open a kilner jar

[limetree]

I have been given a kilner jar filled with maramalade which won't open. It is the wire over a glass lid type.

[Fitzer]

It's probably the vacuum in the jar holding it shut, you need to use something like the round end of a table knife to work between the rubber ring and the glass, this should allow air in and it should open easily. If it is a commercially filled jar there might be a tab (not the big one) on the rubber ring that you cut off to reveal a small hole which will perform the same function as above.

[parkesquay]

It may help to pour very hot water, say direct from a kettle or even a hot tap, onto the lid. This will cause the lid to expand and thus release some pressure.