I made a sourdough rye starter. I had it a place that got too cold so I moved it into a warm space (180 deg F). It did not do much as Rose says for a couple of days. I could not bear to throw away the 1/2 I was supposed to discard upon the first refreshment so I used that to start a bread flour (white) starter-levain-barm. On the third day, it started to grow and by the fifth day, it went to the top of my Mason jar. So I refreshed them and after an hour stuck them in the fridge for the every three day refreshment. In two weeks, I’ll make a rye and a white sourdough bread. I am going for a quite sour bread, which I really like.
So finally, I would not fuss with grapes. There is plenty of something in the flour (rye) that makes the starter rise. I did use a tip from the Baker’s Apprentice (Peter Reinhart) to use unsweetened pineapple juice as the liquid for the first two days. It is supposed to eliminate harmful bacterial growth that spoils the batch.
And more finally than the last, this is really fun. I have baked so much bread lately, I have to give it away. Rose is a great teacher. Just do what she.says. All will go well.