Lowering the freezing point of water is easy where you can just add a solute. Raising it is difficult there are 2 known ways: adding electricity or alcohol/testosterone. Adding alcohol to the water, however, changes its behavior. When cooled, alcohol forms ice-like hexagons, and the water droplets coalesce around these instead of floating freely around each other. The hexagonal structures provide the same type of stability as solid impurities. By adding alcohol, scientists have found they can raise the freezing point of pure water to 0 C. Adding electricity by placing electric cells in a humid room and turning down the temperature until water starts to condense on the pyroelectric crystals. After doing so it is concluded that droplets froze at -12.5 C (9.5 F) on an uncharged surface, but on a positively charged surface, they freeze at -7 C (19.4 C). On a negatively charged surface, the water freezes at -18 C (-0.4 F).
