Later that afternoon I went to another lecture, about ice, in all its varieties: frazil, grease, brash, shuga, pancake, white, drift, rafting and fast.
An alternate procedure is to soak the affected areas in an iced 0.13% water solution (1:750) of Zephiran chloride (benzalkonium chloride solution, NF).
First, the solid ice on the surface could have been annealed, meaning that its temperature could have been raised above the 78 Kelvin mark to allow the amorphous ice to recrystallize.