After a false start last weekend on my first AG batch (bad thermometer that was reading 191 on a rolling boil so I never started), I plan to tackle it this weekend with Beirmuncher's Blue Balls Wit. However, my digital thermometer under the stairwell in my basement is reading on average 73 degrees, which is too warm. If I went with the wet towel method over the glass carboy, how low can I expect it to get?