c. Excessive Flux. This is a can with excessive flux on the ends or sides of the
can. It is a minor defect. Traces of flux at edges of soldered areas are normal in can
manufacturing. It is considered excessive if there is enough to cause corrosion.
d. Leaker. A leaker, or leaking can, is a can with a puncture or with rust spots
that have perforated the tin or with an incomplete closure of a seam. This defect usually
is a progression of other defects and is noted by food contents on the outside of the
can, loss of vacuum, absence of the contents of the can, or actually seeing a large
perforation. This is a critical defect.
2-13. INTERNAL DEFECTS
An internal or open-package examination of containers may reveal defects not
seen otherwise or may reveal the cause of defects observed during external
examination of the container.
a. Spangling. This is a dark discoloration of the interior can body as a result of
high acid foods reacting with the tin plate during storage. If the acid is of a certain type,
gas will be formed and a sweller will result which is seen during the external
examination of the can. Spangling resembles the appearance of a galvanized bucket
with the mottling of light and dark colors. The defect may be insignificant or it may be a
minor or major defect.
b. Detinning. This is much darker than spangling and is normally on one end of
the container or covers the whole interior body. The body has reacted with the product
to remove the tin plate and has exposed the steel base plate. The defect may be
insignificant or it may be a minor or major defect.
c. Fractured Enamel. This defect is the result of areas of the tin plate not being
covered with enamel. See Figure 2-9. Scarred enamel is the result of imperfect
polishing or rolling of the tin plate leaving longitudinal scratches which are not filled with
enamel. When enamel chips or flakes off the tin plate, the defect is called flaked
enamel. This is the result of a poor baking process or the presence of dirt, water, or
grease on the tin plate prior to application of the enamel. The defect may be
insignificant or it may be a minor or major defect.
d. Pinholing. Pinholing is an internal defect caused by acid product eroding the
tin plate. It will be seen either as small pits on the inside of the can or as a leaker if the
defect is extensive. It is a critical defect.
e. Flat Sour. This defect occurs when the contents of a can have soured or
spoiled even though the can has not swollen. It is caused by microorganisms
decomposing the product without the formation of gas. It is a critical defect.
MD0708
2-16
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