What Are Glass Container Finish Defects?
By: Berlin Packaging Specialist
Several defects can occur during the manufacturing process of glass containers. Here are some common examples of glass finish defects, such as chipped finish, overpress, and split finish.
Seam Under Finish defect is a seam ≥ 0.5 mm situated on the joint between the finishing mold ring and the blank molds.
Out of Vertical Finish defect occurs when the finish axis is not aligned with the body, even though the finish and body axes are parallel and vertical.
Depending on the defect severity, sealing may be affected. Bad grip with screw and champenoise (wired cork) finishes. Trigger or breaking of the closure bridges.
Folds on the Finish defects are vertical or horizontal external marks on the finish, purely an aesthetic defect.
Glass Trimming on External Finish defect is a protruding ridge of glass around the upper part of the finish (thin rim of glass) > 0.2 mm.
Defective corking: risk of glass inside the bottle during recorking.
Folds Inside the Finish defects are vertical marks inside the finish.
Defective corking; risk of leakage.
Bulged Finish defect is a protuberance on the inside of the finish, which can affect the finish during uncorking; no risk of scratching.
Depending on the severity, it may affect the corking (bidule, for example) or the filling level.
Bent Finish defect occurs when the vertical axis of the finish is at an angle to the vertical axis of body.
Serious defect in screw, crown and twist-off finishes, less important in cork finishes.
High Finish Seam defect is a seam of glass ≥ 0.2 mm on the joint between the two sections of the neck ring mold.
Unfilled Finish defect occurs when the finish is not completely regular; the thread profile has not been formed properly. There is glass missing from the top surface.
Defective sealing: risk of leaks, product deterioration, problems in vacuum filling. Sometimes this can be just a minor defect (m), for instance unfilled finish on the bead of a cork mouth.
Rolled in Finish defect is an entry slough or extra thickness of the glass inside the finish.
This defect can result in defective corking.
Offset Finish defect occurs when the offset is at or greater than 0.3 mm.
Screw Pressure closure: bad sealing, risk of leakage. Cork closure: risk of breakage during corking.
Overpress defect consists of excessive glass projecting upward from the inside edge of the finish. This is a critical defect in all types of finish.
Defective closure, risk of leaks, product deterioration (M+). Breakage of the overpress with risk of contamination (C).
Crizzled Finish defect consists of fine surface fractures on the top of the finish (mouth).
Defective closure: risk of leaks. Not dangerous with corks (M+). Risk of contamination (C).
Blister on the Upper Finish defect is broken or unbroken bubbles in the thickness of the glass on the finish.
Risk of glass particles inside. Risk of breakage during the heat treatment and sealing. Defective closure, risk of leaks, product deterioration.
Split Finish defect is a small vertical crack starting at the top of the finish and going downwards. This defect is difficult to detect because it does not reflect light.
Risk of breakage during filling and packaging; leaking of product.
Chipped Finish defect is a small fragment of glass chipped off the finish (scratched), sometimes not completely detached.
On the top defect presents problems for vacuum filling, bad sealing, risk of leakage and deterioration of the product. On the side defect presents risk of breakage during use.
Checks on the Finish defect is a small crack running from the top of the finish in a downward direction. It can be seen by looking at the light reflection while turning the bottle.
Risk of breakage during packing (corking, sealing).
Lump defect is a small glass protuberance on top surface of the finish, only in one point of the finish: ≥ 0.3 mm (M+) < 0.3 mm (m).
≥ 0.3 mm can cause defective sealing: leakage risk, product deterioration with crown or screw caps, risk of breakage on wired corking. < 0.3 mm is not very serious.
Checks Under Finish defect is a surface crack under the finish, at the joint between the finish mold and the preparatory mold.
Risk of breakage with carbonated or sparkling beverages and a wired cork.
Glass Trimming on External Finish defect is a protruding ridge of glass around the upper part of the finish (thin rim of glass) > 0.2 mm.
Defective corking: risk of glass inside the bottle during recorking.
Out of Round Finish defect occurs when the finish is not round.