I just received my packet of San Francisco Sourdough Starter from Sourdough International. The instructions call for a proofing box for the first five days. Is this absolutely necessary? I have a Styrofoam cooler but don't want to have to run to the hardware store and get the light socket, etc. Anyone have luck growing this starter without constructing the proofing box? I don't want to experiment with this starter since it's pricey.
Thanks for your input!