There is much debate as to the ideal ratio of vermouth to gin in a dry Martini but there is uniform agreement that a very cold serving temperature is essential. Enter a technique called Supercooling (or Undercooling) pioneered by Giancarlo Mancino of Mancino vermouth fame.
Supercooled water is water that is on the very edge of freezing, held at a temperature just above its freezing point. This is poured into a frozen glass over a frozen olive. The very olive causes the water to freeze instantly on contact so as the water is slowly poured it forms a stalagmite which rises from the base of the glass. Vermouth is then atomised over the drink and frozen gin poured. The speared olive is used to stir the drink which is finished with a spray of orange zest oils. The result being a Supercooled Dry Martini with all the theatre, but without the risks, associated with liquid nitrogen Martinis.
The science behind this revolves around the purity of the water and holding it at a temperature that is fractionally above its freezing point. Turing water into ice, a very different structure which is 8% less dense, requires cooling to a temperate below 0°C and the purer the water, so the colder that temperature as freezing water molecules form around these impurities. Hence, fewer impurities make it more difficult for ice to form. Liquids are unstable at temperatures below their freezing point and putting such a supercooled liquid in contact with something colder will instantly force them to freeze – sometimes called “snap freezing”.
Giancarlo uses a purpose made refrigerator, Supercooling Magic, available from Barcelona based Fujisakura to supercool the water he uses and hold it at the perfect temperature. However, with some trial and error, you can achieve the same result with a standard freezer.
Fill a plastic bottle with filtered or distilled water and place this in a chest freezer alongside another bottle filled with tap water. Due to the impurities in the tap water, this should freeze just before the filtered water. With constant checking and a lot of patience, you should be able to judge the moment when the tap water is frozen but your filtered water is in a supercooled liquid state. Or, invest in a Supercooling Magic refrigerator.