Originally Posted by jeepinjeepin
It will always freeze. You just need a colder freezer....or dry ice.
I knew, in theory, you were correct so I was curious. I found these numbers. (I haven't verified them though) This might at least give you an idea of what proof you are getting from the temps in your freezer.
So if you know the temp in your freezer and you are still getting a frozen product...
24 proof liquor freezes at -6.7°C (20°F)
64 proof liquor freezes at -23.33°C (-10°F)
84 proof liquor freezes at -34.44°C (-30°F)