Testing of canned products within metal packaging may be required for various reasons including product/pack compatibility,
spoilage assessment and integrity checks on the container and seams, mechanical strength requirements, compliance to regulations and functionality
tests. Outlined below is a non-exclusive list of common tests carried out when assessing metal packaging.
Biotesting is a form of comparative container integrity testing used particularly during the development and introduction
of new or modified forms of containers.
Containers are filled with a microbiological nutrient material and heat processed. The containers are then brought into
contact with contaminated cooling water with a known microorganism. Samples are stored and checked for spoilage.
Campden BRI has facilities for packing the containers, processing, storage and microbiological testing.
Drop tests can be conducted on packaging in various orientations and from a range of heights to determine its impact strength.
Dye penetration testing
Dye penetration testing can detect leaks in packs down to approx 10 microns and are conducted over a period of 24 hours.
These tests are especially effective for testing leaks in the seal area of the pack.
Torque testing on (bottle and jar closures) measures the amount of force required to open a jar or bottle closure must
balance the importance of closure integrity against the requirement of convenience for consumers wishing to open the packs. A Mecmesin Tornado
digital closure torque tester is used for measuring application and removal closure torques.
Strength and integrity
Seam sectioning / double seam evaluation
The production of a high-quality double seam in food cans is dependent on several factors, including conformity of the
can and end specifications; the quality of the seamer tooling and its compliance with the can and end being used and the condition of the seaming
machine and setup of the seaming rolls, lifter pressure and other components. A problem in any one of these factors can contribute to seam defects
that have an adverse effect on the ability of the can to withstand contamination and prevent the product from leaking or reduce its shelf life.
Campden BRI can conduct manual seam assessment and seam sectioning to evaluate the quality of the can seams and their conformance to
Leak testing of cans
Checking the quality of the double seam can be carried out on receipt of new containers for 3-piece cans to assess the
can makers seam or post processing/post seaming to assess the canners seam. Air pressure leak testing can be used to pressurise the can
internally with a regulated pressure and monitor the can for leakage when submerged under water. This method is often used in conjunction with
seam evaluation to allow for pin point analysis of a certain area if leakage is noted.
Side wall and vertical axis strength testing
Metal cans are often used for their rigidity and strength along with many other factors. Strength testing of cans can
be carried out to determine the top load capability by testing its vertical axis strength. Side wall strength is an important characteristic of
cans as they are required to withstand implosion and expansion during retort conditions.
Determination of vacuum present in cans
Filled cans are processed to kill off microorganisms, as the cans are cooled this creates a partial vacuum within the
can. Vacuum gauges can be used to determine the level of vacuum present within a can and if this meets the criteria which is often set by the
canner. A vacuum may also be pulled on sealing of the can if using a vacuum can seamer in which a cross check may be required to ensure the vacuum
level is at the level expected by the can seamer.
Head space gas analysis
Gas headspace analysis can accurately measure the oxygen, carbon dioxide and balance gases composition in the headspace
of sealed flexible or rigid packages, including metal packaging.
The thickness of the metal used and uniformity of the metal on cans produced using a Drawn & Wall Ironed (DWI) process
is important when assessing the metal thickness. Campden BRI has a series of Mitutoyo micrometers and can accurately measure the plate thickness
Checks against specifications
Campden BRI has a series of gauges available and accurate balances allowing for cross checks against supplier
specifications to provide an independent assessment against a specification received from the packaging supplier/manufacturer. Common tests may
include dimensional checks, weight checks, strength characteristics and physical performance properties.
Can lacquer integrity
Can lacquers are widely used to provide protection to both the product and the can and eliminate or reduce negative
product / pack interaction. For this reason, it is important that the lacquer is applied across the entire surface leaving no underlying metal
Lacquer weight determination
Lacquers and coatings are used widely to protect the can internally and externally from corrosion and to protect the
product internally from elemental transfer from the container into the product. Lacquer weight should be displayed within the final can specification
displaying a weight as g/m2. Campden BRI can carry out tests to ensure the lacquer applied meets the stated figure on the specification.
Lacquer adhesion testing
Once the lacquer has been applied it is vital that it has been cured correctly ensuring correct crosslinking and good
adhesion to the underlying metal. Lacquer adhesion testing measures whether the lacquer can be removed using a tape test set up.
Can end checks
Score line analysis
Easy open ends (EOE) are commonly used as a convenience function on metal cans allowing the consumer to have quick access
to the contents of the can. To enable this function the can end is accurately scored around the required area, thinning out the metal. This makes
the end easy to open when punctured using a ring pull tab and allows the consumer to peel away the lid. Campden BRI can cross section the score
line and measure the depth of the score line against the thickness of the can end using a scanning electron microscope (SEM) to obtain images and
Determination of compound lining weight distribution
To ensure a hermetic seal is achieved a compound lining is applied within the ends of cans which acts as a filler material
to fill any free space when creating the double seam. It is important that the compound lining is correctly and evenly distributed around the
inside of the can end as too much may cause seaming issues and too little may leave areas exposed and at risk of leakage. Campden BRI can assess
can ends to determine the total weight of the compound lining present by using accurate balances capable of weighing up to 5 decimal places.
Ring pull analysis of easy open ends
An easy open end (EOE) is applied to cans to provide a convenient function to allow consumers to easily open the end and
provides full access to the food. An important factor based on this would be the force required to open the can. Campden BRI can carry out testing
on ring pull cans to determine the force required to open at two test conditions including a 90°peel and a 45° peel.
Corrosion assessment and investigation
Scanning electron microscopy
Scanning electron microscopy offers imaging, mapping and elemental analysis which help with the examination of defects
such as pin-holing, stress cracks and breaks in the lacquers. Imaging at high magnifications can help identify and visualise the type of defect.
These images can then further help to identify if the defect originated externally or internally and if the integrity of the material has been
Elemental analysis and mapping can help identify the presence and distribution of compounds that may have contributed to
the defect, such iron rust or the build-up of chlorine. This analysis would also demonstrate the break in lacquer and exposure of the underlying
You may also be interested in
The Campden BRI group companies listed below are both accredited in accordance with the recognised International Standard
ISO17025:2017 by the United Kingdom Accreditation Service (UKAS). The accreditation demonstrates technical competence for a defined scope of methods,
specific to each site, as detailed in the schedules of accreditation bearing the testing laboratory number.
The schedules may be revised from time to time and reissued by UKAS. The most recent issue of the schedules
are available from the UKAS website www.ukas.com
Campden BRI (Chipping Campden) Limited is a UKAS accredited testing laboratory No. 1079
Campden BRI (Nutfield) is a UKAS accredited testing laboratory No. 1207