Ice wine can be made only from grapes that are frozen several degrees below zero — a requirement that makes ice wine a rarity.

I’m standing here in the cold where a blizzard has just dumped three feet of snow in my backyard, but I’m here to talk to you about ice wine, a dessert wine that is produced only when weather conditions are absolutely perfect.

See, what you need is a location that’s warm enough in the summer and fall to grow the grapes, and cold enough in the winter to freeze them. Kind of like, well, my backyard.

Here’s how it works: when the thermometer hits seven or eight degrees below zero, the winemaker rushes out to the vineyard, picks the grapes by hand, rushes back to the winery and presses them while they’re still frozen. Why do they need to be frozen? Well, the answer lies in my favorite subject, chemistry.

A grape is mostly water, sugar, and flavors... kind of like my stomach on a Friday night, but that’s not important. What matters is that water has a dirty little secret. In its liquid form, water is like a public golf course. Anyone is allowed to play. Sugar, salt, acids, bases, what have you. But, when water freezes, it turns into an exclusive country club, thumbing its nose at those other molecules. Only H2O is allowed in.

So that means that when the grape freezes, it’s actually just the water inside the grape that’s freezing. All the good stuff: sugar, acids — the components of flavor — are left out.So, when those frozen grapes are crushed, all that water-turned-ice is left in the press, and what comes out is an incredibly concentrated juice that is fermented to make ice wine. The result is an elixir as sweet and racy as a first kiss. And that is how weather makes wine.

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