Yeah mine is set to -1, which is a degree less than the default. -10 seems unusually low to set a home freezer. I used to keep bottles in the freezer but never had one freeze up at all on me or show any ice crystallization. If there was a difference, it may have slightly thickened in viscosity. The freezing point of 80 proof is about -17F.
Does 80 proof alcohol kept in the freezer have the same coolant properties as the equivalent of ice?
I do not know about Alcohol but if I remember right, the heat required raise ice one degree and water one degree is one BTU. (British Thermal Unit) to raise 1 pound of ice from 32F to water at 32F is 144 BTUs.
So if we assume that the same heat is required with Alcohol then one pound of Alcohol. Then 1 pound of Alcohol stored at 0F will take 32 BTUs to get to 32F (assume on ice is bottle), then on to 70F another 38 BTUs. Total 70 BTUs.
1 pound of ice at 0F will take 32 BTUs to get to 32F. Then 144 BTUs to turn into water no ice. Then another 38 BTUs to get to 70F. Total 214 BTUs. About 3 & 1/2 times more cooling with ice.