QUOTE ( @ 2009-06-01)
What could be the problem if there\’s a leak next to the pull tab?

Pull tabs can cause problems with any induction seal system. They do two things: since the currents we induce into the foil like to travel along the outside edge of the material, they give that current a path that is not directly above the land area, so they create the heat somewhere other than where you want it. And, they also act as a bit of a heat sink that robs some of the heat that would normally go to the land area. You can counteract this to a certain extent by reducing the size of the pull tab to the minimum acceptable size. We’ve also had some success with folding the tab back onto itself. Lastly, you can experiment with shapes of the tabs to minimize these effects.

QUOTE ( @ 2009-06-01)
Swirling pattern on larger diameter closures more common than smaller diameter closures?

They are more common on larger containers simply because the foil is larger, so it is more difficult to get heat into the center of the foil. Induction generally focuses the heat towards the outer edges and relies on heat conduction through the foil to get the heat into the center.