The sourdough starter I'm trying to make (from The Village Baker) is quite a firm little ball and has such a thick crust on it that I don't see how it can possibly grow or form bubbles. It's day 3, and it should be showing signs of life.  The recipe said to cover it with a damp cloth, but nothing about keeping it damp, so I let it dry out. Mistake?   I could play with any of these factors at this point - an airtight lid instead of cloth, warmer or cooler temp, higher hydration of dough. I'd like to know how others have managed with this recipe. 

Thanks, Doh!