Last fall, we made some grape jelly from some seedless red grapes we bought at the store. The fruit was nice and juicy and ripe with no bad fruit. We washed it and then put it through a food mill to keep the seed and skin out. We used sugar, pectin and lemon to make the jelly. It turned out beautifully and quite tasty. One of my customers said that after she has had hers open a few weeks, it has started to crystalize. Can someone tell me if they have any ideas as to why that is happening. I have been making jellies and jams for several years and have never had anything crystallize. Thanx in advance for your input.