Jam yesterday, jam tomorrow

I've just been struggling to open a jar of 2013 strawberry jam -- while the summer that bore fruit in those strawberries is long gone by, and indeed the actual maker of the jam is since dead, the home-made preserves, once I had managed to break the unintentional vacuum seal on the lid, are still as fresh as they were when they were first put into the larder to set.

Boiling hot sugar is a remarkably effective preservative.