the body are rarely found. This would only occur if the bottles were not properly annealed after production.

As for AQLs (acceptable quality levels) for defects; in cosmetic and fragrance packaging the AQLs are typically within the following ranges:

Critical Defect (can cause harm to the consumer): Zero Tolerance

Major Defect (effects functionality or ability to fill): 1.0-2.5%

Minor Defect (effects only the appearance): 5.0-6.5%

For the beverage industry I would expect that the Major and Minor categories would have slightly higher AQLs but Criticals are likely still Zero Tolerance. Other examples of Critical Defects would be "Shark Fins", razor sharp pieces of glass at the mold seams caused by incomplete mold closure, and "Bird Swings", a strand of glass inside the bottle attached on opposing walls, usually only seen in rectangular or oval bottles.

As for the other categories, like our friend from Brown Pkg. states, there are too many to list. As a glass decorator we do incoming inspections on all bottles coming into our facility and will reject on behalf of our customers.

Dave, if you have specific concerns about a shipment of glass you received, you can give me a call and I'll be glad to share my experience.

Dave Desai - Decotech

Tel) 973-879-7906

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