I've just stumbled across this forum having started a bit of a sourdough experiment. I think I might have the opposite problem of most people when creating the starter - it is extremely active after only 20 hours or so.
I mixed organic unbleached white flour, water and some crushed red grapes (in a muslin bag submerged in the mix) and put it in the cupboard above the hot water tank, which is pretty warm. I now have a very bubbly and fluffy mix, with a darker liquid layer part way down and then a pale beige layer under that. It at least doubled in size and smells sweet and a bit off - kind of like baby vomit. Not really rotten but a bit like fermented or 'on the turn' fruit.
My recipe said that it should take 10 days to a fortnight to get even some bubbles and signs of activity, and not to start feeding the starter until that happened.
So, my question: is there something wrong with the starter, or has it just gone much quicker than anticipated? Shall I throw it out and start again? Leave it for the 10 days recommended in the recipe? Or start feeding it now?
I have taken it out of the warm cupboard and it is in the kitchen, which fluctuates between about 17 C and 3 or 4 C (when the heating is off overnight).
I hope you can confirm that this has just gone much quicker than expected, but if it's gone wrong, I'd like to cut my losses and start again asap.