I haven't made blueberry, but if you want to try a delicious and a little different peach marmalade, take 7 #'s peaches, don't peel them, just chunk them up and throw in a few pits in the kettle too. Helps prevents sticking. Add 4#'s sugar and 1 cup cider vinegar and simmer till its thick and sort of translucent looking. I have even done it in a crockpot and while they turn darker, its still GOOD eatin!!!!!!!! Put in jars, and while I don't water bath them, I suppose you could, I just put paraffin on mine. Talk about heaven on earth when its cold and snowy and you have fresh hit biscuits and Grandma's peach marmalade. My mom called it peach butter too . . .but I think marmalade sounds nice!!!