Guide to glass container defects

THERE ARE SIX BROAD CLASSIFICATIONS OF GLASS DEFECTS

1. Checks  

2. Seams  

3. Non-glass inclusions   

4. Dirt, dope, adhering particles or oil parks  

5. Freaks and malformations, and   

6. Marks 

      DEFECTS CLASSIFICATION  

• Critical, those that are hazardous to the user and those that make the container completely unusable.

• Major, those that materially reduce the usability of the container or its contents

• Minor, those that do not affect the usability of the container, but detract from its appearance or acceptability to the customer.

CRITICAL DEFECTS     AQL= 0.0

1. Stuck Plug. A piece of glass, usually very sharp, projecting inwards just inside the neck bore.

2. Freaks. Odd shapes and conditions that render the container completely unusable. Bent or cocked necks are a common defect of this type.

3. Choked Bore or Neck. Here excess of glass has been distributed to the inside of the finish or opening.

4.  Filament. A hair-like string inside the bottle.

5. Spike. Spikes are glass projections inside the bottle.

6. Bird Swing. Is a glass thread joining the two walls of the container

7. Soft Internal Blisters. A thin blister found in the internal surface of the glass container.

      FUNCTIONAL DEFECTS    AQL= 0,65

1. Check. A small, shallow surface crack, usually located in the bore or neck, under the finish, in the body or in the base of the container.

2. Pinhole. Any opening causing leakage. It occurs most often in bottles with pointed corners.

3. Overpress. Is a defect where a small ridge of glass has been formed on the sealing surface of the finish

4. Poor Distribution. Thin shoulder, slug neck, choke neck, heavy bottom are terms used to describe the uneven distribution of glass.

5. Soft Blister. A thin blister, usually found on or near the sealing surface. It can however show up anywhere on the glass container.

6. Cracks. Partial fractures, usually found in the finish, bend, base neck or in the heel area, example of cracks effect is the Broken Finish. A finish which has cracks or actual pieces of glass broken out of it.

7. Split. An open crack starting at the top of the finish and extending downward.

      SOME MAJOR DEFECTS    AQL= 2.50

1. Chipped Finish. Pieces broken out of the top edge in the manufacturing process.

2. Stone. Small inclusion of any non-glass material

3. Bubbles. Gaseous inclusions up to 0.8 mm diameter.

4. Rocker Bottom. A sunken centre portion on in base of the container

5. Flanged Bottom. A rim of glass around the bottom at the parting line

6. A bottom which has sagged so that the container is unstable when placed on a flat surface.

      SOME MINOR DEFECTS       AQL= 4.0

1. Sunken Shoulder and Sides. Not fully blown, or sagged after blowing

2. Tear. Similar to a check, but opened up. A tear will not break when tapped, a check will.

3. Washboard. A wavy condition of horizontal lines in the body of the bottle.

4. Hard Blister. A deeply embedded blister that is not easily broken.

5. Dirt. Scaly or granular nonglass material.

6. Heel Tap. A manufacturing defect where excess glass has been distributed into the heel.

7. Marks and Wrinkles. A brush mark is composed of fine vertical laps, e.g. oil marks from moulds. Includes baffle and shear marks.

8. Wavy bottle. A wavy surface on the inside of the bottle.

9. Seeds. Small bubbles in the glass with less of 0.8 mm of diameter (maximum tolerance of 30 seeds/kg of glass)

10. Neck ring seam. A bulge at the parting line between the neck and the body.

11. Blank and Blow mold seams. Seams which are relatively large, extending from the shoulder to the bottom of the container. Blank seams tend to veer off from the mold seam.

12. Swung baffle. The baffle mark has swung one side and is not central to the bottom of the container

13. Swab Ware – Base. Residue left in the bottom of the container from the IS Machine swabbing process.

14. Line Over. A superfine groove across the sealing surface that can cause a container leak after the filling process.

15. Offset Finish. A finish formed out of alignment, either vertically or horizontally.

16. Out-of-round and off-gauge. A finish which is oval-shape and which may be pinched or flattened.

17. Saddle Finish. A gradual slope or dip in the finish that has a saddle like finish.

18.  Unfilled finish. A finish which is incompletely filled, in the top, the bead or the thread.

19. Structural defects internal stresses in the container due to poor annealing.