I might not be a must, but I definitely keep mine in the fridge with the gh. I figure better to keep it constantly cold even when initially mixing. If the bac. water is room temp then the gh will be warmed until it is recooled in the fridge. I don't know if this could have any degrading effect, but as much dough as I pour into gh, I'm not taking any chance I don't have to. I say Lawnsaver is most likely right, but I'd still keep the bac. water cold. Why not?