Openability of vacuum lug closures.

The Vacuum Lug Closure system, or VLC, is found on many widely available products such as jam, sauces and pickles. The closure has many useful advantages over other closure systems, and it is popular with both manufacturers and consumers. However, there are large groups ofpeople that have great difficulty opening products packaged in jars with vacuum lug caps. The goal of this project is to understand both the way in which consumers interact with the closure, and also how the closure system works. The torque that users can apply to ajar lid was measured using a torque sensor embedded in a modified jar. This was then compared to a calcula~ed torque derived from grip measurements. This second type oftest can be used to predict openability for any kind of closure by utilising simple and quick tests and mathematically adapting strength test data. By eliminating the need to perform more extensive tests, costs are kept to a minimum whilst ensuring that the results are still relevant to the problem. The results from both tests were compared with the measured forces required to open examples ofconsumer packaging found on sale. The results from both tests agree reasonably well, but more data is required regarding the interaction between human skin and packaging materials. However the current required opening torques were found to be far too high for many users. It is suggested that a limit of 1Nm torque should be used for future packaging designs to allow over 97% ofthe UK population to openjars. The optimal diameter ofjar lid was found to be 73 mm.