Reminds me of the time when a couple of days before my wedding, my friend that was visiting from Holland and I went blackberrying - it was a beautiful September day, every one else was at work.
Got the blackberries home - we only had a small freezer so decided to make jam. It wouldn't set , so my mum's (old ) recipe book said to add cream of tartar, which we did and it finally reached setting point!
Jam cooled, put into jars and it did seem a bit thick.
My friend took a jar back to Holland with her and 6 months later I and my new DH visited her at her home - her mum got this jar of jam out of the fridge and asked if we would like a slice !!
Don't know what happened to the other jars full - they mysteriously disappeared while we were on honeymoon !