Overset Jam - How do I rescue it, and what causes it?

[SerendipityAlways]

Made some plum jam this evening which has overset. How do I rescue it please and can someone expain to me why it happens? I used a sugar thermometer and boiled it to 105 degrees as required, so I didnt think I had over boiled it. Thanks!!

Bump - all help appreciated!!

What do you mean by overset? Solid enough to slice?! Tbh I'm not sure there is anything you can do to save it, I've never come across it before. Let me have a quick google.

Okay have a had a quick scout round. Most obvious thing to try is to use one jar and attempt a reboil - scrape out the contents into a pan and slowly add a little bit of hot water to thin the mixture. Beat it in and reboil to setting point tests as usual. Pour into fresh sterilised jars. An alternative is to take out just enough to use as a sauce for ice cream or yoghurt. Put a spoonful or so per person into a microwaveable bowl, beat in enough hot water to thin and then warm gently.

Thanks sparkle - by overset, I mean the jam is quite solid in the jar, I would have expected it to drop off a spoon, but this consistency of jam wouldn't! I'll give that a go !

Thanks Polter - I used ordinary granulated sugar and some water and nothing else. I'm hoping to make another small batch this week, so do you think I should boil it for less time to ensure I get the right consistency?

PS - Sparkle I also meant to say I reboiled one of the jars I'd made earlier and added boiling water to thin it out. Then added the jam to a new sterilised jar. Had a look at it this morning and its a lovely consistency, not thick at all!! Thank you

Oh I am pleased! Plum (and damson) are probably my favourite jams of all!