[shokkyy]

So if I've got old jam jars that had pop-up lids on, can I pressure seal those lids again or do I need to buy new lids?

[mumofstig]

Carry on using them till they get rusty  

[Jamie Butterworth]

i resused mine today, they were fine, and id didnt expect the bit on them which indicates if they have been opened or not bu popping it would reseal its self

[shokkyy]

Well I'm puzzled then. I've been making jars of passata from my tomato glut for several weeks now. Today I checked the jars, and all those jars with new lids are still fine. All the jars with reused lids have gone back up, and one is even growing fur on the passata. I have to assume that all those jars with the lids back up now need to be chucked away.

So if it's not the reused lids, I wonder what else has caused this. I've done every jar in exactly the same way and all the lids popped as they should do.

[mumofstig]

I've just been and checked all my jars of passata and they are all still 'seals down' so I don't know what happened to yours 

Did you sterilise the lids in boiling water before you put them on....mind you the boiling of the jars should sort that out anyway........erm?

[shokkyy]

I've just been and checked all my jars of passata and they are all still 'seals down' so I don't know what happened to yours 

Did you sterilise the lids in boiling water before you put them on....mind you the boiling of the jars should sort that out anyway........erm?

Any jar I reuse goes through the dishwasher, and it gets pretty hot in there. And just before using, yes, I sterilise all jars in the microwave and pour a bit of boiling water on the lids.

[Ice]

It's the heat that creates the vacuum that makes the pop up go down.  If it has gone up then the vacuum must have been broken in some way. 

[shokkyy]

Maybe I didn't do the lids up tightly enough? Does seem a big coincidence that it happened only on reused jars and not on new ones. Perhaps the newer lids just want to go on tighter, but for the old ones I need to put a bit more muscle into it. A couple of the jars with broken seals actually had rings of passata around the base of them, kind of like they'd had a minor explosion and started leaking.

[Madame Cholet]

I get the od jam or chutney doesn't pop I put them in the fridge and use them first. I lay in bed and hear them popping at night.