chollie

The screener isn't obligated to allow an item through, even if it passes all tests. Screeners can deny any item without a specific reason.

Screeners have been trained to be particularly suspicious of opaque liquids/gels because even if they are in a clear container and pass an ETD test, they allegedly could conceal hidden dangerous items - maybe a 3" knife or a miniature gun, for example. This is why it is impossible to 'clear' a jar of peanut butter and why screeners stick their fingers in cremains: think of all the dangerous items that could be concealed by the peanut butter (or breast milk or cremains) that could be used to take control of an aircraft.

Makes you wonder how they clear cakes and muffins without breaking them up to be sure there's no hidden weapon inside like the jail-breakers used to do.