Canning and Fish Packaging Technology

Unit 14 - Glass containers and Closures

14.1.6.Flaws or defects
In glass containers the outer surface is less strong than the inner surface (which is smooth) as the former is blown against a metal mould. Fracture occur where are origin on the surface is subjected to sufficient tension. Three main types of origin or flows are

• Griffiths flows (submicroscopic)
• Check or fissures ( less than 10 cm length): Happens during handling in the first to three stages of manufactures. Such a defect should be less than 1 in 500 containers).
• Abrasion scuffing

Other defects in the glass containers may be seen by the naked eye are categorized into critical, major and minor faults.

Critical faults are defined as those which could contaminate the product or prove hazardous to the person using the container,
e.g. 1) Bird cage 2) Spike 3) Glass inside (piece of glass).

Major faults are defined as those which affect the performance of the container,

e.g. 1) Split base 2) Cracked ring 3) Unfilled ring 4) leaners.

Minor faults are defined as those which do not affect the performance of the containers but detract from its visual appearances,
e.g. washer board, blank seams, wedged base.